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7 January 2014 DNA Damage Response Genes and the Development of Cancer Metastasis
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DNA damage response genes play vital roles in the maintenance of a healthy genome. Defects in cell cycle checkpoint and DNA repair genes, especially mutation or aberrant downregulation, are associated with a wide spectrum of human disease, including a predisposition to the development of neurodegenerative conditions and cancer. On the other hand, upregulation of DNA damage response and repair genes can also cause cancer, as well as increase resistance of cancer cells to DNA damaging therapy. In recent years, it has become evident that many of the genes involved in DNA damage repair have additional roles in tumorigenesis, most prominently by acting as transcriptional (co-)factors. Although defects in these genes are causally connected to tumor initiation, their role in tumor progression is more controversial and it seems to depend on tumor type. In some tumors like melanoma, cell cycle checkpoint/DNA repair gene upregulation is associated with tumor metastasis, whereas in a number of other cancers the opposite has been observed. Several genes that participate in the DNA damage response, such as RAD9, PARP1, BRCA1, ATM and TP53 have been associated with metastasis by a number of in vitro biochemical and cellular assays, by examining human tumor specimens by immunohistochemistry or by DNA genome-wide gene expression profiling. Many of these genes act as transcriptional effectors to regulate other genes implicated in the pathogenesis of cancer. Furthermore, they are aberrantly expressed in numerous human tumors and are causally related to tumorigenesis. However, whether the DNA damage repair function of these genes is required to promote metastasis or another activity is responsible (e.g., transcription control) has not been determined. Importantly, despite some compelling in vitro evidence, investigations are still needed to demonstrate the role of cell cycle checkpoint and DNA repair genes in regulating metastatic phenotypes in vivo.


DNA is continuously damaged by genotoxic agents generated either in the environment (e.g., UV light, ionizing radiation, etc.) or intracellularly (e.g., reactive oxygen species as byproducts of routine metabolic processes). In normal cells, the integrity of the genome is ensured by a very efficient DNA damage response signaling network that includes cell cycle checkpoints and DNA repair pathways. On the other hand, cancer cells are thought to arise through the accumulation of numerous genetic alterations that confer growth and survival advantages. Dysregulation (either loss or gain) of DNA repair factors can promote the accumulation of DNA errors and genomic instability, which is implicated in aging, immune deficiencies, neurodegenerative disorders and cancer. Germline mutations in cell cycle checkpoint or DNA repair genes can predispose to hereditary forms of cancer, whereas somatic mutations and epigenetic silencing of DNA damage response genes are common in cancers with no inherent genetic link (1). DNA repair genes involved in nucleotide excision repair (2), mismatch repair (3), non-homologous end joining (4, 5) and homologous recombination (6) can predispose to different types of cancer.

Dysregulation of DNA repair genes affects the response of cells to DNA damaging anti-cancer treatment. Upregulation of DNA repair pathways can cause resistance to chemotherapy and radiotherapy, so inhibitors of these pathways have the potential to sensitize cancer cells to these agents (7, 8). Conversely, cancer cells that have lost a repair pathway and are solely dependent on another, alternative pathway, can be rendered vulnerable by targeting the functional pathway using the principle of synthetic lethality, whereas noncancer cells (with two functional repair pathways) would demonstrate resistance (7, 8).

In recent years, there has been accumulating evidence that DNA damage response genes are involved in additional cellular functions beyond mending damaged DNA and cell cycle checkpoint control, such as transcriptional regulation, chromatin remodeling and apoptosis. In this article, we provide an overview of the evidence that DNA damage response (DDR) genes participate not only in tumor initiation, at least in part when they fail to ensure proper repair of damaged DNA, but in tumor progression and metastasis as well.


Genomic instability is characteristic of most human malignancies and it is considered a hallmark of cancer cells. Genomic instability is caused by downregulating DNA damage response pathways, such as those controlled by p53, ataxia telangiectasia mutated (ATM) and AT and Rad3-related (ATR) kinases. Alternatively, genomically unstable tumors can arise from acquired defects in any one of six DNA repair or damage tolerance pathways, base excision repair (BER), nucleotide excision repair (NER), DNA mismatch repair (MMR), homologous recombination repair (HR), non-homologous end joining (NHEJ), and translesion DNA synthesis (TLS). The connection between DNA repair defects and carcinogenesis is highlighted by the fact that inherited defects in DNA repair mechanisms that cause progeroid or accelerated aging syndromes (9), including Ataxia telangiectasia, Nijmegen syndrome, Werner syndrome, Bloom syndrome, Rothmund-Thomson syndrome, Xeroderma pigmentosum or Trichothiodystrophy also carry a higher cancer risk as well (2, 10).

In addition to DNA damage response gene mutations, which can either be inherited or somatically acquired, epigenetic gene silencing may also promote tumorigenesis. Epigenetic inactivation of DNA repair genes in cancer has been reported and has been related to several DNA repair pathways including BER, NER and other DNA damage processing mechanisms (11). In sporadic cancers, one of the most common mechanisms of inactivation of DNA repair pathways is the epigenetic silencing of a critical gene (e.g., FANCF, BRCA1) through methylation of the promoter region. Epigenetic silencing of DNA repair genes, such as MGMT, MLH1, BRCA1, WRN and FANCF, can boost mutation rates and promote genomic instability in cancer cells (12). Below is a brief description of the connection between specific aberrant DNA repair pathways and human cancer.

Direct Repair

The simplest form of DNA repair is the direct reversal of a lesion. MGMT (O6-Methylguanine DNA methyltransferase) participates in this kind of pathway and is often at higher levels in tumors compared with normal cells where it can confer resistance to DNA-alkylating agents. The MGMT enzyme repairs O6-alkylated guanine residues in genomic DNA. O6-methylguanine pairs with thymine and would lead to a G-to-A transition during DNA replication if left unrepaired. MGMT is epigenetically silenced (13) in a variety of tumors, including glioblastoma (1416), colon cancer (17, 18), non-small cell lung cancer (19, 20), gastric carcinoma (21), and head and neck squamous cell carcinoma (2224). In the case of colorectal cancer, MGMT promoter methylation is associated with G-to-A mutations in KRAS (25) and in p53 (26).

Base Excision Repair

The base excision repair (BER) pathway is the main mechanism that protects the genome from deleterious effects of exposure to reactive oxygen species. This pathway removes damaged bases from DNA and it can also repair DNA single-strand breaks (27). A number of DNA glycosylases (e.g., OGG1: 8-oxoguanine DNA glycosylase; MUTYH: the human homolog of the E. coli mutY gene), endonucleases (APE1: apurinic/apyrimidinic endonuclease 1; FEN1: flap structure-specific endonuclease 1), XRCC1 (X-ray repair complementing defective repair 1), DNA polymerase β (Polβ), DNA ligase III and PARP-1 participate in this DNA repair pathway.

Inherited mutations in BER genes are rare. However, polymorphisms in genes like OGG1, APE1 and XRCC1 have been genetically linked to cancer (28). MUTYH, (29) is the first BER gene to have been associated with a human cancer syndrome (MUTYH-associated polyposis), as biallelic germline mutations in MUTYH were identified in individuals with a pre-disposition to multiple colorectal adenomas and carcinomas (30, 31). Other DNA glycosylases are also found dysregulated in various cancers. For example, OGG1, which repairs oxidatively damaged guanine bases in DNA, is involved in tumorigenesis (3234), whereas expression of the thymine DNA glycosylase gene (TDG) is decreased in several multiple myeloma cell lines compared with normal plasma cells by promoter methylation (35). Production of APE1, an enzyme that follows the action of DNA glycosylases in the BER pathway, is frequently increased in germ cell tumors (36), and higher APE1 protein levels have been associated with increased drug and radiation resistance (36, 37). Further downstream in the BER pathway, Polβ, which is the major DNA polymerase that fills in the nucleotide gap created by APE1, is overexpressed in prostate, ovary, uterus and stomach cancers (38), as well as prostate, breast and colon cancer cell lines (39). In addition, elevated levels of Polβ lead to genomic instability through the accumulation of DNA single- and double-strand breaks (40, 41), and these effects are particularly evident after exposure of Polβ-overexpressing cells to oxidative stress-inducing DNA damaging agents (42).

FEN1, which participates in BER (43), non-homologous end joining (44) and homologous recombination (45), and is important for genomic stability (46), demonstrates increased expression in many tumors. It is highly abundant in testis, lung and brain tumors (47) and in prostate cancer (48), metastatic prostate cancer cells (49), neuroblastomas (50) and pancreatic cancer (51). In breast cancer, this increase is due to the absence of FEN1 promoter methylation (52).

Finally, glioblastoma cells overexpressing EGFRvIII, an oncogenic variant of epidermal growth factor receptor (EGFR), become hyper-dependent on a variety of DNA repair genes (53), including an enrichment of base excision repair genes required for repair of reactive oxygen species-induced DNA damage. One example is PARP-1 (53), which generally shows higher abundance in tumors. Besides PARP-1, other BER enzymes (TDG, OGG1) were also upregulated in EGFRvIII-containing cells after radiation exposure. The increased reliance on BER in these cells suggests the presence of elevated reactive oxygen species levels abundance cells with resultant genomic instability.

Nucleotide Excision Repair

The nucleotide excision repair (NER) pathway is a major DNA repair process that safeguards genome integrity by repairing numerous DNA modifications, especially bulky helix-distorting damage (54). However, recent work has revealed that some proteins in NER have activities that go beyond DNA repair and include nucleosome remodeling, histone ubiquitylation, and transcriptional activation of genes involved in nuclear receptor signaling, stem cell reprogramming and post-natal mammalian growth (55).

Tumors with enhanced NER have an intrinsic resistance to radiotherapy and chemotherapy (56), leading to continued growth and metastasis after treatment (57). On the other hand, NER is often disrupted in testicular germ cell tumors due to loss of XPA expression (58). Likewise, XPC, a critical component of global genome NER, is controlled by promoter methylation in bladder cancer (59). In addition, ERCC1 is also inactivated through promoter methylation in glioma tumors (60). Moreover, mutations of XP (xeroderma pigmentosum complementation group) A, B, C, E, F and G have been found in skin and testicular cancer, and variant expression of ERCC1 (excision repair complementation group 1) or XPD was demonstrated in lung cancer (61).

Mismatch Repair

Mismatch repair (MMR) targets incorrectly paired nucleotides introduced accidentally by DNA polymerases or after treatment with base-modifying chemotherapeutic drugs (e.g., alkylating agents) (62). MMR disruption causes microsatellite instability (MSI), a form of genetic instability associated with cancer. Familial cases of colonic tumors with MSI in Lynch syndrome result from germline mutations in mismatch repair genes, primarily MSH2 and MLH1 (63). However, most MSI-high tumors arise from an epigenetic defect in sporadic cases of cancer (64). Methylation in the promoter region of MLH1 correlates with decreased activity in sporadic colon cancer (65, 66). Likewise, MLH1 is also controlled by aberrant methylation in sporadic endometrial carcinoma (67), gastric cancer (68) and many other cancers.

Homologous Recombination

DNA double-strand breaks (DSBs) pose the most serious threat among all genotoxic assaults to the survival of cells and are repaired by either homologous recombination (HR) or non-homologous end joining (NHEJ). HR is disrupted in breast and ovarian cancer (69). BRCA1 and BRCA2, two important players in the HR pathway, are mutated in early onset breast and ovarian cancer (70), prostatic (71) and pancreatic cancer (72). Loss of BRCA1 expression by promoter hypermethylation is also seen in nonhereditary breast and ovarian cancer (73). In addition, the gene that encodes NBS1, which along with MRE11 and RAD50 constitute a heterotrimeric complex that senses DNA damage mainly in the form of double-strand breaks (74), is often mutated in lymphoma (Nijmegen breakage syndrome) (75). However, loss of NBS1 expression is found in prostate cancer (76). Additionally, RAD50 frameshift mutations, which result in a truncated protein, occur in a third of gastrointestinal cancers (77). The Fanconi Anemia/BRCA pathway, which repairs DNA crosslinks (74), is often impaired in a number of hematogenous and solid tumors. Thus, homozygous mutation of numerous FA genes (A, B, C, D1, E, F, G, I, J, L, M and BRCA2) or heterozygous mutation of some FA genes (e.g., FANCA, FANCC, FANCG and BRCA2) has been shown in hereditary breast, ovarian, cervical, prostatic, lung, pancreatic, gastric cancers, as well as melanoma and leukemia (78).

Non-homologous End Joining

DSBs are predominantly repaired by non-homologous end joining (NHEJ). The gene encoding DNA ligase IV, a major mediator of this pathway, is mutated in leukemia (Lig4 syndrome) (5), whereas Artemis, a structure-specific endonuclease, is mutated in lymphoma (Omenn syndrome) (4). Loss of Ku70 expression in cervical, rectal and colon cancer has also been reported (7981), whereas Ku86 protein abundance is reduced in some rectal cancers (80).

Translesion DNA Synthesis

The translesion synthesis (TLS) machinery bypasses DNA adducts during DNA replication with the help of low stringency DNA polymerases (β, ι, κ). As mentioned above, Polβ is overexpressed in prostate, ovary, uterus and stomach cancers (38), whereas Polι is overexpressed in breast cancer (82) and Polκ is overexpressed in lung cancer (83). Elevation in expression and activity of the error-prone polymerase, Polβ, accounts for the increase in cisplatin resistance and mutagenesis of many cancers (84).


Cell cycle checkpoints are activated to arrest transiently cell proliferation, allowing extra time to repair DNA damage. When lesions are repaired, cells resume cell cycle progression (checkpoint recovery). However, when damage is irreparable cells either remain permanently arrested (senescence) or undergo programmed cell death (74). Defects in cell cycle related DNA damage response pathways result in genome instability and lead to carcinogenesis. Central to the DNA damage response are members of the phosphoinositide 3-kinase (PI3K)-related protein kinase family, ATM, ATR (ATM and Rad3-related), and DNA-PKcs (DNA protein kinase catalytic subunit) that sense the damage, and amplify the signal by phosphorylating numerous downstream substrates, including checkpoint kinases 1 and 2 (74). Activation of the upstream kinases require recognition of the damage. For DSBs, this is achieved by the heterotrimeric MRE11-RAD50-NBS1 (MRN) complex that directly binds to the exposed ends of DNA, recruits ATM and initiates its activation (85). Active ATM phosphorylates histone variant H2AX, which serves as a docking site for MDC1 (86) and many other proteins, including 53BP1, RNF8, RNF168 and BRCA1 (87).

Single-stranded DNA lesions generated from stalled replication forks are rapidly coated by replication protein A complexes, which then recruit ATR and its binding partner ATRIP (88), and independently Rad17 that in turn recruits the heterotrimeric RAD9-RAD1-HUS1 (91-1) complex to the site of damage. Subsequently, ATR phosphorylates the 9-1-1 complex, then RAD9 binds TopBP1 and RHINO (89, 90), which enhance ATR activity. Active ATR phosphorylates many substrates, including CHK1, an event important for establishing the cell cycle checkpoint (91).

Transition between the different phases of the cell cycle is dependent on cyclin-dependent kinases. Their activity is negatively regulated by WEE1 and MYT1 kinase mediated phosphorylation and, conversely, they become activated by the CDC25 phosphatases that dephosphorylate the inhibitory phosphorylations (92). After DNA damage, CHK1 induces CDC25A degradation by phosphorylating CDC25A and targeting it for proteosomal degradation (93). Alternatively, CHK1 activates WEE1 or NEK11 that further phosphorylates CDC25A, again preparing it for degradation (94). CHK2, although redundant for checkpoint activation in p53-proficient cells, becomes important for IR-induced cell cycle arrest in p53-deficient cells (95). Another mechanism implicated in G1 checkpoint induction is rapid degradation of cyclin D1 and release of cyclin-dependent kinase inhibitor p21waf1/cip1, culminating in cdk2/cyclin E inhibition and blocking G1/S transition (96). Cyclin D1 destruction is induced by GSK3β phosphorylation and SCF-dependent proteosomal degradation (97) or direct phosphorylation of the F-box protein FBXO31 by ATM (98).

CHK1 is crucial for maintaining genomic stability as it is required for monitoring replication fork progression during S phase of the cell cycle, and inhibition of CHK1 leads to stalling of replication forks and irreversible fork collapse (99101). Furthermore, CHK1 also influences many aspects of mitosis by controlling cyclin B/Cdk1 activation, contributing to spindle checkpoint function, chromosome segregation and cytokinesis (102104).

Tumor suppressor p53 plays an important role in cell cycle checkpoints. Following genotoxic stress, ATM/ATR/DNA-PKcs and CHK1/2 phosphorylate as well as stabilize p53. Subsequently, p53 drives a transcription program that includes p21waf1/cip1, which plays a pivotal role to initiate G1 and sustain G2 arrest (105, 106). Furthermore, p53 transcriptionally represses expression of cyclin B, CDC25B and polo-like kinase 1 (Plk1) that are required for mitotic entry (107109). p53 also participates in DNA repair and it is the main factor that determines the choice between DNA damage repair or the induction of senescence or apoptosis.


The cell cycle response to DNA damage is a highly efficient barrier against tumorigenesis. Premalignant cells have to overcome this barrier to progress into more malignant states (110, 111). Failure of mechanisms that regulate DNA damage checkpoint control leads to chromosomal aberrations (112) and genomic instability (113), both of which contribute to neoplastic transformation (114). Furthermore, alterations of proteins that control the DNA damage response-signaling pathway and impair the stringency of cell cycle checkpoints create a permissive environment that allows mutations to accumulate. The rapid accumulation of mutations in the genome of a cell leads to the so-called “mutator phenotype”, which contributes to tumor progression by creating tumor heterogeneity and subsequent emergence of aggressive types of cancer (115). The importance of an intact checkpoint related DDR mechanism is further underscored by the existence of hereditary cancer predisposition syndromes that are the result of a germ line mutation in a DDR gene, e.g., ataxia telangiectasia mutated (ATM), ataxia telangiectasia-like disorder (MRE11), Nijmegen breakage syndrome (NBS1), hereditary breast/ovarian cancer (BRCA1/2), Fanconi anemia (FA pathway genes) and Li-Fraumeni syndrome (TP53) (116). As mentioned previously, sporadic cancers have at least one defect in the DDR pathway, manifested as an altered cell cycle profile or sensitivity/resistance to genotoxic stress (7, 8), illustrating the importance of the DDR signaling in tumorigenesis.

Haploinsufficiency for a variety of DDR proteins, including ATM, ATR, γ-H2AX and CHK1 (117121) or knockdown/knockout of NBS1 (122, 123), RPA (124, 125), RAD17 (126), BRCA1 (127) and BRCA2 (128) is associated with genomic instability. Combined ATM and RAD9 (129) and ATM and HUS1 (130) haploinsufficiency led also to increased genomic instability. ATR and CHK1 participate in HR repair (131133), besides regulating the S and G2 checkpoints and replication initiation and fork stability (134139), thus facilitating repair of DNA breaks and preserving genomic integrity. CHK2 is an important mediator of cell cycle checkpoints, DNA repair and apoptosis. CHK2 is usually absent or downregulated in non-small cell lung cancer (140). Heterozygous mutations in ATR and CHK1 have been found in a subset of stomach, colon and endometrial cancers (141143). In animal studies, ATR and CHK1 hypomorphic mutations could contribute to increased risk of tumorigenesis (118, 144).

Other members of the DDR network, such as PLK1 (145), and Aurora kinases (146) are frequently overexpressed in human tumors and promote chromosomal instability through defects in the spindle assembly checkpoint that result in chromosome missegregation and centrosome amplification. In addition, cyclin-dependent kinases (CDK) are overactive in many tumors and a number of proteins that enhance or reduce CDK activation display oncogenic or tumor suppressive traits, respectively (147). CDC25 phosphatase (148), which is required for CDK activation, can act as an oncogene, whereas WEE1 that opposes the activation of CDK1 and enforces G2/M arrest after DNA damage acts as a tumor suppressor (149, 150). Moreover, dysregulation of cyclin E is considered a major factor of tumorigenesis. Elevated abundance of cyclin E is associated with various neoplasias (151) and its prolonged expression induces chromosomal instability (152). A number of CDK-specific inhibitors are currently being tested in clinical trials for the treatment of patients with a variety of cancers, such as multiple myeloma, pancreatic, and lung carcinomas (147).


Metastasis is the most clinically important attribute of cancer as more than 90% of cancer-related deaths are due to lack of local control. Tumor metastasis consists of a series of complex steps that need to be executed successfully to give rise to detectable tumors at sites distal to the organs where primary tumors initiate (153). Large-scale analyses of gene expression profiles of human cancers have revealed aberrant expression patterns of a number of genes involved in cell adhesion, migration, angiogenesis, kinase activation and other tumor-related functions. Although there is ample evidence that DNA repair genes are associated with the onset of tumorigenesis and DNA repair gene deficiencies cause inherent predisposition to cancer, a direct role of DNA repair or cell cycle checkpoint proteins in the etiology of metastasis has not been shown conclusively. Currently, the role of DNA repair genes in metastasis has only been inferred by DNA gene expression microarray analyses or by in vitro assays that serve as surrogates for in vivo metastasis phenotypes. Some of these genes are downregulated as tumors progress to a more malignant stage, while other genes are actually overexpressed and can affect the metastatic process. Whether these genes control the metastatic process due to their role in DNA repair or cell cycle control and the maintenance of genomic stability or because of some novel functions (e.g., acting as transcription factors or co-factors, or by more direct involvement for example in cell adhesion to matrix, etc.) is currently not known.

A genome-wide screen that compared gene expression in metastatic prostate and primary prostate tumors identified a strong correlation between high proliferation rates in metastatic cancers and overexpression of genes that participate in cell cycle regulation, DNA replication and DNA repair (49). Oncomine analyses showed that numerous human cancers, such as of the prostate, brain, cervix, head and neck, kidney, bladder and pancreas, displayed elevated levels of DNA repair proteins [for review see ref. (154)]. Moreover, in melanoma, there is considerable evidence that DNA repair genes are upregulated in metastases compared with primary tumors (57, 155). Gene expression microarray analyses as well as immunohistochemical examination of human melanoma specimens have shown an increase in expression of genes involved in HR and NER, but not BER (155). In contrast to the progression from melanocytes to primary melanoma, genetic stability appears to be necessary for a melanoma cell to give rise to distant metastasis (156). Therefore, the majority of neoplastic cells, found in primary melanomas poised to metastasize, have overexpressed genes responsible for efficient repair, ultimately resulting in genetically stable cells that are able to metastasize and grow at distant sites (155). Based on these results, it has been hypothesized that genomic instability is beneficial for the early stages of tumor development, whereas advanced and metastatic tumors overexpress an array of DNA repair genes to ensure a minimum of genomic stability (157). This inactivation–activation mode of DNA repair genes is not without precedent in other contexts (e.g., chemoresistance). It has been shown experimentally that a repair pathway may become inactivated early in carcinogenesis resulting in chromosomal instability, whereas consequent secondary mutations confer a selective advantage to the tumor. Subsequently, the repair pathway is reactivated (78). A case in point is the loss of the Fanconi anemia-BRCA pathway in cisplatin-sensitive ovarian cancer and re-gain of the pathway activity after prolonged treatment with cisplatin, which results in resistance to the drug (158).

A number of genes that participate in DNA damage induced checkpoints and DNA repair, and are either upregulated (e.g., RAD9, PARP1) or downregulated/mutated (e.g., BRCA1/2, ATM and TP53) have been associated with metastasis that was demonstrated using a variety of in vitro assays and by examining human tumor specimens by immunohistochemistry. A review of some of these genes and their potential relationship to metastasis follows.

RAD9 Activities

RAD9 can function as part of a heterotrimer with RAD1 and HUS1 (the RAD9-RAD1-HUS1 complex, 9-1-1), which is recruited to DNA damage sites by the RAD17-RFC (replication factor C) complex and is required for the subsequent activation of CHK1 and cell cycle arrest (159). However, RAD9 is a versatile protein that participates in numerous cell functions besides cell cycle checkpoint activation, such as DNA repair, telomere maintenance, dNTP biosynthesis, apoptosis and transcriptional regulation of genes (160). In addition, RAD9 can interact with several other proteins outside the context of the 9-1-1 complex and checkpoint functions (160).

Human RAD9 is involved in almost all aspects of DNA repair, including base excision repair (161, 162), nucleotide excision repair (163), mismatch repair (164) and homologous recombination, but not non-homologous end joining (165). Telomere instability and ionizing radiation sensitivity are linked to defective DNA repair (166) and RAD9 affects both. Moreover, chromosome end-to-end associations have been connected to genomic instability and carcinogenesis (167169). When RAD9 is inactivated, increases in chromosome end-to-end associations and frequency of telomere loss are observed (165). Studies in murine embryonic stem cells lacking Mrad9 (Mrad9–/– ES cells) demonstrate a marked increase in spontaneous chromosome aberrations (an increase in the frequency of chromosome and chromatid breaks) and HPRT (hypoxanthine phosphorybosyl transferase) mutations even in the absence of exposure to exogenous DNA damaging agents, indicating a role in the maintenance of genomic integrity (170).

RAD9 functions in apoptosis, in addition to its role in cell cycle checkpoint control and DNA damage repair pathways. Mrad9 deficiency causes midgestational embryonic death, accompanied by increased apoptosis and reduced cellular proliferation (170). The lack of Mrad9 in mouse ES cells also causes enhanced spontaneous apoptosis (171). RAD9 can interact and neutralize the action of anti-apoptotic Bcl-XL and Bcl-2 (172), and induce pro-apoptotic Bax activation (173). The pro-apoptotic action of RAD9 is potentiated by c-Abl phosphorylation (174) and protein kinase C delta (175), as well as the p63 transcription factor (176).

Another important and largely unexplored activity of RAD9 is its ability to function as a transcription factor and regulate a number of downstream target genes, most notably p21waf1/Cip1 (177). Human RAD9 has also been identified as a coregulator that can suppress androgen-androgen receptor transactivation in prostate cancer cell lines (178).

The Role of RAD9 in Metastasis

Reduction in RAD9 levels is associated with genomic instability manifested as telomere dysfunction, aberrant chromosomal segregation, high spontaneous levels of mutations, as well as defective DNA repair. Thus, given the roles of RAD9 in maintaining genomic stability, it is reasonable to hypothesize that the protein is important for tumorigenesis. Indeed, studies by a number of laboratories have linked aberrations in RAD9 abundance to a variety of cancers or an impact on phenotypes representing hallmark features characteristic of neoplastic transformation (160). Aberrant RAD9 expression has been associated with breast, lung, skin, thyroid and gastric cancers. RAD9 is frequently overexpressed in human prostate cancer tissue specimens as well as prostate cancer cell lines and, importantly, down-regulation of RAD9 in human tumor cell line xenografts impairs growth in nude mice, thus establishing a causative role for RAD9 in prostate cancer (179).

Cancer metastasis is a multi-step process in which tumor cells progressively acquire traits, including detachment from the extracellular matrix, anoikis resistance (defined as resistance to cell death triggered when cells lose adhesion to extracellular matrix), migration and invasion through the basement membrane, intravasation to blood and lymphatic vessels, extravasation from the circulation to distant sites, the ability to stimulate angiogenesis, and, finally, formation of macroscopic secondary malignant growths. At the molecular level, a number of signaling pathways, including those that involve integrins and Akt, contribute to the survival and progression of a tumor. Integrins are heterodimeric αβ transmembrane receptors that connect the extracellular matrix to the cytoskeleton and play important roles in migration, invasion and anoikis resistance. In particular, β1 integrin is known to confer higher survival and metastatic capacity to a number of cancer cells, including those of prostate origin (180, 181). The serine/threonine protein kinase Akt is a downstream effector of PI3K and an important regulator of various cellular functions, including cell metabolism, transcription, survival and proliferation. Activation of Akt, due to mutations of the phosphatidylinositol 3′ kinase (PI3K) p110 catalytic subunit or to loss of the phosphatase and tensin homolog (PTEN) tumor suppressor gene, occurs frequently in human cancers. The cancer cells rely heavily on active Akt to survive after experiencing a number of insults, such as genotoxic stress or growth factor depletion, and to regulate metastasis (182).

The first indication that RAD9 may be related to metastasis came from immunohistochemical analyses of human noncancer and cancer prostate specimens where the protein levels were positively correlated with more advanced stages of the disease (179). Furthermore, a number of in vitro metastasis markers such as cell motility, invasion, anoikis resistance and anchorage-independent growth, as well as activation of tumor promoting signaling pathways, specifically integrin expression and Akt activation were examined (183). Suppression of RAD9 protein abundance, by RNA interference, reduced both migration and invasion of DU145 as well as PC3 human prostate cancer cell lines, whereas ectopically expressing Mrad9, the mouse homolog of human RAD9, restored the phenotype in these cells (183). Likewise, anchorage-independent growth, which reflects most faithfully the in vivo metastatic potential of a cancer cell, was impaired when RAD9 was silenced in DU145 prostate cancer cells. Malignant cells have developed mechanisms to evade anoikis and either proliferate without matrix support or enter quiescence until a more suitable environment is presented. Anoikis resistance is, therefore, a prerequisite of tumor metastasis and is considered a hallmark of cancer. Akt kinase plays a pivotal role in the resistance of malignant cells to anoikis. RAD9 downregulation impaired Akt phosphorylation when prostate cancer DU145 and LNCaP cells were maintained in suspension. Conversely, when Mrad9 was ectopically expressed in DU145 with reduced levels of endogenous RAD9, Akt phosphorylation was restored, and cells became more resistant to anoikis (183). Silencing of RAD9 leads to a marked down-regulation of integrin β1. In addition, ectopic expression of Mrad9 restores integrin β1 levels when endogenous RAD9 expression is knocked down in DU145 cells. Furthermore, reduction of integrin β1 protein levels by a specific siRNA negated the effect of Mrad9 on migration and invasion, suggesting that RAD9 affects these metastasis-related processes through the activity of integrin β1 (183).

In addition to immunochemical data with human prostate specimens and the in vitro metastasis assays, gene expression profiling information for human prostate cancer also provides evidence of a role for RAD9 in tumor progression. Querying publically available datasets (184186) revealed that the relative RAD9 mRNA abundance in metastatic prostate tumors is twice as high as in primary prostate tumors (CGB and HBL, unpublished observations).

Given the function of RAD9 in tumorigenesis, it is reasonable to also consider whether other members of the 9-1-1 complex or RAD17 can impact the process. ATM/ATR-mediated phosphorylation of human RAD17, which recruits 9-1-1 to DNA damage sites, is required for claspin recruitment and CHK1 activation in response to genotoxic responses (187). However, a phosphorylation-defective RAD17 can neither recruit the 9-1-1 complex to the damage site, nor induce G2 checkpoint arrest in response to DNA damage (188). The potential association of RAD17 with cancer has been demonstrated in a number of studies. It has been shown that RAD17 acts as a haploinsufficient tumor suppressor that responds to oncogenic stress and loss of RAD17 is associated with poor prognosis in human B-cell lymphoma patients (189). Likewise, RAD17 is downregulated in head and neck squamous cell carcinomas (190). In contrast, elevated levels of RAD17 have been associated with breast (191) and lung carcinomas (192). Furthermore, immunohistochemical analyses have demonstrated that expression of human RAD17 might correlate with more advanced stages of non-small cell lung carcinoma (NSCLC). Abundance of RAD17 mRNA was correlated with lymph node metastasis, whereas RAD17 protein was highly prevalent at the advancing margin of the tumor of lung cancer tissue but not within the normal lung tissue (193).

Downregulation of HUS1 and RAD1 (as well as RAD9) lead to defects in DNA replication and cell cycle checkpoint control (194). HUS1 deficiency, for example, sensitizes mouse embryonic fibroblasts to etoposide-induced apoptosis (195), and HUS1 downregulation sensitizes human lung carcinoma cells to cisplatin (196). Similarly, HUS1 or RAD9 downregulation renders cells susceptible to ionizing radiation (197, 198). However, unlike RAD9, there is little information regarding the role of HUS1 and RAD1 in tumor initiation and/or progression. In one study, HUS1 levels correlated significantly with a number of adverse clinicopathologic factors in ovarian cancer, including stage, p53 and BAX expression, mitotic index, and apoptotic index (199). On the other hand, heterozygous deletion of mouse Mrad1 facilitates the development of experimental skin cancer in response to treatment with the carcinogen 7,12-dimethylbenzanthracene (DMBA) (200).


The PARP-1 protein is an abundant nuclear enzyme that modifies substrates by poly(ADP-ribose)ylation and is involved in the repair of single-strand breaks (116). In response to genotoxic insult, PARP-1 is recruited to sites of damage, where it becomes activated, and mediates the assembly as well as function of the base excision repair machinery (201). Distinct from its role in DNA repair, PARP-1 can act as a transcriptional regulator to control a diverse array of functions, including enhancer binding, association with insulators, modulation of chromatin structure, and/or transcription factor regulation (202). PARP-1 is overexpressed aberrantly in a number of human cancers, including those of breast and prostate (203, 204).

PARP-1 elicits pro-tumorigenic effects in androgen receptor-positive prostate cancer cells, in both the presence and absence of genotoxic drugs. Mechanistically, enzymatically active PARP-1 plays a critical role in the control of androgen receptor (AR) function. Moreover, in models of advanced prostate cancer, PARP-1 enzymatic activity is enhanced and regulates castration-resistant AR activity, further linking PARP-1 to AR activity and disease progression (205).

Recent evidence has uncovered a possible role of PARP-1 in metastasis. Chromosomal rearrangements involving genes encoding ETS transcription factors (ERG, ETV1) are found in 50% of human prostate cancer cases (206, 207). Translocations place the coding region or ERG or ETV1 under control of androgen-responsive promoters, such as TMPRSS2, thereby activating expression in response to androgens. At least in the case of ETS expressing cancers, the role of PARP-1 in metastasis appears to be due to its function as a transcription factor, although a role in DNA repair cannot be excluded (205, 208). ETS gene-mediated transcription and cell invasion require expression and activity of PARP-1 and DNA-PKcs, the kinase involved in NHEJ (204).

PARP-1 is also able to control SNAIL-1 transcription and Snail protein stability (208). Snail is a master regulator of the epithelial-mesenchymal transition (EMT) and has been implicated in key tumor biological processes, such as invasion and metastasis (209). PARP-1 is involved in the activation of SNAIL-1 gene transcription through binding to the integrin-linked kinase (ILK) promoter (210). PARP-1 downregulation has a clear effect on the EMT phenotype, with SNAIL-1 repression and E-cadherin upregulation, decreased cell elongation and invasiveness. Furthermore, PARP-1 and NF-kB together with Snail1 drive expression of the fibronectin gene, which is a typical mesenchymal gene (211). In contrast, PARP-1 has been shown in HaCaT keratinocyte cells to attenuate SMAD-mediated transcription and negatively regulate TGFβ-controlled genes involved in the EMT program, such as fibronectin (FN1) and N-cadherin (CDH2) (212).


The breast and ovarian cancer predisposition genes, BRCA1 and BRCA2, encode proteins that are required for efficient homologous recombination repair (213, 214). Germline mutations of BRCA1 predispose women to breast and ovarian cancers (70). Since its discovery, BRCA1 has been reported to be involved in multiple functions, all of which control genomic stability in the nucleus, such as cell cycle regulation and checkpoint activation, DNA repair (specifically HR), centrosome regulation, apoptosis and chromatin remodeling (215). BRCA1 also functions as a transcription regulatory cofactor (216).

Mutations in BRCA1 do not directly result in tumor formation, but instead cause genomic instability, subjecting cells to a high risk of malignant transformation (217). Furthermore, disruption of BRCA1 transcriptional activity can be crucial for tumor formation (218). Recent reports have identified novel roles of BRCA1 in the regulation of caveolin-1 (CAV-1) transcription and the inhibition of cell invasiveness (219), as well as the physical association with plasma membrane proteins ezrin-radixin-moesin, thus controlling cell spreading and motility, which have significant implications for tumor invasion and metastasis (220). Interestingly, the CAV-1 gene is upregulated in cells treated with ionizing radiation and its expression protects cells after exposure through modulating activities of both the HR and NHEJ pathways (221).

BRCA2 is considered a tumor suppressor gene involved in homologous recombination repair of DNA double-stranded breaks (222). In addition to its role in mediating DNA repair and genome stability, BRCA2 plays a role in the stabilization of stalled DNA replication forks, centrosome duplication, cytokinesis, and transcriptional regulation (214, 223225). BRCA2 can suppress tumor development by inhibiting cancer cell growth (226). Loss of BRCA2 triggers a proliferative response upon prostate cancer cell interaction with basement membrane proteins (227, 228). Besides its role in cell proliferation, BRCA2 functions in tumor progression as it can negatively impact on the metastatic potential of prostate cancer cells by down-regulating metalloprotease MMP-9 production through inhibition of PI3K/Akt, thus hindering cancer cell migration and invasion (229).

There is scant clinical information regarding the connection of BRCA1/2 mutations to the etiology of tumor metastasis. However, it has recently been shown that germline mutations in BRCA1/2 confer a more aggressive prostate cancer phenotype, with a higher probability of nodal involvement and distant metastasis (230).


Nijmegen breakage syndrome (NBS) is a chromosomal instability disorder associated with cancer predisposition, radiosensitivity, microcephaly and growth retardation (231). The gene defective in NBS is NBS1 (p95, nibrin) and is a member of the DNA double strand break repair complex that also includes MRE11 and RAD50 (232). NBS1 is a putative tumor suppressor gene as shown by the existence of mutations discovered in different tumors (233, 234). NBS1 is also a prostate cancer susceptibility gene (76). In line with a pro-tumorigenic activity, c-MYC oncogene directly activates NBS1 expression (235), and NBS1 overproduction stimulates PI3K activity and enhances cell transformation (236). The induction of tumorigenicity by NBS1 overexpression may proceed through activation of an oncogenic pathway or the repression of a tumor suppressor, whereas mutations of NBS1 could also contribute to tumorigenesis through deficiency in DNA repair leading to genomic instability (233, 234, 237).

Evidence that NBS1 may be associated with metastasis is: (1) NBS1 overexpression correlates with head and neck squamous cell carcinoma metastasis; (2) NBS1 overexpression induces EMT through the upregulation of Snail1 levels and matrix metalloprotease, MMP-2 and increases invasiveness/metastasis of head and neck cancer cells as observed both in vivo and in vitro (238); and (3) NBS1 upregulates heat shock proteins A4 and A14 with a concomitant increase in the in vitro migration, invasion and soft agar colony formation of the lung adenocarcinoma H1299 cell line (239). In addition, it has recently been demonstrated that although NBS1 haploinsufficiency leads to increased mammary tumor latency in the MMTV-neu mouse model, the tumors that do form are characterized by high metastatic potential (240), further highlighting the role of NBS1 in tumor metastasis.


A critical step in the formation of metastases is cell survival in the bloodstream. Normal and most cancer cells undergo programmed cell death (anoikis) when detached from their matrices, and metastatic cells must develop specific molecular strategies to survive or even proliferate in an anchorage-independent fashion before they localize to the metastatic site and extravasate. RAD51 is a DNA repair gene involved in tumorigenesis. Its downregulation has been associated with defects in error-free HR DNA repair. However, overexpression of RAD51, a rather common occurrence in human cancers (241), contributes to carcinogenesis as it is also associated with aberrant recombination between short repetitive elements and homologous sequences (241). Results with prostate cancer cell lines indicate that anchorage-independence sensitizes cells to genotoxic agents: however it also attenuates a faithful component of DNA repair by targeting the stability of RAD51. This temporal attenuation of HR may contribute to the accumulation of new mutations after DNA damage, which confer a selective advantage to the cells for survival under anchorage independent conditions (242).


The DNA repair protein known as X-ray complementing protein 3 (XRCC3), a member of the RAD51 family, participates in HR and is important for the maintenance of chromosome stability as well as DNA damage repair. XRCC3 affects the invasive behavior of MCF-7 and BT20 human breast cancer cell lines. Specifically, stable or transient overexpression of XRCC3 increased invasiveness in vitro (243). Moreover, XRCC3 overexpressing MCF-7 cells also showed a high frequency of tumorigenesis in vivo, and this phenotype was associated with increased activity of the metalloproteinase MMP-9 and the expression of known modulators of cell-cell adhesion and metastasis, such as CD44 (Receptor for hyaluronic acid), ID-1 (inhibitor of DNA binding 1), DDR1 (discoidin domain receptor tyrosine kinase 1), and TFF1 (trefoil factor 1). These findings suggest a role for XRCC3 in breast cancer cell line invasiveness and expression of genes associated with cell adhesion and invasion.


The ATM gene product is a serine/threonine protein kinase involved in cell cycle control, DNA repair and chromosomal stability. Its importance to cancer is underscored by the fact that inactivating mutations of ATM predispose individuals to the disease Ataxia Telangiectasia (244). Evidence that ATM may promote tumor progression and metastasis has come from recent studies revealing that ATM kinase is hyperactive in late stage breast tumors with lymph node metastasis (245). It was further demonstrated that ATM phosphorylates and stabilizes the epithelial-mesenchymal transition transcription factor SNAIL1, with a concomitant increase in cell migration and invasion in vitro and metastasis in vivo, which was reversed by inhibiting SNAIL phosphorylation by ATM (245). Likewise, inhibiting ATM kinase activity not only radiosensitizes human glioma cells, but it also impairs migration and invasion in vitro, possibly by reducing Akt and ERK activation (246). The stimulus that maintains high levels of ATM activation in advanced tumors is not known, but hypoxia or oxidative stress, which is able to promote metastasis and ATM activation, could be examples (247250).


The p53 protein is involved in DNA damage repair and cell cycle checkpoint control (251). It plays critical roles in maintaining genetic stability, and TP53 is the most commonly mutated tumor suppressor gene in human cancers (251). Mutations of TP53 are mainly seen in later tumor stages and coincide with more aggressive types of cancer (252254). Interestingly, the majority of TP53 alterations are missense mutations within the DNA binding domain, thus maintaining a full-length protein that has lost its tumor suppressor function (255). However, in addition to losing this function, many mutant p53 proteins also acquire novel, oncogenic activities (256). These gain-of-function p53 mutants lead to increased genomic instability by interfering with proper ATM activation and DNA repair (257, 258). This causes increased incidence of chromosomal translocations (259) and chymothripsis (260), as well as gene amplifications (261). Aneuploidy is promoted by inhibiting assembly of the mitotic spindle checkpoint, as well as inducing centrosome amplification (256). This can inhibit apoptosis by, among other mechanisms, suppressing the function of p73 that induces p53-independent apoptosis after DNA damage (262). p53 inhibits tumor metastasis by multiple mechanisms. For example, p53 controls the transcription of SMAR1 (scaffold/matrix attachment region binding protein 1), which in turn controls cyclin D1 (CCND1) gene expression and inhibits migration as well as invasion by interfering with TGFβ signaling in breast cancer (263). Not surprisingly, breast tumors in advanced stages show reduced expression of SMAR1 (263). In contrast, mutant p53 protein can promote aspects of the metastatic process (264), such as migration and invasion, epithelial to mesenchymal transition, or through the inhibition of p63 protein, which results in increased trafficking of β1 integrin (265), an integrin that is intimately involved in metastasis in human breast and prostate carcinomas (266268). The increased rate of recycling of this integrin to the cell plasma membrane correlates positively with cell migration and invasion (269).


The growth arrest and DNA damage gene, GADD45a, plays important roles in the control of cell cycle checkpoints, DNA repair (270) and apoptosis (271). Mouse embryonic fibroblasts derived from GADD45a-null mice exhibit genomic instability, single oncogene-mediated transformation, loss of normal cellular senescence, increased cellular proliferation, centrosome amplification and reduced DNA repair. A high frequency of GADD45a point mutations has been identified in human pancreatic cancer (272), whereas increased gene methylation and decreased protein levels have been shown in breast cancer (273).

A role for GADD45a in metastasis is inferred by the observations that it is involved in the control of cell contact inhibition and cell-cell adhesion by enhancing β-catenin protein stability and translocation to the cell membrane (274). Furthermore, GADD45a inhibits cell migration and invasion by altering expression of various genes encoding extracellular matrix, cell communication, and cell adhesion proteins (275).


The gene NM23 functions in DNA repair and determining whether metastases will form (276). Unlike the other examples where established DNA repair genes are examined for their role in metastasis, NM23 was first established as an antimetastatic gene, and its significance as a metastasis suppressor has been highlighted in numerous studies (276). Low NM23 expression in primary melanomas is correlated with poor clinical outcome, suggesting relevance of NM23 deficiency to initiation and/or progression in earlier stages of this tumor (277). Subsequent studies revealed that NM23 participates in DNA repair as well. Importantly, the protein's DNA repair activity is required for its metastasis suppressing function, albeit the exact mechanism remains elusive (278). Recent findings have shown that NM23-H1 (isoform H1) participates in nucleotide excision repair (279), however, it is not known whether this function is required for the antimetastatic role.

Other DDR Proteins

A number of other DDR proteins, such as MCPH1, 14-3-3σ, CDC25A, TIP60 and H2AX, have been associated with tumor metastasis. Evidence is mainly based on immunohistochemical analyses of clinical specimens or in vitro studies.

MCPH1 (microcephalin 1, also known as BRIT1), a repressor of human telomerase reverse transcriptase (hTERT) function and a key regulator in the DDR pathway, ensures genomic stability and acts as a barrier to the development of cancer (280). MCPH1 level is inversely correlated with the likelihood of breast cancer metastasis (281) or prostate cancer (282). Likewise, inactivation of the G2/M checkpoint protein 14-3-3σ correlates with lymph node metastasis in nasopharyngeal carcinoma (283). The axis PLK1-CDC25A that permits cells to enter mitosis is often dysregulated in metastatic hepatocellular carcinoma, and cisplatin treatment of metastatic cells does not lead to CDC25A degradation or PLK1 inactivation as normally happens after DNA damage is incurred. As a result, cells enter mitosis, but without mitotic catastrophe, thus leading to increased genetic instability (284). On the other hand, nonmetastatic cells responded to cisplatin with the degradation of CDC25A and the downregulation of PLK1 activity (284).

The tumor suppressor TIP60 is a protein lysine acetytransferase involved in DNA damage response and repair particularly of double-strand breaks (285), by acetylating and activating, among other substrates, ATM (286). The TIP60 gene is frequently downregulated in colon and lung carcinomas (287). Moreover, downregulation of TIP60 correlates with distant metastasis in colon cancer (288), as well as melanoma (289). In the latter case, ectopic expression of Tip60 in melanoma cells reduced and knockdown increased in vitro cell migration, pointing further to a potential role of Tip60 in metastasis (289).

Histone H2AX is an important effector of the DNA damage response that is responsible for recruiting cell cycle checkpoint and DNA repair factors to sites of double-strand breaks (290). By facilitating the DNA damage response and repair, H2AX functions as a tumor suppressor. H2AX maps to chromosome 11q23, a region that is deleted or mutated in a variety of human malignancies, including leukemia, breast and head and neck cancers (290). However, H2AX can also promote tumor growth and pathologic angiogenesis under conditions of hypoxia (291) and therefore aid the dissemination of tumor cells to metastasize to distant sites. H2AX is needed for endothelial cell proliferation under hypoxic conditions and for hypoxia-driven neovascularization, whereas genetic ablation of H2AX reduces the proliferation of these cells in vitro and in vivo (291). However, it is still not clear whether the DNA repair function of H2AX is required for the regulation of endothelial cell proliferation under hypoxia conditions (292).


In recent years, it has become apparent that many genes classically thought to operate in DNA repair or checkpoint control also have roles in carcinogenesis and in particular tumor metastasis as well. However, the molecular mechanisms involved are not completely understood. Most published experiments are correlative in nature, and therefore, at present, cause-effect relationships between most of these genes and cancer metastasis cannot be unambiguously assigned. The evidence that DNA repair or checkpoint genes participate in metastasis comes mainly from genome profiling data of primary versus metastatic tumors, or from immunohistochemical analyses of patient tumor specimens. In addition, in vitro data have linked expression of some of these genes to increased migration and invasion, anoikis resistance and anchorage-independent growth. Molecularly, DNA repair or cell cycle checkpoint genes affect pro-tumorigenic and pro-metastatic pathways involving Akt activation, integrin expression, as well as transcriptional control of genes involved in epithelial-to-mesenchymal transition and metalloproteases. It is therefore necessary to prove that the encoded proteins drive metastasis in animal models to demonstrate directly a cause-effect relationship. So far, this has been shown only for NBS1 in head and neck cancer cell lines by an in vivo tail vein metastasis assay (238).

Proteins that participate in DNA repair or cell cycle checkpoint control usually have multiple cellular, biochemical or molecular functions, as shown schematically in Fig. 1 and detailed in Tables I and II. An emerging common theme for many DNA repair proteins is that they can function in gene regulation as transcriptional factors or cofactors. RAD9, for example, can function as a sequence specific transcription factor and regulate a number of genes including p21waf1/Cip1 (177), whereas BRCA1, which lacks sequence specific DNA binding, can be recruited to promoters by sequence specific transcription factors and act as a transcriptional co-activator or co-repressor (216). Likewise, GADD45a alters global transcript abundance, affecting proteins important for cell migration and invasion, such as those impacting on cell–cell adhesion (275).

Which of the multiple functions of DNA repair or cell cycle checkpoint control proteins is actually required for regulating metastases is not clear. One can speculate that DNA repair activity is required. On the other hand, the transcriptional regulatory activity of numerous DNA repair proteins will certainly be important. It is already known that DNA repair proteins control, at the transcriptional level, the abundance of many other proteins involved in metastatic pathways and certainly more will be discovered as studies progress. Finally, specific protein–protein interactions of DNA repair or checkpoint factors with as yet unidentified proteins will also likely influence metastasis. A very complex picture is emerging from all of these investigations. Nevertheless, from a pragmatic perspective, resolution of the molecular mechanisms involved is important to facilitate the design of therapies that target DNA repair and cell cycle checkpoint proteins as novel anti-cancer agents.


This work was supported, in whole or part, by National Institutes of Health grants R01CA130536, R01GM079107 and P01CA49062 (HBL).


  1. NJ Curtin DNA repair dysregulation from cancer driver to therapeutic target. Nat Rev Cancer 2012; 12:801–17. Google Scholar
  2. 2
  3. J de Boer JH Hoeijmakers Nucleotide excision repair and human syndromes. Carcinogenesis 2000; 21:453–60. Google Scholar
  4. 3
  5. AK Rustgi The genetics of hereditary colon cancer. Genes Dev 2007; 21:2525–38. Google Scholar
  6. 4
  7. D Moshous C Pannetier RD Chasseval FL Deist M Cavazzana-Calvo S Romana et. al . Partial T and B lymphocyte immunodeficiency and predisposition to lymphoma in patients with hypomorphic mutations in Artemis. J Clin Invest 2003; 111:381–7. Google Scholar
  8. 5
  9. PL Roddam S Rollinson M O'Driscoll PA Jeggo A Jack GJ Morgan Genetic variants of NHEJ DNA ligase IV can affect the risk of developing multiple myeloma, a tumour characterised by aberrant class switch recombination. J Med Genet 2002; 39:900–5. Google Scholar
  10. 6
  11. ML Li RA Greenberg Links between genome integrity and BRCA1 tumor suppression. Trends Biochem Sci 2012; 37:418–24. Google Scholar
  12. 7
  13. T Helleday E Petermann C Lundin B Hodgson RA Sharma DNA repair pathways as targets for cancer therapy. Nat Rev Cancer 2008; 8:193–204. Google Scholar
  14. 8
  15. HB Lieberman DNA damage repair and response proteins as targets for cancer therapy. Curr Med Chem 2008; 15:360–7. Google Scholar
  16. 9
  17. P Hasty J Campisi J Hoeijmakers H van Steeg J Vijg Aging and genome maintenance: lessons from the mouse? Science 2003; 299:1355–9. Google Scholar
  18. 10
  19. LH Thompson D Schild Recombinational DNA repair and human disease. Mutat Res 2002; 509:49–78. Google Scholar
  20. 11
  21. C Lahtz GP Pfeifer Epigenetic changes of DNA repair genes in cancer. J Mol Cell Biol 2011; 3:51–8. Google Scholar
  22. 12
  23. M Toyota H Suzuki Epigenetic drivers of genetic alterations. Adv Genet 2010; 70:309–23. Google Scholar
  24. 13
  25. M Esteller SR Hamilton PC Burger SB Baylin JG Herman Inactivation of the DNA repair gene O6-methylguanine-DNA methyltransferase by promoter hypermethylation is a common event in primary human neoplasia. Cancer Res 1999; 59:793–7. Google Scholar
  26. 14
  27. M Esteller J Garcia-Foncillas E Andion SN Goodman OF Hidalgo V Vanaclocha et al . Inactivation of the DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents. N Engl J Med 2000; 343:1350–4. Google Scholar
  28. 15
  29. M Mellai V Caldera L Annovazzi A Chiò M Lanotte P Cassoni et al . MGMT promoter hypermethylation in a series of 104 glioblastomas. Cancer Genomics Proteomics 2009; 6:219–27. Google Scholar
  30. 16
  31. J Shamsara S Sharif S Afsharnezhad M Lotfi HR Raziee K Ghaffarzadegan et al . Association between MGMT promoter hypermethylation and p53 mutation in glioblastoma. Cancer Invest 2009; 27:825–9. Google Scholar
  32. 17
  33. KK Herfarth TP Brent RP Danam JS Remack IJ Kodner SA Wells et al . A specific CpG methylation pattern of the MGMT promoter region associated with reduced MGMT expression in primary colorectal cancers. Mol Carcinog 1999; 24:90–8. Google Scholar
  34. 18
  35. S Ogino A Hazra GJ Tranah GJ Kirkner T Kawasaki K Nosho et al . MGMT germline polymorphism is associated with somatic MGMT promoter methylation and gene silencing in colorectal cancer. Carcinogenesis 2007; 28:1985–90. Google Scholar
  36. 19
  37. P Wolf YC Hu K Doffek D Sidransky SA Ahrendt O(6)-Methylguanine-DNA methyltransferase promoter hypermethylation shifts the p53 mutational spectrum in non-small cell lung cancer. Cancer Res 2001; 61:8113–7. Google Scholar
  38. 20
  39. JY Wu J Wang JC Lai YW Cheng KT Yeh TC Wu et al . Association of O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation with p53 mutation occurrence in non-small cell lung cancer with different histology, gender, and smoking status. Ann Surg Oncol 2008; 15:3272–7. Google Scholar
  40. 21
  41. N Oue H Shigeishi H Kuniyasu H Yokozaki K Kuraoka et al . Promoter hypermethylation of MGMT is associated with protein loss in gastric carcinoma. Int J Cancer 2001; 93:805–9. Google Scholar
  42. 22
  43. D Goldenberg S Harden BG Masayesva P Ha N Benoit WH Westra et al . Intraoperative molecular margin analysis in head and neck cancer. Arch Otolaryngol Head Neck Surg 2004; 130:39–44. Google Scholar
  44. 23
  45. S Maruya JP Issa RS Weber DI Rosenthal JC Haviland R Lotan et al . Differential methylation status of tumor-associated genes in head and neck squamous carcinoma: incidence and potential implications. Clin Cancer Res 2004; 10:3825–30. Google Scholar
  46. 24
  47. K Steinmann A Sandner U Schagdarsurengin RH Dammann Frequent promoter hypermethylation of tumor-related genes in head and neck squamous cell carcinoma. Oncol Rep 2009; 22:1519–26. Google Scholar
  48. 25
  49. M Esteller M Toyota M Sanchez-Cespedes G Capella MA Peinado DN Watkins et al . Inactivation of the DNA repair gene O6-methylguanine-DNA methyltransferase by promoter hypermethylation is associated with G to A mutations in K-ras in colorectal tumorigenesis. Cancer Res 2000; 60:2368–71. Google Scholar
  50. 26
  51. M Esteller RA Risques M Toyota G Capella V Moreno MA Peinado et al . Promoter hypermethylation of the DNA repair gene O(6)-methylguanine-DNA methyltransferase is associated with the presence of G:C to A:T transition mutations in p53 in human colorectal tumorigenesis. Cancer Res 2001; 61:4689–92. Google Scholar
  52. 27
  53. GL Dianov U Hübscher Mammalian base excision repair: the forgotten archangel. Nucleic Acids Res 2013; 41:3483–90. Google Scholar
  54. 28
  55. DM Wilson 3rd D Kim BR Berquist AJ Sigurdson Variation in base excision repair capacity. Mutat Res 2011; 711:100–12. Google Scholar
  56. 29
  57. MM Slupska C Baikalov WM Luther JH Chiang YF Wei JH Miller Cloning and sequencing a human homolog (hMYH) of the Escherichia coli mutY gene whose function is required for the repair of oxidative DNA damage. J Bacteriol 1996; 178:3885–92. Google Scholar
  58. 30
  59. N Al-Tassan NH Chmiel J Maynard N Fleming AL Livingston GT Williams et al . Inherited variants of MYH associated with somatic G:C–>T:A mutations in colorectal tumors. Nat Genet 2002; 30:227–32. Google Scholar
  60. 31
  61. S Jones P Emmerson J Maynard JM Best S Jordan GT Williams et al . Biallelic germline mutations in MYH predispose to multiple colorectal adenoma and somatic G:C–>T:A mutations. Hum Mol Genet 2002; 11:2961–7. Google Scholar
  62. 32
  63. K Arai K Morishita K Shinmura T Kohno SR Kim T Nohmi et al . Cloning of a human homolog of the yeast OGG1 gene that is involved in the repair of oxidative DNA damage. Oncogene 1997; 14:2857–61. Google Scholar
  64. 33
  65. S Chevillard JP Radicella C Levalois J Lebeau MF Poupon S Oudard et al . Mutations in OGG1, a gene involved in the repair of oxidative DNA damage, are found in human lung and kidney tumours. Oncogene 1998; 16:3083–6. Google Scholar
  66. 34
  67. K Shinmura J Yokota The OGG1 gene encodes a repair enzyme for oxidatively damaged DNA and is involved in human carcinogenesis. Antioxid Redox Signal 2001; 3:597–609. Google Scholar
  68. 35
  69. B Peng EM Hurt DR Hodge SB Thomas WL Farrar DNA hypermethylation and partial gene silencing of human thymine- DNA glycosylase in multiple myeloma cell lines. Epigenetics 2006; 1:138–45. Google Scholar
  70. 36
  71. KA Robertson HA Bullock Y Xu R Tritt E Zimmerman TM Ulbright et al . Altered expression of Ape1/ref-1 in germ cell tumors and overexpression in NT2 cells confers resistance to bleomycin and radiation. Cancer Res 2001; 61:2220–5. Google Scholar
  72. 37
  73. JR Silber MS Bobola A Blank KD Schoeler PD Haroldson MB Huynh et al . The apurinic/apyrimidinic endonuclease activity of Ape1/Ref-1 contributes to human glioma cell resistance to alkylating agents and is elevated by oxidative stress. Clin Cancer Res 2002; 8:3008–18. Google Scholar
  74. 38
  75. MR Albertella A Lau MJ O'Connor The overexpression of specialized DNA polymerases in cancer. DNA Repair (Amst) 2005; 4:583–93. Google Scholar
  76. 39
  77. DK Srivastava I Husain CL Arteaga SH Wilson DNA polymerase beta expression differences in selected human tumors and cell lines. Carcinogenesis 1999; 20:1049–54. Google Scholar
  78. 40
  79. Y Canitrot C Cazaux M Fréchet K Bouayadi C Lesca B Salles et al . Overexpression of DNA polymerase beta in cell results in a mutator phenotype and a decreased sensitivity to anticancer drugs. Proc Natl Acad Sci U S A 1998; 95:12586–90. Google Scholar
  80. 41
  81. SS Wallace DL Murphy JB Sweasy Base excision repair and cancer. Cancer Lett 2012; 327:73–89. Google Scholar
  82. 42
  83. D Starcevic S Dalal JB Sweasy Is there a link between DNA polymerase beta and cancer? Cell Cycle 2004; 3:998–1001. Google Scholar
  84. 43
  85. LR Hiraoka JJ Harrington DS Gerhard MR Lieber CL Hsieh Sequence of human FEN-1, a structure-specific endonuclease, and chromosomal localization of the gene (FEN1) in mouse and human. Genomics 199; 25:220–5. Google Scholar
  86. 44
  87. X Wu TE Wilson MR Lieber A role for FEN-1 in nonhomologous DNA end joining: the order of strand annealing and nucleolytic processing events. Proc Natl Acad Sci U S A 1999; 96:1303–8. Google Scholar
  88. 45
  89. K Kikuchi Y Taniguchi A Hatanaka E Sonoda H Hochegger N Adachi et al . Fen-1 facilitates homologous recombination by removing divergent sequences at DNA break ends. Mol Cell Biol 2005; 25:6948–55. Google Scholar
  90. 46
  91. P Singh L Zheng V Chavez J Qiu B Shen Concerted action of exonuclease and Gap-dependent endonuclease activities of FEN-1 contributes to the resolution of triplet repeat sequences (CTG)n- and (GAA)n-derived secondary structures formed during maturation of Okazaki fragments. J Biol Chem 2007; 282:3465–77. Google Scholar
  92. 47
  93. T Nikolova M Christmann B Kaina FEN1 is overexpressed in testis, lung and brain tumors. Anticancer Res 2009; 29:2453–9. Google Scholar
  94. 48
  95. JS Lam DB Seligson H Yu A Li M Eeva AJ Pantuck et al . Flap endonuclease 1 is overexpressed in prostate cancer and is associated with a high Gleason score. BJU Int 2006; 98:445–51. Google Scholar
  96. 49
  97. E LaTulippe J Satagopan A Smith H Scher P Scardino V Reuter et al . Comprehensive gene expression analysis of prostate cancer reveals distinct transcriptional programs associated with metastatic disease. Cancer Res 2002; 62:4499–506. Google Scholar
  98. 50
  99. A Krause V Combaret I Iacono B Lacroix C Compagnon C Bergeron et al . Genome-wide analysis of gene expression in neuroblastomas detected by mass screening. Cancer Lett 2005; 225:111–20. Google Scholar
  100. 51
  101. CA Iacobuzio-Donahue A Maitra M Olsen AW Lowe NT van Heek C Rosty et al . Exploration of global gene expression patterns in pancreatic adenocarcinoma using cDNA microarrays. Am J Pathol 2003; 162:1151–62. Google Scholar
  102. 52
  103. P Singh M Yang H Dai D Yu Q Huang W Tan et al . Overexpression and hypomethylation of flap endonuclease 1 gene in breast and other cancers. Mol Cancer Res 2008; 6:1710–7. Google Scholar
  104. 53
  105. M Nitta D Kozono R Kennedy J Stommel K Ng PO Zinn et al . Targeting EGFR induced oxidative stress by PARP1 inhibition in glioblastoma therapy. PLoS One 2010; 5(5):e10767. Google Scholar
  106. 54
  107. K Sugasawa Regulation of damage recognition in mammalian global genomic nucleotide excision repair. Mutat Res 2010; 685:29–37. Google Scholar
  108. 55
  109. I Kamileri I Karakasilioti GA Garinis Nucleotide excision repair: new tricks with old bricks Trends Genet 2012; 28:566–73. Google Scholar
  110. 56
  111. N Zeng-Rong J Paterson L Alpert MS Tsao J Viallet MA Alaoui-Jamali Elevated DNA repair capacity is associated with intrinsic resistance of lung cancer to chemotherapy. Cancer Res 1995; 55:4760–4. Google Scholar
  112. 57
  113. Q Wei L Cheng K Xie CD Bucana Z Dong Direct correlation between DNA repair capacity and metastatic potential of K-1735 murine melanoma cells. J Invest Dermatol 1997; 108:3–6. Google Scholar
  114. 58
  115. B Köberle JR Masters JA Hartley RD Wood Defective repair of cisplatin-induced DNA damage caused by reduced XPA protein in testicular germ cell tumours. Curr Biol 1999; 9:273–6. Google Scholar
  116. 59
  117. J Yang Z Xu J Li R Zhang G Zhang H Ji et al . XPC epigenetic silence coupled with p53 alteration has a significant impact on bladder cancer outcome. J Urol 2010; 184:336–43. Google Scholar
  118. 60
  119. HY Chen CJ Shao FR Chen AL Kwan ZP Chen Role of ERCC1 promoter hypermethylation in drug resistance to cisplatin in human gliomas. Int J Cancer 2010; 126:1944–54. Google Scholar
  120. 61
  121. C Kiyohara K Yoshimasu Genetic polymorphisms in the nucleotide excision repair pathway and lung cancer risk: a meta-analysis. Int J Med Sci 2007; 4:59–71. Google Scholar
  122. 62
  123. SA Martin CJ Lord A Ashworth Therapeutic targeting of the DNA mismatch repair pathway. Clin Cancer Res 2010; 16:5107–13. Google Scholar
  124. 63
  125. M Pineda S González C Lázaro I Blanco G Capellá Detection of genetic alterations in hereditary colorectal cancer screening. Mutat Res 2010; 693:19–31. Google Scholar
  126. 64
  127. JM Cunningham CY Kim ER Christensen DJ Tester Y Parc LJ Burgart et al . The frequency of hereditary defective mismatch repair in a prospective series of unselected colorectal carcinomas. Am J Hum Genet 2001; 69:780–90. Google Scholar
  128. 65
  129. MF Kane M Loda GM Gaida J Lipman R Mishra H Goldman et al . Methylation of the hMLH1 promoter correlates with lack of expression of hMLH1 in sporadic colon tumors and mismatch repair-defective human tumor cell lines. Cancer Res 1997; 57:808–11. Google Scholar
  130. 66
  131. JG Herman A Umar K Polyak JR Graff N Ahuja JP Issa et al . Incidence and functional consequences of hMLH1 promoter hypermethylation in colorectal carcinoma. Proc Natl Acad Sci U S A 1998; 95:6870–5. Google Scholar
  132. 67
  133. M Esteller R Levine SB Baylin LH Ellenson JG Herman MLH1 promoter hypermethylation is associated with the microsatellite instability phenotype in sporadic endometrial carcinomas. Oncogene 1998; 17:2413–7. Google Scholar
  134. 68
  135. AS Fleisher M Esteller S Wang G Tamura H Suzuki J Yin et al . Hypermethylation of the hMLH1 gene promoter in human gastric cancers with microsatellite instability. Cancer Res 1999; 59:1090–5. Google Scholar
  136. 69
  137. J Chen DP Silver D Walpita SB Cantor AF Gazdar G Tomlinson et al . Stable interaction between the products of the BRCA1 and BRCA2 tumor suppressor genes in mitotic and meiotic cells. Mol Cell 1998; 2:317–28. Google Scholar
  138. 70
  139. PL Welcsh MC King BRCA1 and BRCA2 and the genetics of breast and ovarian cancer. Hum Mol Genet 2001; 10:705–13. Google Scholar
  140. 71
  141. D Li E Kumaraswamy LM Harlan-Williams RA Jensen The role of BRCA1 and BRCA2 in prostate cancer. Front Biosci 2013; 18:1445–59. Google Scholar
  142. 72
  143. J Iqbal A Ragone J Lubinski HT Lynch P Moller P Ghadirian et al . The incidence of pancreatic cancer in BRCA1 and BRCA2 mutation carriers. Br J Cancer 2012; 107:2005–9. Google Scholar
  144. 73
  145. M Esteller JM Silva G Dominguez F Bonilla X Matias-Guiu E Lerma et al . Promoter hypermethylation and BRCA1 inactivation in sporadic breast and ovarian tumors. J Natl Cancer Inst 2000; 92:564–9. Google Scholar
  146. 74
  147. A Ciccia SJ Elledge The DNA damage response: making it safe to play with knives. Mol Cell 2010; 40:179–204. Google Scholar
  148. 75
  149. R Varon A Reis G Henze HG von Einsiedel K Sperling K Seeger Mutations in the Nijmegen Breakage Syndrome gene (NBS1) in childhood acute lymphoblastic leukemia (ALL). Cancer Res 2001; 61:3570–2. Google Scholar
  150. 76
  151. C Cybulski B Górski T Debniak B Gliniewicz M Mierzejewski B Masojć et al . NBS1 is a prostate cancer susceptibility gene. Cancer Res 2004; 64:1215–9. Google Scholar
  152. 77
  153. NG Kim YR Choi MJ Baek YH Kim H Kang NK Kim et al . Frameshift mutations at coding mononucleotide repeats of the hRAD50 gene in gastrointestinal carcinomas with microsatellite instability. Cancer Res 2001; 61:36–8. Google Scholar
  154. 78
  155. RD Kennedy AD D'Andrea DNA repair pathways in clinical practice: lessons from pediatric cancer susceptibility syndromes J Clin Oncol 2006; 24:3799–808. Google Scholar
  156. 79
  157. CR Wilson SE Davidson GP Margison SP Jackson JH Hendry CM West Expression of Ku70 correlates with survival in carcinoma of the cervix. Br J Cancer 2000; 83:1702–6. Google Scholar
  158. 80
  159. Y Komuro T Watanabe Y Hosoi Y Matsumoto K Nakagawa N Tsuno et al . The expression pattern of Ku correlates with tumor radiosensitivity and disease free survival in patients with rectal carcinoma. Cancer 2002; 95:1199–205. Google Scholar
  160. 81
  161. B Rigas S Borgo A Elhosseiny V Balatsos Z Manika H Shinya et al . Decreased expression of DNA-dependent protein kinase, a DNA repair protein, during human colon carcinogenesis. Cancer Res 2001; 61:8381–4. Google Scholar
  162. 82
  163. J Yang Z Chen Y Liu RJ Hickey LH Malkas Altered DNA polymerase iota expression in breast cancer cells leads to a reduction in DNA replication fidelity and a higher rate of mutagenesis. Cancer Res 2004; 64:5597–607. Google Scholar
  164. 83
  165. J O-Wang K Kawamura Y Tada H Ohmori H Kimura S Sakiyama et al . DNA polymerase kappa, implicated in spontaneous and DNA damage-induced mutagenesis, is overexpressed in lung cancer. Cancer Res 2001; 61:5366–9. Google Scholar
  166. 84
  167. F Boudsocq P Benaim Y Canitrot M Knibiehler F Ausseil JP Capp et al . Modulation of cellular response to cisplatin by a novel inhibitor of DNA polymerase beta. Mol Pharmacol 2005; 67:1485–92. Google Scholar
  168. 85
  169. J Falck J Coates SP Jackson Conserved modes of recruitment of ATM, ATR and DNA-PKcs to sites of DNA damage. Nature 2005; 434:605–11. Google Scholar
  170. 86
  171. M Stucki JA Clapperton D Mohammad MB Yaffe SJ Smerdon SP Jackson MDC1 directly binds phosphorylated histone H2AX to regulate cellular responses to DNA double-strand breaks. Cell 2005; 123:1213–26. Google Scholar
  172. 87
  173. S Bekker-Jensen N Mailand Assembly and function of DNA double-strand break repair foci in mammalian cells. DNA Repair (Amst) 2010; 9:1219–28. Google Scholar
  174. 88
  175. L Zou SJ Elledge Sensing DNA damage through ATRIP recognition of RPA-ssDNA complexes. Science 2003; 300:1542–8. Google Scholar
  176. 89
  177. S Delacroix JM Wagner M Kobayashi K Yamamoto LM Karnitz The Rad9-Hus1-Rad1 (9-1-1) clamp activates checkpoint signaling via TopBP1. Genes Dev 2007; 21:1472–7. Google Scholar
  178. 90
  179. C Cotta-Ramusino ER McDonald 3rd K Hurov ME Sowa JW Harper SJ. A Elledge DNA damage response screen identifies RHINO, a 9-1-1 and TopBP1 interacting protein required for ATR signaling. Science 2011; 332:1313–7. Google Scholar
  180. 91
  181. VA Smits PM Reaper SP Jackson Rapid PIKK-dependent release of CHK1 from chromatin promotes the DNA-damage checkpoint response. Curr Biol 2006; 16:150–9. Google Scholar
  182. 92
  183. N Mailand J Falck C Lukas RG Syljuâsen M Welcker J Bartek et al . Rapid destruction of human CDC25A in response to DNA damage. Science 2000; 288:1425–9. Google Scholar
  184. 93
  185. J Jin T Shirogane L Xu G Nalepa J Qin SJ Elledge et al . SCFbeta-TRCP links CHK1 signaling to degradation of the CDC25A protein phosphatase. Genes Dev 2003; 17:3062–74. Google Scholar
  186. 94
  187. M Melixetian DK Klein CS Sørensen K Helin NEK11 regulates CDC25A degradation and the IR-induced G2/M checkpoint. Nat Cell Biol 2009; 11:1247–53. Google Scholar
  188. 95
  189. H Jiang HC Reinhardt J Bartkova J Tommiska C Blomqvist H Nevanlinna et al . The combined status of ATM and p53 link tumor development with therapeutic response. Genes Dev 2009; 23:1895–909. Google Scholar
  190. 96
  191. R Agami R Bernards Distinct initiation and maintenance mechanisms cooperate to induce G1 cell cycle arrest in response to DNA damage. Cell 2000; 102:55–66. Google Scholar
  192. 97
  193. F Takahashi-Yanaga T Sasaguri GSK-3beta regulates cyclin D1 expression: a new target for chemotherapy. Cell Signal 2008; 20:581–9. Google Scholar
  194. 98
  195. MK Santra N Wajapeyee MR Green F-box protein FBXO31 mediates cyclin D1 degradation to induce G1 arrest after DNA damage. Nature 2009; 459:722–5. Google Scholar
  196. 99
  197. H Takai K Tominaga N Motoyama YA Minamishima H Nagahama T Tsukiyama et al . Aberrant cell cycle checkpoint function and early embryonic death in CHK1(-/-) mice. Genes Dev 2000; 14:1439–47. Google Scholar
  198. 100
  199. RG Syljuåsen CS Sørensen LT Hansen K Fugger C Lundin F Johansson et al . Inhibition of human CHK1 causes increased initiation of DNA replication, phosphorylation of ATR targets, and DNA breakage. Mol Cell Biol 2005; 25:3553–62. Google Scholar
  200. 101
  201. A Maya-Mendoza E Petermann DA Gillespie KW Caldecott DA Jackson CHK1 regulates the density of active replication origins during the vertebrate S phase. EMBO J 2007; 26:2719–31. Google Scholar
  202. 102
  203. A Krämer N Mailand C Lukas RG Syljuåsen CJ Wilkinson EA Nigg et al . Centrosome-associated CHK1 prevents premature activation of cyclin-B-Cdk1 kinase. Nat Cell Biol 2004; 6:884–91. Google Scholar
  204. 103
  205. G Zachos EJ Black M Walker MT Scott P Vagnarelli WC Earnshaw et al . CHK1 is required for spindle checkpoint function. Dev Cell 2007; 12:247–60. Google Scholar
  206. 104
  207. S Peddibhotla MH Lam M Gonzalez-Rimbau JM Rosen The DNA-damage effector checkpoint kinase 1 is essential for chromosome segregation and cytokinesis. Proc Natl Acad Sci U S A 2009; 106:5159–64. Google Scholar
  208. 105
  209. G Iliakis Y Wang J Guan H Wang DNA damage checkpoint control in cells exposed to ionizing radiation. Oncogene 2003; 22:5834–47. Google Scholar
  210. 106
  211. F Bunz A Dutriaux C Lengauer T Waldman S Zhou JP Brown et al . Requirement for p53 and p21 to sustain G2 arrest after DNA damage. Science 1998; 282:1497–501. Google Scholar
  212. 107
  213. C Imbriano A Gurtner F Cocchiarella S Di Agostino V Basile M Gostissa et al . Direct p53 transcriptional repression: in vivo analysis of CCAAT-containing G2/M promoters. Mol Cell Biol 2005; 25:3737–51. Google Scholar
  214. 108
  215. M Dalvai O Mondesert JC Bourdon B Ducommun C Dozier CDC25B is negatively regulated by p53 through Sp1 and NF-Y transcription factors. Oncogene 2011; 30:2282–8. Google Scholar
  216. 109
  217. L McKenzie S King L Marcar S Nicol SS Dias K Schumm et al . p53-dependent repression of polo-like kinase-1 (PLK1). Cell Cycle 2010; 9:4200–12. Google Scholar
  218. 110
  219. J Bartkova Z Horejsí K Koed A Krämer F Tort K Zieger et al . DNA damage response as a candidate anti-cancer barrier in early human tumorigenesis. Nature 2005; 434:864–70. Google Scholar
  220. 111
  221. VG Gorgoulis LV Vassiliou P Karakaidos P Zacharatos A Kotsinas T Liloglou et al . Activation of the DNA damage checkpoint and genomic instability in human precancerous lesions. Nature 2005; 434:907–13. Google Scholar
  222. 112
  223. SM Gollin Mechanisms leading to chromosomal instability. Semin Cancer Biol 2005; 15:33–42. Google Scholar
  224. 113
  225. JE Eyfjord SK Bodvarsdottir Genomic instability and cancer: networks involved in response to DNA damage. Mutat Res 2005; 592:18–28. Google Scholar
  226. 114
  227. KD Mills DO Ferguson FW Alt The role of DNA breaks in genomic instability and tumorigenesis. Immunol Rev 2003; 194:77–95. Google Scholar
  228. 115
  229. J Bartek J Bartkova J Lukas DNA damage signalling guards against activated oncogenes and tumour progression. Oncogene 2007; 26:7773–9. Google Scholar
  230. 116
  231. JH Hoeijmakers Genome maintenance mechanisms for preventing cancer. Nature 2001; 411:366–74. Google Scholar
  232. 117
  233. C Barlow MA Eckhaus AA Schäffer A Wynshaw-Boris Atm haploinsufficiency results in increased sensitivity to sublethal doses of ionizing radiation in mice. Nat Genet 1999; 21:359–60. Google Scholar
  234. 118
  235. Y Fang CC Tsao BK Goodman R Furumai CA Tirado RT Abraham et al . ATR functions as a gene dosage-dependent tumor suppressor on a mismatch repair-deficient background. EMBO J 2004; 23:3164–74. Google Scholar
  236. 119
  237. A Celeste S Difilippantonio MJ Difilippantonio O Fernandez-Capetillo DR Pilch OA Sedelnikova et al . H2AX haploinsufficiency modifies genomic stability and tumor susceptibility. Cell 2003; 114:371–83. Google Scholar
  238. 120
  239. CH Bassing H Suh DO Ferguson KF Chua J Manis M Eckersdorff et al . Histone H2AX: a dosage-dependent suppressor of oncogenic translocations and tumors. Cell 2003; 114:359–70. Google Scholar
  240. 121
  241. MH Lam Q Liu SJ Elledge JM Rosen CHK1 is haploinsufficient for multiple functions critical to tumor suppression. Cancer Cell 2004; 6:45–59. Google Scholar
  242. 122
  243. S Difilippantonio A Celeste O Fernandez-Capetillo HT Chen B Reina San Martin F Van-Laethem et al . Role of Nbs1 in the activation of the Atm kinase revealed in humanized mouse models. Nat Cell Biol 2005; 7:675–85. Google Scholar
  244. 123
  245. Y Zhang CU Lim ES Williams J Zhou Q Zhang MH Fox et al . NBS1 knockdown by small interfering RNA increases ionizing radiation mutagenesis and telomere association in human cells. Cancer Res 2005; 65:5544–53. Google Scholar
  246. 124
  247. AS Balajee CR Geard Replication protein A and gamma-H2AX foci assembly is triggered by cellular response to DNA double-strand breaks. Exp Cell Res 2004; 300:320–34. Google Scholar
  248. 125
  249. Y Wang CD Putnam MF Kane W Zhang L Edelmann R Russell et al . Mutation in Rpa1 results in defective DNA double-strand break repair, chromosomal instability and cancer in mice. Nat Genet 2005; 37:750–5. Google Scholar
  250. 126
  251. M Budzowska I Jaspers J Essers H de Waard E van Drunen K Hanada et al . Mutation of the mouse Rad17 gene leads to embryonic lethality and reveals a role in DNA damage-dependent recombination. EMBO J 2004; 23:3548–58. Google Scholar
  252. 127
  253. SX Shen Z Weaver X Xu C Li M Weinstein L Chen et al . A targeted disruption of the murine Brca1 gene causes gamma-irradiation hypersensitivity and genetic instability. Oncogene 1998; 17:3115–24. Google Scholar
  254. 128
  255. A Tutt A Ashworth The relationship between the roles of BRCA genes in DNA repair and cancer predisposition. Trends Mol Med 2002; 8:571–6. Google Scholar
  256. 129
  257. LB Smilenov HB Lieberman SA Mitchell RA Baker KM Hopkins EJ Hall Combined haploinsufficiency for ATM and RAD9 as a factor in cell transformation, apoptosis, and DNA lesion repair dynamics. Cancer Res 2005; 65:933–8. Google Scholar
  258. 130
  259. G Balmus M Zhu S Mukherjee AM Lyndaker KR Hume J Lee ML Riccio AP Reeves et al . Disease severity in a mouse model of ataxia telangiectasia is modulated by the DNA damage checkpoint gene Hus1. Hum Mol Genet 2012; 21:3408–20. Google Scholar
  260. 131
  261. H Wang H Wang SN Powell G Iliakis Y Wang ATR affecting cell radiosensitivity is dependent on homologous recombination repair but independent of nonhomologous end joining. Cancer Res 2004; 64:7139–43. Google Scholar
  262. 132
  263. CS Sørensen LT Hansen J Dziegielewski RG Syljuåsen C Lundin J Bartek et al . The cell-cycle checkpoint kinase CHK1 is required for mammalian homologous recombination repair. Nat Cell Biol 2005; 7:195–201. Google Scholar
  264. 133
  265. B Hu H Wang X Wang HR Lu C Huang SN Powell et al . hit and CHK1 have opposing effects on homologous recombination repair. Cancer Res 2005; 65:8613–6. Google Scholar
  266. 134
  267. CS Sørensen RG Syljuåsen J Falck T Schroeder L Rönnstrand KK Khanna et al . CHK1 regulates the S phase checkpoint by coupling the physiological turnover and ionizing radiation-induced accelerated proteolysis of CDC25A. Cancer Cell 2003; 3:247–58. Google Scholar
  268. 135
  269. WA Cliby CJ Roberts KA Cimprich CM Stringer JR Lamb SL Schreiber et al . Overexpression of a kinase-inactive ATR protein causes sensitivity to DNA-damaging agents and defects in cell cycle checkpoints. EMBO J 1998; 17:159–69. Google Scholar
  270. 136
  271. E Petermann A Maya-Mendoza G Zachos DA Gillespie DA Jackson KW Caldecott CHK1 requirement for high global rates of replication fork progression during normal vertebrate S phase. Mol Cell Biol 2006; 26:3319–26. Google Scholar
  272. 137
  273. E Petermann M Woodcock T Helleday CHK1 promotes replication fork progression by controlling replication initiation. Proc Natl Acad Sci U S A 2010; 107:16090–5. Google Scholar
  274. 138
  275. C Feijoo C Hall-Jackson R Wu D Jenkins J Leitch DM Gilbert et al . Activation of mammalian CHK1 during DNA replication arrest: a role for CHK1 in the intra-S phase checkpoint monitoring replication origin firing. J Cell Biol 2001; 154:913–23. Google Scholar
  276. 139
  277. RD Paulsen KA Cimprich The ATR pathway: fine-tuning the fork. DNA Repair (Amst) 2007; 6:953–66. Google Scholar
  278. 140
  279. P Zhang J Wang W Gao BZ Yuan J Rogers E Reed CHK2 kinase expression is down-regulated due to promoter methylation in non-small cell lung cancer. Mol Cancer 2004; 3:14. Google Scholar
  280. 141
  281. F Bertoni AM Codegoni D Furlan MG Tibiletti C Capella M Broggini CHK1 frameshift mutations in genetically unstable colorectal and endometrial cancers. Genes Chromosomes Cancer 1999; 26:176–80. Google Scholar
  282. 142
  283. KA Lewis S Mullany B Thomas J Chien R Loewen V Shridhar et al . Heterozygous ATR mutations in mismatch repair-deficient cancer cells have functional significance. Cancer Res 2005; 65:7091–5. Google Scholar
  284. 143
  285. A Menoyo H Alazzouzi E Espín M Armengol H Yamamoto S Schwartz Jr Somatic mutations in the DNA damage-response genes ATR and CHK1 in sporadic stomach tumors with microsatellite instability. Cancer Res 2001; 61:7727–30. Google Scholar
  286. 144
  287. T Fishler YY Li RH Wang HS Kim K Sengupta A Vassilopoulos et al . Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of CHK1 and p53. Oncogene 2010; 29:4007–17. Google Scholar
  288. 145
  289. MA van Vugt RH Medema Getting in and out of mitosis with Polo-like kinase-1. Oncogene 2005; 24:2844–59. Google Scholar
  290. 146
  291. H Katayama S Sen Aurora kinase inhibitors as anticancer molecules. Biochim Biophys Acta 2010; 1799:829–39. Google Scholar
  292. 147
  293. M Canavese L Santo N Raje Cyclin dependent kinases in cancer: potential for therapeutic intervention. Cancer Biol Ther 2012; 13:451–7. Google Scholar
  294. 148
  295. K Galaktionov AK Lee J Eckstein G Draetta J Meckler M Loda et al . CDC25 phosphatases as potential human oncogenes. Science 1995; 269:1575–7. Google Scholar
  296. 149
  297. S Backert M Gelos U Kobalz ML Hanski C Böhm B Mann et al . Differential gene expression in colon carcinoma cells and tissues detected with a cDNA array. Int J Cancer 1999; 82:868–74. Google Scholar
  298. 150
  299. T Yoshida S Tanaka A Mogi Y Shitara H Kuwano The clinical significance of Cyclin B1 and Wee1 expression in non-small-cell lung cancer. Ann Oncol 2004; 15:252–6. Google Scholar
  300. 151
  301. HC Hwang BE Clurman Cyclin E in normal and neoplastic cell cycles. Oncogene 2005; 24:2776–86. Google Scholar
  302. 152
  303. CH Spruck KA Won SI Reed Deregulated cyclin E induces chromosome instability. Nature 1999; 401:297–300. Google Scholar
  304. 153
  305. S Valastyan RA Weinberg Tumor metastasis: molecular insights and evolving paradigms. Cell 2011; 147:275–92. Google Scholar
  306. 154
  307. LA Mathews SM Cabarcas WL Farrar DNA repair: the culprit for tumor-initiating cell survival? Cancer Metastasis Rev 2011; 30:185–97. Google Scholar
  308. 155
  309. V Winnepenninckx V Lazar S Michiels P Dessen M Stas SR Alonso et al . Gene expression profiling of primary cutaneous melanoma and clinical outcome. J Natl Cancer Inst 2006; 98:472–82. Google Scholar
  310. 156
  311. A Kauffmann F Rosselli V Lazar V Winnepenninckx A Mansuet-Lupo P Dessen et al . High expression of DNA repair pathways is associated with metastasis in melanoma patients. Oncogene 2008; 27:565–73. Google Scholar
  312. 157
  313. A Sarasin A Kauffmann Overexpression of DNA repair genes is associated with metastasis: a new hypothesis. Mutat Res 2008; 659:49–55. Google Scholar
  314. 158
  315. T Taniguchi M Tischkowitz N Ameziane SV Hodgson CG Mathew H Joenje et al . Disruption of the Fanconi anemia-BRCA pathway in cisplatin-sensitive ovarian tumors. Nat Med 2003; 9:568–74. Google Scholar
  316. 159
  317. H Niida M Nakanishi DNA damage checkpoints in mammals. Mutagenesis 2006; 21:3–9. Google Scholar
  318. 160
  319. CG Broustas HB Lieberman Contributions of Rad9 to tumorigenesis. J Cell Biochem 2012; 113:742–51. Google Scholar
  320. 161
  321. M Toueille N El-Andaloussi I Frouin R Freire D Funk I Shevelev et al . The human Rad9/Rad1/Hus1 damage sensor clamp interacts with DNA polymerase beta and increases its DNA substrate utilization efficiency: Implications for DNA repair. Nucleic Acids Res 2004; 32:3316–24. Google Scholar
  322. 162
  323. W Wang P Brandt RA Bambara The human Rad9-Rad1-Hus1 checkpoint complex stimulates flap endonuclease 1. Proc Natl Acad Sci U S A 2004; 101:16762–7. Google Scholar
  324. 163
  325. T Li Z Wang Y Zhao W He L An S Liu et al . Checkpoint protein Rad9 plays an important role in nucleotide excision repair. DNA Repair (Amst) 2013; 12:284–92. Google Scholar
  326. 164
  327. W He Y Zhao C Zhang L An Z Hu Y Liu et al . Rad9 plays an important role in DNA mismatch repair through physical interaction with MLH1. Nucleic Acids Res 2008; 36:6406–17. Google Scholar
  328. 165
  329. RK Pandita GG Sharma A Laszlo KM Hopkins S Davey M Chakhparonian et al . Mammalian Rad9 plays a role in telomere stability, S- and G2-phase-specific cell survival, and homologous recombinational repair. Mol Cell Biol 2006; 26:1850–64. Google Scholar
  330. 166
  331. C Günes KL Rudolph The role of telomeres in stem cells and cancer. Cell 2013; 152:390–3. Google Scholar
  332. 167
  333. R Riboni A Casati T Nardo E Zaccaro L Ferretti F Nuzzo et al . Telomeric fusions in cultured human fibroblasts as a source of genomic instability. Cancer Genet Cytogenet 1997; 95:130–6. Google Scholar
  334. 168
  335. AK Meeker P Argani Telomere shortening occurs early during breast tumorigenesis: a cause of chromosome destabilization underlying malignant transformation? J Mammary Gland Biol Neoplasia 2004; 9:285–96. Google Scholar
  336. 169
  337. SA Stewart RA Weinberg Telomeres: cancer to human aging. Annu Rev Cell Dev Biol 2006; 22:531–57. Google Scholar
  338. 170
  339. KM Hopkins W Auerbach XY Wang MP Hande H Hang DJ Wolgemuth et al . Deletion of mouse rad9 causes abnormal cellular responses to DNA damage, genomic instability, and embryonic lethality. Mol Cell Biol 2004; 24:7235–48. Google Scholar
  340. 171
  341. A Zhu H Zhou C Leloup SA Marino CR Geard TK Hei HB Lieberman Differential impact of mouse Rad9 deletion on ionizing radiation-induced bystander effects. Radiat Res 2005; 164:655–61. Google Scholar
  342. 172
  343. K Komatsu T Miyashita H Hang KM Hopkins W Zheng S Cuddeback et al . Human homologue of S. pombe Rad9 interacts with BCL-2/BCL-xL and promotes apoptosis. Nat Cell Biol 2000; 2:1–6. Google Scholar
  344. 173
  345. H Ishii T Inageta K Mimori T Saito H Sasaki M Isobe et al . Frag1, a homolog of alternative replication factor C subunits, links replication stress surveillance with apoptosis. Proc Natl Acad Sci U S A 2005; 102:9655–60. Google Scholar
  346. 174
  347. K Yoshida K Komatsu HG Wang D Kufe . c-Abl tyrosine kinase regulates the human Rad9 checkpoint protein in response to DNA damage. Mol Cell Biol 2002; 22:3292–300. Google Scholar
  348. 175
  349. K Yoshida HG Wang Y Miki D Kufe Protein kinase Cdelta is responsible for constitutive and DNA damage-induced phosphorylation of Rad9. EMBO J 2003; 22:1431–41. Google Scholar
  350. 176
  351. O Gressner T Schilling K Lorenz E Schulze Schleithoff A Koch et al . TAp63alpha induces apoptosis by activating signaling via death receptors and mitochondria. EMBO J 2005; 24:2458–71. Google Scholar
  352. 177
  353. Y Yin A Zhu YJ Jin YX Liu X Zhang KM Hopkins et al . Human RAD9 checkpoint control/proapoptotic protein can activate transcription of p21. Proc Natl Acad Sci U S A 2004; 101:8864–9. Google Scholar
  354. 178
  355. L Wang CL Hsu J Ni PH Wang S Yeh P Keng et al . Human checkpoint protein hRad9 functions as a negative coregulator to repress androgen receptor transactivation in prostate cancer cells. Mol Cell Biol 2004; 24:2202–13. Google Scholar
  356. 179
  357. A Zhu CX Zhang HB Lieberman Rad9 has a functional role in human prostate carcinogenesis. Cancer Res 2008; 68:1267–74. Google Scholar
  358. 180
  359. JD Hood DA Cheresh Role of integrins in cell invasion and migration. Nat Rev Cancer 2002; 2:91–100. Google Scholar
  360. 181
  361. ZZ Zeng Y Jia NJ Hahn SM Markwart KF Rockwood DL Livant Role of focal adhesion kinase and phosphatidylinositol 3′-kinase in integrin fibronectin receptor-mediated, matrix metalloproteinase-1-dependent invasion by metastatic prostate cancer cells. Cancer Res 2006; 66:8091–9. Google Scholar
  362. 182
  363. BD Manning LC Cantley AKT/PKB signaling: navigating downstream. Cell 2007; 129:1261–74. Google Scholar
  364. 183
  365. CG Broustas A Zhu HB Lieberman Rad9 protein contributes to prostate tumor progression by promoting cell migration and anoikis resistance. J Biol Chem 2012; 287:41324–33. Google Scholar
  366. 184
  367. YP Yu D Landsittel L Jing J Nelson B Ren L Liu et al . Gene expression alterations in prostate cancer predicting tumor aggression and preceding development of malignancy. J Clin Oncol 2004; 22:2790–9. Google Scholar
  368. 185
  369. S Varambally J Yu B Laxman DR Rhodes R Mehra SA Tomlins et al . Integrative genomic and proteomic analysis of prostate cancer reveals signatures of metastatic progression. Cancer Cell 2005; 8:393–406. Google Scholar
  370. 186
  371. UR Chandran C Ma R Dhir M Bisceglia M Lyons-Weiler W Liang et al . Gene expression profiles of prostate cancer reveal involvement of multiple molecular pathways in the metastatic process. BMC Cancer 2007; 7:64. Google Scholar
  372. 187
  373. X Wang L Zou T Lu S Bao KE Hurov WN Hittelman et al . Rad17 phosphorylation is required for claspin recruitment and Chk1 activation in response to replication stress. Mol Cell 2006; 23:331–41. Google Scholar
  374. 188
  375. S Bao RS Tibbetts KM Brumbaugh Y Fang DA Richardson A Ali et al . ATR/ATM-mediated phosphorylation of human Rad17 is required for genotoxic stress responses. Nature 2001; 411:969–74. Google Scholar
  376. 189
  377. A Bric C Miething CU Bialucha C Scuoppo L Zender A Krasnitz et al . Functional identification of tumor-suppressor genes through an in vivo RNA interference screen in a mouse lymphoma model. Cancer Cell 2009; 16:324–35. Google Scholar
  378. 190
  379. M Zhao S Begum PK Ha W Westra J Califano Downregulation of RAD17 in head and neck cancer. Head Neck 2008; 30:35–42. Google Scholar
  380. 191
  381. Z Zhou C Jing L Zhang F Takeo H Kim Y Huang et al . Regulation of Rad17 Protein Turnover Unveils an Impact of Rad17-APC Cascade in Breast Carcinogenesis and Treatment. J Biol Chem 2013; 288:18134–45. Google Scholar
  382. 192
  383. X Wang L Wang MD Callister JB Putnam L Mao L Li Human Rad17 is phosphorylated upon DNA damage and also overexpressed in primary non-small cell lung cancer tissues. Cancer Res 2001; 61:7417–21. Google Scholar
  384. 193
  385. H Sasaki LB Chen D Auclair S Moriyama M Kaji I Fukai et al . Overexpression of Hrad17 gene in non-small cell lung cancers correlated with lymph node metastasis. Lung Cancer 2001; 34:47–52. Google Scholar
  386. 194
  387. S Bao T Lu X Wang H Zheng LE Wang Q Wei et al . Disruption of the Rad9/Rad1/Hus1 (9-1-1) complex leads to checkpoint signaling and replication defects. Oncogene 2004; 23:5586–93. Google Scholar
  388. 195
  389. CL Meyerkord Y Takahashi R Araya N Takada RS Weiss HG Wang Loss of Hus1 sensitizes cells to etoposide-induced apoptosis by regulating BH3-only proteins. Oncogene 2008; 27:7248–59. Google Scholar
  390. 196
  391. B Kinzel J Hall F Natt J Weiler D Cohen Downregulation of Hus1 by antisense oligonucleotides enhances the sensitivity of human lung carcinoma cells to cisplatin. Cancer 2002; 94:1808–14. Google Scholar
  392. 197
  393. PD Brandt CE Helt PC Keng RA Bambara The Rad9 protein enhances survival and promotes DNA repair following exposure to ionizing radiation. Biochem Biophys Res Commun 2006; 347:232–7. Google Scholar
  394. 198
  395. X Wang B Hu RS Weiss Y Wang The effect of Hus1 on ionizing radiation sensitivity is associated with homologous recombination repair but is independent of nonhomologous end-joining. Oncogene 2006; 25:1980–3. Google Scholar
  396. 199
  397. J de la Torre A Gil-Moreno A García F Rojo J Xercavins E Salido et al . Expression of DNA damage checkpoint protein Hus1 in epithelial ovarian tumors correlates with prognostic markers. Int J Gynecol Pathol 2008; 27:24–32. Google Scholar
  398. 200
  399. L Han Z Hu Y Liu X Wang KM Hopkins HB Lieberman et al . Mouse Rad1 deletion enhances susceptibility for skin tumor development. Mol Cancer 2010; 9:67. Google Scholar
  400. 201
  401. BW Durkacz O Omidiji DA Gray S Shall (ADP-ribose)n participates in DNA excision repair. Nature 1980; 283:593–6. Google Scholar
  402. 202
  403. R Krishnakumar WL Kraus The PARP side of the nucleus: molecular actions, physiological outcomes, and clinical targets. Mol Cell 2010; 39:8–24. Google Scholar
  404. 203
  405. A Gonçalves P Finetti R Sabatier M Gilabert J Adelaide JP Borg et al . Poly(ADP-ribose) polymerase-1 mRNA expression in human breast cancer: a meta-analysis. Breast Cancer Res Treat 2011; 127:273–81. Google Scholar
  406. 204
  407. JC Brenner B Ateeq Y Li AK Yocum Q Cao IA Asangani et al . Mechanistic rationale for inhibition of poly(ADP-ribose) polymerase in ETS gene fusion-positive prostate cancer. Cancer Cell 2011; 19:664–78. Google Scholar
  408. 205
  409. MJ Schiewer JF Goodwin S Han JC Brenner MA Augello JL Dean et al . Dual roles of PARP-1 promote cancer growth and progression. Cancer Discov 2012; 2:1134–49. Google Scholar
  410. 206
  411. SA Tomlins DR Rhodes S Perner SM Dhanasekaran R Mehra XW Sun et al . Recurrent fusion of TMPRSS2 and ETS transcription factor genes in prostate cancer. Science 2005; 310:644–8. Google Scholar
  412. 207
  413. A Gopalan MA Leversha JM Satagopan Q Zhou HA Al-Ahmadie SW Fine et al . TMPRSS2-ERG gene fusion is not associated with outcome in patients treated by prostatectomy. Cancer Res 2009; 69:1400–6. Google Scholar
  414. 208
  415. MI Rodríguez A González-Flores F Dantzer J Collard AG de Herreros FJ Oliver Poly(ADP-ribose)-dependent regulation of Snail1 protein stability. Oncogene 2011; 30:4365–72. Google Scholar
  416. 209
  417. MA Nieto The snail superfamily of zinc-finger transcription factors. Nat Rev Mol Cell Biol 2002; 3:155–166. Google Scholar
  418. 210
  419. TR McPhee PC McDonald A Oloumi S Dedhar Integrin-linked kinase regulates E-cadherin expression through PARP-1. Dev Dyn 2008; 237:2737–47. Google Scholar
  420. 211
  421. J Stanisavljevic M Porta-de-la-Riva R Batlle AG de Herreros J Baulida The p65 subunit of NF-κB and PARP1 assist Snail1 in activating fibronectin transcription. J Cell Sci 2011; 124:4161–71. Google Scholar
  422. 212
  423. P Lönn LP van der Heide M Dahl U Hellman CH Heldin A Moustakas PARP-1 attenuates Smad-mediated transcription. Mol Cell 2010; 40:521–32. Google Scholar
  424. 213
  425. ME Moynahan JW Chiu BH Koller M Jasin Brca1 controls homology-directed DNA repair. Mol Cell 1999; 4(4):511–8. Google Scholar
  426. 214
  427. A Tutt A Gabriel D Bertwistle F Connor H Paterson J Peacock et al . Absence of Brca2 causes genome instability by chromosome breakage and loss associated with centrosome amplification. Curr Biol 1999; 9:1107–10. Google Scholar
  428. 215
  429. CX Deng BRCA1: cell cycle checkpoint, genetic instability, DNA damage response and cancer evolution. Nucleic Acids Res 2006; 34:1416–26. Google Scholar
  430. 216
  431. JJ Gorski KI Savage JM Mulligan SS McDade JK Blayney Z Ge et al . Profiling of the BRCA1 transcriptome through microarray and ChIP-chip analysis. Nucleic Acids Res 2011; 39:9536–48. Google Scholar
  432. 217
  433. KW Kinzler B Vogelstein Cancer-susceptibility genes. Gatekeepers and caretakers. Nature 1997; 386:761, 763. Google Scholar
  434. 218
  435. AN Monteiro BRCA1: exploring the links to transcription. Trends Biochem Sci 2000; 25:469–74. Google Scholar
  436. 219
  437. Y Wang J Yu Q Zhan BRCA1 regulates caveolin-1 expression and inhibits cell invasiveness. Biochem Biophys Res Commun 2008; 370:201–6. Google Scholar
  438. 220
  439. ED Coene C Gadelha N White A Malhas B Thomas M Shaw et al . A novel role for BRCA1 in regulating breast cancer cell spreading and motility. J Cell Biol 2011; 192:497–512 Google Scholar
  440. 221
  441. H Zhu J Yue Z Pan H Wu Y Cheng H Lu et al . Involvement of Caveolin-1 in repair of DNA damage through both homologous recombination and non-homologous end joining. PLoS One 2010; 5(8):e12055. Google Scholar
  442. 222
  443. ME Moynahan AJ Pierce M Jasin BRCA2 is required for homology-directed repair of chromosomal breaks. Mol Cell 2001; 7:263–72. Google Scholar
  444. 223
  445. J Milner B Ponder L Hughes-Davies M Seltmann T Kouzarides Transcriptional activation functions in BRCA2. Nature 1997; 386:772–3. Google Scholar
  446. 224
  447. MJ Daniels Y Wang M Lee AR Venkitaraman Abnormal cytokinesis in cells deficient in the breast cancer susceptibility protein BRCA2. Science 2004; 306:876–9. Google Scholar
  448. 225
  449. V Costanzo Brca2, Rad51 and Mre11: performing balancing acts on replication forks. DNA Repair (Amst) 2011; 10:1060–5. Google Scholar
  450. 226
  451. SC Wang R Shao AY Pao S Zhang MC Hung LK Su Inhibition of cancer cell growth by BRCA2. Cancer Res 2002; 62:1311–4. Google Scholar
  452. 227
  453. L Moro AA Arbini E Marra M Greco Down-regulation of BRCA2 expression by collagen type I promotes prostate cancer cell proliferation. J Biol Chem 2005; 280:22482–91. Google Scholar
  454. 228
  455. L Moro AA Arbini E Marra M Greco Up-regulation of Skp2 after prostate cancer cell adhesion to basement membranes results in BRCA2 degradation and cell proliferation. J Biol Chem 2006; 281:22100–7 Google Scholar
  456. 229
  457. L Moro AA Arbini JL Yao PA di Sant'Agnese E Marra M Greco Loss of BRCA2 promotes prostate cancer cell invasion through up-regulation of matrix metalloproteinase-9. Cancer Sci 2008; 99:553–63. Google Scholar
  458. 230
  459. E Castro C Goh D Olmos E Saunders D Leongamornlert M Tymrakiewicz et al . Germline BRCA mutations are associated with higher risk of nodal involvement, distant metastasis, and poor survival outcomes in prostate cancer. J Clin Oncol 2013; 31:1748–57. Google Scholar
  460. 231
  461. I Demuth M Digweed The clinical manifestation of a defective response to DNA double-strand breaks as exemplified by Nijmegen breakage syndrome. Oncogene 2007; 26:7792–8. Google Scholar
  462. 232
  463. TH Stracker JH Petrini The MRE11 complex: starting from the ends. Nat Rev Mol Cell Biol 2011; 12:90–103. Google Scholar
  464. 233
  465. P Karran DNA double strand break repair in mammalian cells. Curr Opin Genet Dev.2000; 10:144–50. Google Scholar
  466. 234
  467. JH Petrini The Mre11 complex and ATM: collaborating to navigate S phase. Curr Opin Cell Biol 2000; 12:293–6. Google Scholar
  468. 235
  469. YC Chiang SC Teng YN Su FJ Hsieh KJ Wu . c-Myc directly regulates the transcription of the NBS1 gene involved in DNA double-strand break repair. J Biol Chem 2003; 278:19286–91. Google Scholar
  470. 236
  471. YC Chen YN Su PC Chou WC Chiang MC Chang et al . Overexpression of NBS1 contributes to transformation through the activation of phosphatidylinositol 3-kinase/Akt. J Biol Chem 2005; 280:32505–11. Google Scholar
  472. 237
  473. D D'Amours SP Jackson The Mre11 complex: at the crossroads of DNA repair and checkpoint signalling. Nat Rev Mol Cell Biol 2002; 3:317–27. Google Scholar
  474. 238
  475. MH Yang SY Chang SH Chiou CJ Liu CW Chi PM Chen et al . Overexpression of NBS1 induces epithelial-mesenchymal transition and co-expression of NBS1 and Snail predicts metastasis of head and neck cancer. Oncogene 2007; 26:1459–67. Google Scholar
  476. 239
  477. CY Wu CT Lin MZ Wu KJ Wu Induction of HSPA4 and HSPA14 by NBS1 overexpression contributes to NBS1-induced in vitro metastatic and transformation activity. J Biomed Sci 2011; 18:1. Google Scholar
  478. 240
  479. R Wan DL Crowe Haploinsufficiency of the Nijmegen breakage syndrome 1 gene increases mammary tumor latency and metastasis. Int J Oncol 2012; 41:345–52. Google Scholar
  480. 241
  481. HL Klein The consequences of Rad51 overexpression for normal and tumor cells. DNA Repair (Amst) 2008; 7:686–93. Google Scholar
  482. 242
  483. JY Wang T Ho J Trojanek J Chintapalli M Grabacka T Stoklosa et al . Impaired homologous recombination DNA repair and enhanced sensitivity to DNA damage in prostate cancer cells exposed to anchorage-independence. Oncogene 2005; 24:3748–58. Google Scholar
  484. 243
  485. VL Martinez-Marignac A Rodrigue D Davidson M Couillard AE Al-Moustafa M Abramovitz et al . The effect of a DNA repair gene on cellular invasiveness: XRCC3 over-expression in breast cancer cells. PLoS One 2011; 6(1):e16394. Google Scholar
  486. 244
  487. FA Derheimer MB Kastan Multiple roles of ATM in monitoring and maintaining DNA integrity. FEBS Lett 2010; 584:3675–81. Google Scholar
  488. 245
  489. M Sun X Guo X Qian H Wang C Yang KL Brinkman et al . Activation of the ATM-Snail pathway promotes breast cancer metastasis. J Mol Cell Biol 2012; 4:304–15. Google Scholar
  490. 246
  491. SE Golding E Rosenberg N Valerie I Hussaini M Frigerio XF Cockcroft et al . Improved ATM kinase inhibitor KU-60019 radiosensitizes glioma cells, compromises insulin, AKT and ERK prosurvival signaling, and inhibits migration and invasion. Mol Cancer Ther 2009; 8:2894–902. Google Scholar
  492. 247
  493. EH Sarsour MG Kumar L Chaudhuri AL Kalen PC Goswami Redox control of the cell cycle in health and disease. Antioxid Redox Signal 2009; 11:2985–3011. Google Scholar
  494. 248
  495. G Pani E Giannoni T Galeotti P Chiarugi Redox-based escape mechanism from death: the cancer lesson. Antioxid Redox Signal 2009; 11:2791–806. Google Scholar
  496. 249
  497. S Ditch TT Paull The ATM protein kinase and cellular redox signaling: beyond the DNA damage response. Trends Biochem Sci 2012; 37:15–22. Google Scholar
  498. 250
  499. YP Tsai KJ Wu Hypoxia-regulated target genes implicated in tumor metastasis. J Biomed Sci 2012; 19:102. Google Scholar
  500. 251
  501. ND Lakin SP Jackson Regulation of p53 in response to DNA damage. Oncogene 1999; 18:7644–55. Google Scholar
  502. 252
  503. SJ Baker AC Preisinger JM Jessup C Paraskeva S Markowitz JK Willson et al . p53 gene mutations occur in combination with 17p allelic deletions as late events in colorectal tumorigenesis. Cancer Res 1990; 50:7717–22. Google Scholar
  504. 253
  505. R Bookstein D MacGrogan SG Hilsenbeck F Sharkey DC Allred p53 is mutated in a subset of advanced-stage prostate cancers. Cancer Res 1993; 53:3369–73. Google Scholar
  506. 254
  507. RH Hruban M Goggins J Parsons SE Kern Progression model for pancreatic cancer. Clin Cancer Res 2000; 6:2969–72. Google Scholar
  508. 255
  509. P Hainaut M Hollstein p53 and human cancer: the first ten thousand mutations. Adv Cancer Res 2000; 77:81–137. Google Scholar
  510. 256
  511. W Hanel UM Moll Links between mutant p53 and genomic instability. J Cell Biochem 2012; 113:433–9. Google Scholar
  512. 257
  513. H Song M Hollstein Y Xu p53 gain-of-function cancer mutants induce genetic instability by inactivating ATM. Nat Cell Biol 2007; 9:573–80. Google Scholar
  514. 258
  515. DP Liu H Song Y Xu A common gain of function of p53 cancer mutants in inducing genetic instability. Oncogene 2010; 29:949–56. Google Scholar
  516. 259
  517. SR Hingorani L Wang AS Multani C Combs TB Deramaudt RH Hruban et al . Trp53R172H and KrasG12D cooperate to promote chromosomal instability and widely metastatic pancreatic ductal adenocarcinoma in mice. Cancer Cell 2005; 7:469–83. Google Scholar
  518. 260
  519. T Rausch DT Jones M Zapatka AM Stütz T Zichner J Weischenfeldt et al . Genome sequencing of pediatric medulloblastoma links catastrophic DNA rearrangements with TP53 mutations. Cell 2012; 148:59–71. Google Scholar
  520. 261
  521. LR Livingstone A White J Sprouse E Livanos T Jacks TD Tlsty Altered cell cycle arrest and gene amplification potential accompany loss of wild-type p53. Cell 1992; 70:923–35. Google Scholar
  522. 262
  523. Y Li C Prives Are interactions with p63 and p73 involved in mutant p53 gain of oncogenic function? Oncogene 2007; 26:2220–5. Google Scholar
  524. 263
  525. K Singh D Mogare RO Giridharagopalan R Gogiraju G Pande S Chattopadhyay p53 target gene SMAR1 is dysregulated in breast cancer: its role in cancer cell migration and invasion. PLoS One 2007; 2(7):e660. Google Scholar
  526. 264
  527. PA Muller KH Vousden JC Norman p53 and its mutants in tumor cell migration and invasion. J Cell Biol 2011; 192:209–18. Google Scholar
  528. 265
  529. PA Muller PT Caswell B Doyle MP Iwanicki EH Tan S Karim et al . Mutant p53 drives invasion by promoting integrin recycling. Cell 2009; 139:1327–41. Google Scholar
  530. 266
  531. T Shibue RA Weinberg Integrin beta1-focal adhesion kinase signaling directs the proliferation of metastatic cancer cells disseminated in the lungs. Proc Natl Acad Sci U S A 2009; 106:10290–5. Google Scholar
  532. 267
  533. L Huck SM Pontier DM Zuo Muller WJ. beta1-integrin is dispensable for the induction of ErbB2 mammary tumors but plays a critical role in the metastatic phase of tumor progression. Proc Natl Acad Sci U S A 2010; 107:15559–64. Google Scholar
  534. 268
  535. N Reymond JH Im R Garg FM Vega B Borda d'Agua P Riou et al . Cdc42 promotes transendothelial migration of cancer cells through β1 integrin. J Cell Biol 2012; 199:653–68. Google Scholar
  536. 269
  537. PT Caswell S Vadrevu JC Norman Integrins: masters and slaves of endocytic transport. Nat Rev Mol Cell Biol 2009; 10:843–53. Google Scholar
  538. 270
  539. ML Smith IT Chen Q Zhan I Bae CY Chen TM Gilmer et al . Interaction of the p53-regulated protein Gadd45 with proliferating cell nuclear antigen. Science 1994; 266:1376–80. Google Scholar
  540. 271
  541. J Hildesheim DV Bulavin MR Anver WG Alvord MC Hollander L Vardanian et al . Gadd45a protects against UV irradiation-induced skin tumors, and promotes apoptosis and stress signaling via MAPK and p53. Cancer Res 2002; 62:7305–15. Google Scholar
  542. 272
  543. K Yamasawa Y Nio M Dong K Yamaguchi M Itakura Clinicopathological significance of abnormalities in Gadd45 expression and its relationship to p53 in human pancreatic cancer. Clin Cancer Res 2002; 8:2563–9. Google Scholar
  544. 273
  545. W Wang G Huper Y Guo SK Murphy JA Olson Jr JR Marks Analysis of methylation-sensitive transcriptome identifies GADD45a as a frequently methylated gene in breast cancer. Oncogene 2005; 24:2705–14. Google Scholar
  546. 274
  547. J Ji R Liu T Tong Y Song S Jin M Wu et al . Gadd45a regulates beta-catenin distribution and maintains cell-cell adhesion/contact. Oncogene 2007; 26:6396–405. Google Scholar
  548. 275
  549. Z Shan G Li Q Zhan D Li Gadd45a inhibits cell migration and invasion by altering the global RNA expression. Cancer Biol Ther 2012; 13:1112–22. Google Scholar
  550. 276
  551. N Marino J Nakayama JW Collins PS Steeg Insights into the biology and prevention of tumor metastasis provided by the Nm23 metastasis suppressor gene. Cancer Metastasis Rev 2012; 31:593–603. Google Scholar
  552. 277
  553. VA Flørenes S Aamdal O Myklebost GM Maelandsmo OS Bruland O Fodstad Levels of nm23 messenger RNA in metastatic malignant melanomas: inverse correlation to disease progression. Cancer Res 1992; 52:6088–91. Google Scholar
  554. 278
  555. Q Zhang JR McCorkle M Novak M Yang DM Kaetzel Metastasis suppressor function of NM23-H1 requires its 3′-5′ exonuclease activity. Int J Cancer 2011; 128:40–50. Google Scholar
  556. 279
  557. SG Jarrett M Novak S Dabernat JY Daniel I Mellon Q Zhang et al . Metastasis suppressor NM23-H1 promotes repair of UV-induced DNA damage and suppresses UV-induced melanomagenesis. Cancer Res 2012; 72:133–43. Google Scholar
  558. 280
  559. M Chaplet R Rai D Jackson-Bernitsas K Li SY Lin BRIT1/MCPH1: a guardian of genome and an enemy of tumors. Cell Cycle 2006; 5:2579–83. Google Scholar
  560. 281
  561. LJ van 't-Veer H Dai MJ van de Vijver YD He Hart AA M Mao et al . Gene expression profiling predicts clinical outcome of breast cancer. Nature 2002; 415:530–6. Google Scholar
  562. 282
  563. R Rai H Dai AS Multani K Li K Chin J Gray et al . BRIT1 regulates early DNA damage response, chromosomal integrity, and cancer. Cancer Cell 2006; 10:145–57. Google Scholar
  564. 283
  565. B Yi SX Tan CE Tang WG Huang AL Cheng C Li et al . Inactivation of 14-3-3 sigma by promoter methylation correlates with metastasis in nasopharyngeal carcinoma. J Cell Biochem 2009; 106:858–66. Google Scholar
  566. 284
  567. XQ Wang YQ Zhu KS Lui Q Cai P Lu RT Poon Aberrant Polo-like kinase 1-CDC25A pathway in metastatic hepatocellular carcinoma. Clin Cancer Res 2008; 14:6813–20. Google Scholar
  568. 285
  569. M Squatrito C Gorrini B Amati Tip60 in DNA damage response and growth control: many tricks in one HAT. Trends Cell Biol 2006; 16:433–42. Google Scholar
  570. 286
  571. Y Sun X Jiang S Chen N Fernandes BD Price A role for the Tip60 histone acetyltransferase in the acetylation and activation of ATM. Proc Natl Acad Sci U S A 2005; 102:13182–7. Google Scholar
  572. 287
  573. ME Lleonart F Vidal D Gallardo M Diaz-Fuertes F Rojo M Cuatrecasas et al . New p53 related genes in human tumors: significant downregulation in colon and lung carcinomas. Oncol Rep 2000; 16:603–8. Google Scholar
  574. 288
  575. K Sakuraba T Yasuda M Sakata YH Kitamura A Shirahata T Goto et al . Down-regulation of Tip60 gene as a potential marker for the malignancy of colorectal cancer. Anticancer Res 2009; 29:3953–5. Google Scholar
  576. 289
  577. G Chen Y Cheng Y Tang M Martinka G Li Role of Tip60 in human melanoma cell migration, metastasis, and patient survival. J Invest Dermatol 2012; 132:2632–41. Google Scholar
  578. 290
  579. WM Bonner CE Redon JS Dickey AJ Nakamura OA Sedelnikova S Solier et al . GammaH2AX and cancer. Nat Rev Cancer 2008; 8:957–67. Google Scholar
  580. 291
  581. M Economopoulou HF Langer A Celeste VV Orlova EY Choi M Ma et al . Histone H2AX is integral to hypoxia-driven neovascularization. Nat Med 2009; 15:553–8. Google Scholar
  582. 292
  583. EB Rankin AJ Giaccia EM Hammond Bringing H2AX into the angiogenesis family. Cancer Cell 2009; 15:459–61. Google Scholar
  584. 293
  585. Y Shiloh Y Ziv The ATM protein kinase: regulating the cellular response to genotoxic stress, and more. Nat Rev Mol Cell Biol 2013; 14:197–210. Google Scholar

FIG. 1.

The multiple functions of DNA damage response and repair genes. Many genes discussed in this review have at least a subset of the activities depicted. For more details see Tables I and II.



Functional Roles of DNA Damage Response and Repair Genes



Role of DNA Damage Response and Repair Genes in Tumor Growth and Metastasis

Constantinos G. Broustas and Howard B. Lieberman "DNA Damage Response Genes and the Development of Cancer Metastasis," Radiation Research 181(2), (7 January 2014).
Received: 15 August 2013; Accepted: 1 October 2013; Published: 7 January 2014

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