Yiin, J. H., Anderson, J. L., Daniels, R. D., Seel, E. A., Fleming, D. A., Waters, K. M. and Chen, P-H. A Nested Case-Control Study of Multiple Myeloma Risk and Uranium Exposure among Workers at the Oak Ridge Gaseous Diffusion Plant. Radiat. Res. 171, 637–645 (2009).

The primary risk factors of multiple myeloma are age, race and sex, but several studies have found an association between radiological hazards and multiple myeloma. The purpose of this nested case-control study was to investigate whether workers with chronic low-level exposure to internally deposited uranium at the Oak Ridge Gaseous Diffusion Plant in eastern Tennessee were at higher risk of dying of multiple myeloma than those without occupational exposure to uranium, with the consideration of potential confounders of external ionizing radiation and occupational chemical hazards such as mercury, nickel and trichloroethylene. The main analyses were carried out using conditional logistic regression on 98 cases and 490 controls (five controls matched to each case on gender, race and age at risk). Our study showed a weak association between internal uranium dose estimated from urinalysis results and multiple myeloma risk: OR  =  1.04 (95% CI 1.00–1.09) at 10 µGy with the inclusion of other risk factors. The parameter estimates and the corresponding odds ratios were very similar when internal doses were imputed for subjects without urine samples. Further studies that include updating this cohort and combining with workers from other gaseous diffusion plants are needed to investigate the relationship between multiple myeloma risk and radiation or other chemical exposures.

Lu, X-Q. and Kiger, W. S., III. Application of a Novel Microdosimetry Analysis and its Radiobiological Implication for High-LET Radiation. Radiat. Res. 171, 646–656 (2009).

For short-range high-LET radiation therapy, the biological effects are strongly affected by the heterogeneity of the specific energy distribution delivered to tumor cells. Three-dimensional information at the cellular level is ideal for this type of study, but it is extremely difficult to obtain. In this paper, a novel microdosimetry analysis, which obtains the specific energy distribution directly from the morphological information in individual autoradiographic sections, is applied to in vivo human glioblastoma multiforme and normal brain tissue in boron neutron capture therapy. Specific energy distributions were obtained for both specimens, and they are consistent with a uniform boron microdistribution. We also used a biophysical model for cell survival analysis based on the specific energy and were able to bridge it with the model based on the corresponding macroscopic parameter (dose) using existing experimental data. The survival constant for the microscopic model was determined; cell survival curves were predicted for uniform and non-uniform source distributions, i.e., sources and cell nuclei bound together totally or only partially. The results indicate that the behavior of the survival curve can vary widely, which may have important clinical implications.

Chouin, N., Bernardeau, K., Davodeau, F., Chérel, M., Faivre-Chauvet, A., Bourgeois, M., Apostolidis, C., Morgenstern, A., Lisbona, A. and Bardiès, M. Evidence of Extranuclear Cell Sensitivity to Alpha-Particle Radiation Using a Microdosimetric Model. I. Presentation and Validation of a Microdosimetric Model. Radiat. Res. 171, 657–663 (2009).

A microdosimetric model that makes it possible to consider the numerous biological and physical parameters of cellular α-particle irradiation by radiolabeled mAbs was developed. It allows for the calculation of single-hit and multi-hit distributions of specific energy within a cell nucleus or a whole cell in any irradiation configuration. Cells are considered either to be isolated or to be packed in a monolayer or a spheroid. The method of calculating energy deposits is analytical and is based on the continuous-slowing-down approximation. A model of cell survival, calculated from the microdosimetric spectra and the microdosimetric radiosensitivity, z₀, was also developed. The algorithm of calculations was validated by comparison with two general Monte Carlo codes: MCNPX and Geant4. Microdosimetric spectra determined by these three codes showed good agreement for numerous geometrical configurations. The analytical method was far more efficient in terms of calculation time: A gain of more than 1000 was observed when using our model compared with Monte Carlo calculations. Good agreements were also observed with previously published results.

Chouin, N., Bernardeau, K., Bardiès, M. Chérel, Faivre-Chauvet, A., Bourgeois, M., Apostolidis, A., Morgenstern, A., Lisbona, A., Chérel, M. and Davodeau, F. Evidence of Extranuclear Cell Sensitivity to Alpha-Particle Radiation Using a Microdosimetric Model. II. Application of the Microdosimetric Model to Experimental Results. Radiat. Res. 171, 664–673 (2009).

A microdosimetric model was used to analyze the results of experimental studies on cells of two lymphoid cell lines (T2 and Ada) irradiated with ²¹³Bi-radiolabeled antibodies. These antibodies targeted MHC/peptide complexes. The density of target antigen could be modulated by varying the concentration of the peptide loaded onto the cells. This offered the possibility of changing the ratio of specific (from cell-bound antibody) to non-specific (from antibody present in the supernatant) irradiation. For both cell lines, survival plotted as a function of the mean absorbed dose was a decreasing exponential. For the T2 cells, the microdosimetric sensitivity calculated for the whole cell was equal whether the irradiation was non-specific (z₀ = 0.12 ± 0.02 Gy) or specific (z₀ = 0.12 ± 0.09 Gy). Similar results were obtained for Ada cells. These results constitute a biological validation of the microdosimetric model. For both cells, the measured cell mortality was greater than the percentage of hit cells calculated with the model at low mean absorbed doses. This observation thus suggests bystander effects. It poses the question of the relevance of the mean absorbed dose to the cell nuclei. A new concept in cellular dosimetry taking into account cytoplasm or membrane irradiation and bystander modeling appears to be needed.

Fritsch, P., Sérandour, A. L., Grémy, O., Phan, G., Tsapis, N., Abram, M. C., Renault, D., Fattal, E., Benech, H., Deverre, J. R. and Poncy, J. L. Simplified Structure of a New Model toDescribe Urinary Excretion of Plutonium after Systemic, Liver or Pulmonary Contamination of Rats Associated with Ca-DTPA Treatments. Radiat. Res. 171, 674–686 (2009).

This study validates, by targeted experiments, several modeling hypotheses for interpretation of urinary excretion of plutonium after Ca-DTPA treatments. Different formulations and doses of Ca-DTPA were administered to rats before or after systemic, liver or lung contamination with various chemical forms of plutonium. The biokinetics of plutonium was also characterized after i.v. injection of Pu-DTPA. Once formed, Pu-DTPA complexes are stable in most biological environments. Pu-DTPA present in circulating fluids is rapidly excreted in the urine, but 2–3% is retained, mainly in soft tissues, and is then excreted slowly in the urine after transfer to blood. Potentially, all intracellular monoatomic forms of plutonium could be decorporated after DTPA internalization involving slow urinary excretion of Pu-DTPA with half-lives varying from 2.5 to 6 days as a function of tissue retention. The ratio of fast to slow urinary excretion of Pu-DTPA depends on both plutonium contamination and Ca-DTPA treatment. Fast urinary excretion of Pu-DTPA corresponds to extracellular decorporation that occurs beyond a threshold of the free DTPA concentration in circulating fluids. Slow excretion corresponds mostly to intracellular decorporation and depends on the amount of intracellular DTPA. From these results, the structure of a simplified model is proposed for interpretation of data obtained with Ca-DTPA treatments after systemic, wound or pulmonary contamination by plutonium.

Cummings, R. J., Mitra, S., Foster, T. H. and Lord, E. M. Migration of Skin Dendritic Cells in Response to Radiation Exposure. Radiat. Res. 171, 687–697 (2009).

We describe an imaging assay that monitors the migration of two unique subsets of immune dendritic cells (DC), interstitial dendritic cells (iDC) and Langerhans cells (LC), found in the dermal and epidermal layers of skin, respectively. Using this assay, we study responses of these cells to ionizing radiation. Results obtained using whole-mount histology and fluorescence microscopy suggest that ionizing radiation triggered the migration of both major histocompatibility complex (MHC) class II iDC and Langerin LC in a dose- and time-dependent manner. Migration appeared to be limited by local administration of recombinant IL-12, a potent immunostimulatory cytokine known to induce DNA repair. Those findings were extended to an in vivo model by injecting fluorescently conjugated anti-MHC class II antibodies intradermally into the ears of live, anesthetized mice and visualizing the DC population in the same ear before and after radiation exposure using confocal microscopy.

Fu, Q., Berbée, M., Boerma, M., Wang, J., Schmid, H. A. and Hauer-Jensen, M. The Somatostatin Analog SOM230 (Pasireotide) Ameliorates Injury of the Intestinal Mucosa and Increases Survival after Total-Body Irradiation by Inhibiting Exocrine Pancreatic Secretion. Radiat. Res. 171, 698–707 (2009).

Somatostatin analogs ameliorate intestinal injury after localized irradiation. This study investigated whether SOM230, a novel, metabolically stable analog with broad receptor affinity, reduces intestinal injury and lethality in mice exposed to total-body irradiation (TBI). Male CD2F1 mice were exposed to 7–15 Gy TBI. Twice-daily administration of SOM230 (1, 4 or 10 mg/kg per day) or vehicle was started either 2 days before or 4 h after TBI and continued for either 14 or 21 days. Parameters of intestinal and hematopoietic radiation injury, bacterial translocation, and circulating cytokine levels were assessed. Animal survival was monitored for up to 30 days. SOM230 increased survival (P < 0.001) and prolonged survival time (P < 0.001) whether administration was initiated before or after TBI. There was no benefit from administration for 21 compared to 14 days. The survival benefit of SOM230 was completely reversed by co-administration of pancreatic enzymes (P  =  0.009). Consistent with the presumed non-cytoprotective mechanism of action, SOM230 did not influence hematopoietic injury or intestinal crypt lethality. However, SOM230 preserved mucosal surface area (P < 0.001) and reduced bacterial translocation in a dose-dependent manner (P < 0.001). Circulating IL-12 levels were reduced in SOM230-treated mice (P  =  0.007). No toxicity from SOM230 was observed. SOM230 enhances animal survival whether administration begins before or after TBI; i.e., it is effective both as a protector and as a mitigator. The mechanism likely involves reduction of intraluminal pancreatic enzymes. Because of its efficacy and favorable safety profile, SOM230 is a promising countermeasure against radiation and should undergo further development.

Lin, Y., Nagasawa, H., Peng, Y., Chuang, E. Y. and Bedford, J. S. Comparison of Several Radiation Effects in Human MCF10A Mammary Epithelial Cells Cultured as 2D Monolayers or 3D Acinar Stuctures in Matrigel. Radiat. Res. 171, 708–715 (2009).

It has been argued that the cell-cell and cell-matrix interaction networks in normal tissues are disrupted by radiation and that this largely controls many of the most important cellular radiation responses. This has led to the broader assertion that individual cells in normal tissue or a 3D normal-tissue-like culture will respond to radiation very differently than the same cells in a 2D monolayer culture. While many studies have shown that, in some cases, cell-cell contact in spheroids of transformed or tumor cell lines can alter radiation responses relative to those for the same cells in monolayer cultures, a question remains regarding the possible effect of the above-mentioned disruption of signaling networks that operate more specifically for cells in normal tissues or in a 3D tissue-like context. To test the generality of this notion, we used human MCF-10A cells, an immortalized mammary epithelial cell line that produces acinar structures in culture with many properties of human mammary ducts. We compared the dose responses for these cells in the 2D monolayer and in 3D ductal or acinar structures. The responses examined were reproductive cell death, induction of chromosomal aberrations, and the levels of γ-H2AX foci in cells after single acute γ-ray doses and immediately after 20 h of irradiation at a dose rate of 0.0017 Gy/min. We found no significant differences in the dose responses of these cells in 2D or 3D growth conditions. While this does not mean that such differences cannot occur in other situations, it does mean that they do not generally or necessarily occur.

Tsai, M-L., Chang, K-Y., Chiang, C-S., Shu, W-Y., Weng, T-C., Chen, C. R., Huang, C-L., Lin, H-K. and Hsu, I. C. UVB Radiation Induces Persistent Activation of Ribosome and Oxidative Phosphorylation Pathways. Radiat. Res. 171, 716–724 (2009).

Ultraviolet B (UVB) radiation has strong biological effects and modulates the expression of many genes. The major biological pathways affected by UVB radiation remain controversial. In this work, we used a loop-design microarray approach and applied rigorous statistical analyses to identify differentially regulated genes at 4, 8, 16 or 24 h after UVB irradiation. The most prominent biological categories in lists of differentially regulated gene sets were extracted by functional enrichment analysis. With this approach, we determined that genes participating in two prime cellular processes, the ribosome pathway and the oxidative phosphorylation pathway, were persistently activated after UVB irradiation. Mitochondrial activity assays confirmed increased activity for up to 24 h after UVB irradiation. These results suggest that the persistent activation of ribosome and oxidative phosphorylation pathways may have a key role in UVB-radiation-induced cellular responses. For the first time, the specific cellular pathways that respond to UVB radiation consistently and persistently can be delineated with confidence using a loop-design microarray approach and functional bioinformatics analysis. The results of this study offer further insight into UVB-radiation-induced stress responses.

Warters, R. L., Gaffney, D. K., Kramer, G. F., Martinez, J. D. and Cress A. E. Transient Phosphorylation of p53 Serine 376 as an Early Response to Ionizing Radiation. Radiat. Res. 171, 725–734 (2009).

In a previous paper we reported that the cytoplasmic sequestered p53 in cells of the SK-N-SH neuroblastoma cell line could be induced to translocate to the nucleus by exposure to ionizing radiation. We have extended these studies to determine the fate of p53 in HCT116 colorectal carcinoma cells where constitutive p53 protein resides in the nucleus. A continuous increase in the nuclear p53 protein was observed in irradiated cells beginning 1 h after irradiation that persisted for 8 h. Surprisingly, immunofluorescence microscopy revealed a transient, rapid and sensitive increase in a radiation-induced nuclear dephosphorylated p53 using antibody PAb421, which detects p53 when serine 376 is dephosphorylated. The PAb421 epitope was detectable after exposure to radiation doses as low as 0.5 cGy and was 10 to 20 times more sensitive compared to detection of p53 protein levels. The results are consistent with a radiation-induced, sensitive and rapid dephosphorylation of p53 at serine 376. The rapid increase in the nuclear PAb421 epitope was blocked by the protein serine phosphatase inhibitor calyculin A but was not blocked by the protein synthesis inhibitor cycloheximide, suggesting that serine 376 was dephosphorylated by protein serine phosphatase 1 or 2A acting on pre-existing p53 protein. The data suggest that dephosphorylation of serine 376 on constitutive nuclear p53 is a sensitive and early signaling event in the response of cells to DNA damage induced by ionizing radiation.

Sannino, A., Sarti, M., Reddy, S. B., Prihoda, T. J., Vijayalaxmi and Scarfì, M. R. Induction of Adaptive Response in Human Blood Lymphocytes Exposed to Radiofrequency Radiation. Radiat. Res. 171, 735–742 (2009).

The incidence of micronuclei was evaluated to assess the induction of an adaptive response to non-ionizing radiofrequency (RF) radiation in peripheral blood lymphocytes collected from five different human volunteers. After stimulation with phytohemagglutinin for 24 h, the cells were exposed to an adaptive dose of 900 MHz RF radiation used for mobile communications (at a peak specific absorption rate of 10 W/kg) for 20 h and then challenged with a single genotoxic dose of mitomycin C (100 ng/ml) at 48 h. Lymphocytes were collected at 72 h to examine the frequency of micronuclei in cytokinesis-blocked binucleated cells. Cells collected from four donors exhibited the induction of adaptive response (i.e., responders). Lymphocytes that were pre-exposed to 900 MHz RF radiation had a significantly decreased incidence of micronuclei induced by the challenge dose of mitomycin C compared to those that were not pre-exposed to 900 MHz RF radiation. These preliminary results suggested that the adaptive response can be induced in cells exposed to non-ionizing radiation. A similar phenomenon has been reported in cells as well as in animals exposed to ionizing radiation in several earlier studies. However, induction of adaptive response was not observed in the remaining donor (i.e., non-responder). The incidence of micronuclei induced by the challenge dose of mitomycin C was not significantly different between the cells that were pre-exposed and unexposed to 900 MHz RF radiation. Thus the overall data indicated the existence of heterogeneity in the induction of an adaptive response between individuals exposed to RF radiation and showed that the less time-consuming micronucleus assay can be used to determine whether an individual is a responder or non-responder.

Sannino, A., Di Costanzo, G., Brescia, F., Sarti, M., Zeni, O., Juutilainen, J. and Scarfì, M. R. Human Fibroblasts and 900 MHz Radiofrequency Radiation: Evaluation of DNA Damage after Exposure and Co-exposure to 3-Chloro-4-(dichloromethyl)-5-Hydroxy-2(5h)-furanone (MX). Radiat. Res. 171, 743–751 (2009).

The aim of this study was to investigate DNA damage in human dermal fibroblasts from a healthy subject and from a subject affected by Turner's syndrome that were exposed for 24 h to radiofrequency (RF) radiation at 900 MHz. The RF-radiation exposure was carried out alone or in combination with 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a well-known environmental mutagen and carcinogen produced during the chlorination of drinking water. Turner's syndrome fibroblasts were also exposed for a shorter time (1 h). A signal similar to that emitted by Global System for Mobile Communications (GSM) mobile phones was used at a specific absorption rate of 1 W/kg under strictly controlled conditions of temperature and dosimetry. To evaluate DNA damage after RF-radiation exposure alone, the alkaline comet assay and the cytokinesis-block micronucleus assay were used. In the combined-exposure experiments, MX was given at a concentration of 25 µM for 1 h immediately after the RF-radiation exposure, and the effects were evaluated by the alkaline comet assay. The results revealed no genotoxic and cytotoxic effects from RF radiation alone in either cell line. As expected, MX treatment induced an increase in DNA migration in the comet assay, but no enhancement of the MX-induced DNA damage was observed in the cells exposed to RF radiation.

George, K. A., Hada, M., Jackson, L. J., Elliott, T., Kawata, T., Pluth, J. M. and Cucinotta, F. A. Dose Response for c Rays and Iron Nuclei for Induction of Chromosomal Aberrations in Normal and Repair-Deficient Cell Lines. Radiat. Res. 171, 752–763 (2009).

We studied the effects of DNA double-strand break (DSB) repair deficiencies on chromosomal aberration frequency using low doses (<1 Gy) of γ rays and high-energy iron ions (LET  =  151 keV/µm). Chromosomal aberrations were measured using the fluorescence whole-chromosome painting technique. The cell lines included fibroblasts deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome) and gliomablastoma cells proficient in or lacking DNA-dependent protein kinase (DNA-PK) activity. The yields of both simple and complex chromosomal aberrations were increased in DSB repair-defective cells compared to normal cells; the increase was more than twofold higher for γ rays compared to iron nuclei. For γ-ray-induced aberrations, the ATM- and NBS-defective lines were found to have significantly larger quadratic components compared to normal fibroblasts for both simple and complex aberrations, while the linear dose–response term was significantly higher only for the NBS cells. For simple and complex aberrations induced by iron nuclei, regression models preferred purely linear and quadratic dose responses, respectively, for each cell line studied. RBEs were reduced relative to normal cells for all of the DSB repair-defective lines, with the DNA-PK-deficient cells found to have RBEs near unity. The large increase in the quadratic dose–response terms in the DSB repair-deficient cell lines points to the importance of the functions of ATM and NBS in chromatin modifications to facilitate correct DSB repair and to minimize aberration formation. The differences found between AT and NBS cells at lower doses suggest important questions about the applicability of observations of radiation sensitivity at high doses to low-dose exposures.

Elmore, E., Lao, X-Y., Kapadia, R. and Redpath, J. L. Threshold-Type Dose Response for Induction of Neoplastic Transformation by 1 GeV/nucleon Iron Ions. Radiat. Res. 171, 764ndash;770 (2009).

Neoplastic transformation of HeLa × skin fibroblast human hybrid cells by doses of 1 GeV/nucleon iron ions in the range 1 cGy to 1 Gy to exposed cultures has been examined. The data indicate a threshold-type dose–response curve with no increase in transformation frequency until doses above 20 cGy. At doses <10 cGy, not all exposed cells receive a direct traversal of an iron-ion track core, but all exposed cells receive up to several mGy of low-LET radiation associated with the δ-ray penumbra. It is proposed that the threshold-type response seen is a consequence of an adaptive response associated with the δ-ray exposure. For comparison purposes, the dose response for ¹³⁷Cs γ rays over the same dose range was examined using the same experimental procedure. As we have shown previously, the dose response for ¹³⁷Cs γ radiation was J-shaped. The iron ions were 1.5 to 1.7 times more biologically effective than the γ radiation over the dose range examined.

Yoon, A. J., Shen, J., Wu, H-C., Angelopoulos, C., Singer, R. S., Chen, R. and Santella, R. M. Expression of Activated Checkpoint Kinase 2 and Histone 2AX in Exfoliative Oral Cells after Exposure to Ionizing Radiation. Radiat. Res. 171, 771–775 (2009).

γ-H2AX (activated histone 2AX) and pChk2 (activated checkpoint kinase 2), which are DNA damage response molecules, are produced in irradiated cells and may be signature molecules of radiation exposure. We investigated their use as potential biomarkers to identify individuals exposed to ionizing radiation. We collected exfoliated oral epithelial cell samples from 100 healthy individuals undergoing routine dental radiographic examination (2.34 cGy) both before and after the radiograph using a non-invasive technique. The expression levels of pChk2 and γ-H2AX in oral cells were assessed by immunohistochemical assay. Both biomarkers showed statistically significant increases in levels of expression after the radiation exposure (P < 0.001). This suggests that pChk2 and γ-H2AX may serve as sensitive indicators of low-dose radiation exposure.