Radiotherapy, surgery and the chemotherapeutic agent temozolomide (TMZ) are frontline treatments for glioblastoma multiforme (GBM). However beneficial, GBM treatments nevertheless cause anxiety or depression in nearly 50% of patients. To further understand the basis of these neurological complications, we investigated the effects of combined radiotherapy and TMZ chemotherapy (combined treatment) on neurological impairments using a mouse model. Five weeks after combined treatment, mice displayed anxiety-like behaviors, and at 15 weeks both anxiety- and depression-like behaviors were observed. Relevant to the known roles of the serotonin axis in mood disorders, we found that 5HT1A serotonin receptor levels were decreased by ∼50% in the hippocampus at both early and late time points, and a 37% decrease in serotonin levels was observed at 15 weeks postirradiation. Furthermore, chronic treatment with the selective serotonin reuptake inhibitor fluoxetine was sufficient for reversing combined treatment-induced depression-like behaviors. Combined treatment also elicited a transient early increase in activated microglia in the hippocampus, suggesting therapy-induced neuroinflammation that subsided by 15 weeks. Together, the results of this study suggest that interventions targeting the serotonin axis may help ameliorate certain neurological side effects associated with the clinical management of GBM to improve the overall quality of life for cancer patients.

While radiosensitizing chemotherapy has improved survival for several types of cancer, current chemoradiation regimens remain ineffective for many patients and have substantial toxicities. Given the strong need for the development of novel radiosensitizers to further improve patient outcomes, the Radiation Research Program (RRP) and the Small Business Innovation Research (SBIR) in the National Cancer Institute (NCI) issued a Request for Proposals (RFP) through the NCI SBIR Development Center's contracts pathway. We sought to determine the research outcomes for the NCI SBIR Development Center's funded proposals for the development of radiosensitizers. We identified SBIR-funded contracts and grants for the development of radiosensitizers from 2009 to 2018 using the National Institutes of Health (NIH) Reporter database. Research outcomes of the NCI SBIR Development Center-funded proposals were determined using a comprehensive internet search. We searched PubMed, clinicaltrials.gov, company websites and google.com for research articles, abstracts and posters, clinical trials, press releases and other news, related to progress in the development of funded radiosensitizers. To protect the intellectual property of the investigators and small businesses, all information obtained and reported is publicly available. The SBIR Program has funded four contracts and 11 grants for the development of novel radiosensitizers. Two companies have received phase IIb bridge awards. Overall, 50% of companies (6/12) have successfully advanced their investigational drugs into prospective clinical trials in cancer patients, and all but one company are investigating their drug in combination with radiation therapy as described in the NCI SBIR Development Center proposal. To date, only one company has initiated a randomized trial of standard of care with or without their radiosensitizer. In conclusion, the NCI SBIR Development Center has funded the development of novel radiosensitizers leading to clinical trials of novel drugs in combination with radiation therapy. Continued follow-up is needed to determine if any of these novel radiosensitizers produce improved tumor control and/or overall survival.

Mitigation of total-body irradiation (TBI) in C57BL/6 mice by two drugs, which target apoptosis and necroptosis respectively, increases survival compared to one drug alone. Here we investigated whether the biomarker (signature)directed addition of a third anti-ferroptosis drug further mitigated TBI effects. C57BL/6NTac female mice (30–33 g) received 9.25 Gy TBI, and 24 h or later received JP4-039 (20 mg/kg), necrostatin-1 (1.65 mg/kg) and/or lipoxygenase-15 inhibitor (baicalein) (50 mg/kg) in single-, dual- or three-drug regimens. Some animals were sacrificed at days 0, 1, 2, 3, 4 or 7 postirradiation, while the majority in each group were maintained beyond 30 days. For those mice sacrificed at the early time points, femur bone marrow, intestine (ileum), lung and blood plasma were collected and analyzed for radiation-induced and mitigator-modified levels of 33 pro-inflammatory and stress response proteins. Each single mitigator administered [JP4-039 (24 h), necrostatin-1 (48 h) or baicalein (24 h)] improved survival at day 30 after TBI to 25% (P = 0.0432, 0.2816 or 0.1120, respectively) compared to 5% survival of 9.25 Gy TBI controls. Mice were administered the drug individually based on weight (mg/kg). Drug vehicles comprised 30% cyclodextrin for JP4-039 and baicalein, and 10% Cremphor-EL/10% ethanol/80% water for necrostatin-1; thus, dual-vehicle controls were also tested. The dual-drug combinations further enhanced survival: necrostatin-1 (delayed to 72 h) with baicalein 40% (P = 0.0359); JP4-039 with necrostatin-1 50% (P = 0.0062); and JP4-039 with baicalein 60% (P = 0.0064). The three-drug regimen, timed to signature directed evidence of onset after TBI of each death pathway in marrow and intestine, further increased the 30-day survival to 75% (P = 0.0002), and there was optimal normalization to preirradiation levels of inflammatory cytokine and stress response protein levels in plasma, intestine and marrow. In contrast, lung protein levels were minimally altered by 9.25 Gy TBI or mitigators over 7 days. Significantly, elevated intestinal proteins at day 7 after TBI were reduced by necrostatin-1-containing regimens; however, normalization of plasma protein levels at day 7 required the addition of JP4-039 and baicalein. These findings indicate that mitigator targeting to three distinct cell death pathways increases survival after TBI.

Findings from previous studies have suggested that the telomerase system is involved in radiation-induced genomic instability. In this study, we investigated the involvement of telomerase in the development and processing of chromosomal damage at different cell cycle stages after irradiation of human fibroblasts. Several response criteria were investigated, including cell survival, chromosomal damage (using the micronucleus assay), G₂-induced chromatid aberrations (using the conventional G₂ assay as well as a chemically-induced premature chromosome condensation assay) and DNA double-strand breaks (DSBs; using γ-H2AX, 53BP1 and Rad51) in an isogenic pair of cell lines: BJ human foreskin fibroblasts and BJ1-hTERT, a telomerase-immortalized BJ cell line. To distinguish among G₁, S and G₂ phase, cells were co-immunostained for CENP-F and cyclin A, which are tightly regulated proteins in the cell cycle. After X-ray irradiation at doses in the range of 0.1–6 Gy, the results showed that for cell survival and micronuclei induction, where the overall effect is dominated by the cells in G₁ and S phase, no difference was observed between the two cell types; in contrast, when radiation sensitivity at the G₂ stage of the cell cycle was analyzed, a significantly higher number of chromatid-type aberrations (breaks and exchanges), and higher levels of γ-H2AX and of Rad51 foci were observed for the BJ cells compared to the BJ1-hTERT cells. Therefore, it can be concluded that telomerase appears to be involved in DNA DSB repair processes, mainly in the G₂ phase. These data, taken overall, reinforce the notion that hTERT or other elements of the telomere/telomerase system may defend chromosome integrity in human fibroblasts by promoting repair in G₂ phase of the cell cycle.

Human embryonic brain development is highly sensitive to ionizing radiation. However, detailed information on the mechanisms of this sensitivity is not available due to limited experimental data. In this study, differentiation of human embryonic stem cells (hESCs) to neural lineages was used as a model for early embryonic brain development to assess the effect of exposure to low (17 mGy) and high (572 mGy) doses of radiation on gene expression. Transcriptomes were assessed using RNA sequencing during neural differentiation at three time points in control and irradiated samples. The first time point was when the cells were still pluripotent (day 0), the second time point was during the stage of embryoid body formation (day 6), and the third and final time point was during the stage of neural rosette formation (day 10). Analysis of the transcriptomes revealed neurodifferentiation in both the control and irradiated cells. Low-dose irradiation did not result in changes in gene expression at any of the time points, whereas high-dose irradiation resulted in downregulation of some major neurodifferentiation markers on days 6 and 10. Gene ontology analysis showed that pathways related to nervous system development, neurogenesis and generation of neurons were among the most affected. Expression of such key regulators of neuronal development as NEUROG1, ARX, ASCL1, RFX4 and INSM1 was reduced more than twofold. In conclusion, exposure to a 17 mGy low dose of radiation was well tolerated by hESCs while exposure to 572 mGy significantly affected their genetic reprogramming into neuronal lineages.

Stereotactic radiotherapy (SRT) is recommended for treatment of brain oligometastasis (BoM) in patients with controlled primary disease. Where contrast enhancement enlargement occurs during follow-up, distinguishing between radionecrosis and progression presents a critical challenge. Without pathological confirmation, decision-making may be inappropriate and delayed. Quantitative imaging features extracted from routinely performed examinations are of interest in potentially addressing this problem. We explored the added value of the radiomics method for the differential diagnosis of these two entities. Twenty patients who received SRT for BoM, from any primary location, were included (8 radionecrosis, 12 progressions, pathologically confirmed). We assessed the clinical relevance of 1,766 radiomics features, extracted using IBEX software, from the first T1-weighted postcontrast magnetic resonance imaging (MRI) after SRT showing a lesion modification. We evaluated seven feature-selection methods and 12 classification methods in terms of respective predictive performance. The classification accuracy was measured using Cohen's kappa after leave-one-out cross-validation. In this work, the best predictive power reached was a Cohen's kappa of 0.68 (overall accuracy of 85%), expressing a strong agreement between the algorithm prediction and the histological gold standard. Prediction accuracy was 75% for radionecrosis, and 91% for progression. The area under a curve reached 0.83 using a bagging algorithm trained with the chi-square score features set. These findings indicated that the radiomics method is able to discriminate radionecrosis from progression in an accurate, early and noninvasive way. This promising study is a proof of concept, preceding a larger prospective study for defining a robust model to support decision-making in BoM. In summary, distinguishing between radionecrosis and progression is challenging without pathology. We built a classification model based on imaging data and machine learning. Using this model, we were able predict progression and radionecrosis in, respectively, 91% and 75% of cases.

During fractionated radiotherapy, epithelial cell populations are thought to decrease initially, followed by accelerated repopulation to compensate cell loss. However, previous findings in skin with daily 1.1 Gy dose fractions indicate continued and increasing cell depletion. Here we investigated epidermal keratinocyte response with daily 2 Gy fractions as well as accelerated and hypofractionation. Epidermal interfollicular melanocytes were also assessed. Skin-punch biopsies were collected from breast cancer patients before, during and after mastectomy radiotherapy to the thoracic wall with daily 2 Gy fractions for 5 weeks. In addition, 2.4 Gy radiotherapy four times per week and 4 Gy fractions twice per week for 5 weeks, and two times 2 Gy daily for 2.5 weeks, were used. Basal keratinocyte density of the interfollicular epidermis was determined and immunostainings of keratinocytes for DNA double-strand break (DSB) foci, growth arrest, apoptosis and mitosis were quantified. In addition, interfollicular melanocytes were counted. Initially minimal keratinocyte loss was observed followed by pronounced depletion during the second half of treatment and full recovery at 2 weeks post treatment. DSB foci per cell peaked towards the end of treatment. p21-stained cell counts increased during radiotherapy, especially the second half. Apoptotic frequency was low throughout radiotherapy but increased at treatment end. Mitotic cell count was significantly suppressed throughout radiotherapy and did not recover during weekend treatment gaps, but increased more than threefold compared to unexposed skin 2 weeks post-radiotherapy. The number of melanocytes remained constant over the study period. Germinal keratinocyte loss rate increased gradually during daily 2 Gy fractions for 5 weeks, and similarly for hypofractionation. DSB foci number after 2 Gy irradiation revealed an initial radioresistance followed by increasing radiosensitivity. Growth arrest mediated by p21 strongly suggests that cells within or recruited into the cell cycle during treatment are at high risk of loss and do not contribute significantly to repopulation. It is possible that quiescent (G₀) cells at treatment completion accounted for the accelerated post-treatment repopulation. Recent knowledge of epidermal tissue regeneration and cell cycle progression during genotoxic and mitogen stress allows for a credible explanation of the current finding. Melanocytes were radioresistant regarding cell depletion.

In this article, we offer a look inside our prototype compact X-ray tube by reporting on our findings when we experimentally studied it. We studied the prototype experimentally to characterize its primary components, i.e., carbon nanotube (CNT)-based cold cathode, electrostatic lens and transmission-type anode, and to validate our previous simulation studies. We characterized the CNT-based cold cathode by studying the relationship between the electron emission current and its control parameter, electron extraction voltage. This relationship, commonly known as the current-voltage characteristic, showed an exponential-like nature that is expected from the Fowler-Nordheim model for field emission. Next, we characterized the electrostatic lens by studying the effects of lens voltage on the focal spot size. Their relationship showed a “V” trend and corroborated that we can control the focal spot size by controlling the lens voltage. We then characterized the transmission-type anode of the prototype by studying its output X-ray energy spectra at different anode voltages. We could control the highest and the mean X-ray energies generated from the transmission-type anode using the anode voltage. For the same anode voltage and aluminum filtration, when we compared the Xray energy spectrum generated from the transmission-type anode with that of the conventional reflection-type anode, we observed that the two energy spectra agreed with each other.