Histone H2AX Phosphorylation as a Predictor of Radiosensitivity and Target for Radiotherapy

Two distinct subpopulations of marginal zone B cells exhibit differential antibody-producing capacities and radioresistance

Marginal zone (MZ) B cells, which are splenic innate-like B cells that rapidly secrete antibodies (Abs) against blood-borne pathogens, are composed of heterogeneous subpopulations. Here, we showed that MZ B cells can be divided into two distinct subpopulations according to their CD80 expression levels. CD80high MZ B cells exhibited greater Ab-producing, proliferative, and IL-10-secreting capacities than did CD80low MZ B cells. Notably, CD80high MZ B cells survived 2-Gy whole-body irradiation, whereas CD80low MZ B cells were depleted by irradiation and then repleted with one month after irradiation. Depletion of CD80low MZ B cells led to accelerated development of type II collagen (CII)-induced arthritis upon immunization with bovine CII. CD80high MZ B cells exhibited higher expression of genes involved in proliferation, plasma cell differentiation, and the antioxidant response. CD80high MZ B cells expressed more autoreactive B cell receptors (BCRs) that recognized double-stranded DNA or CII, expressed more immunoglobulin heavy chain sequences with shorter complementarity-determining region 3 sequences, and included more clonotypes with no N-nucleotides or with B-1a BCR sequences than CD80low MZ B cells. Adoptive transfer experiments showed that CD21+CD23+ transitional 2 MZ precursors preferentially generated CD80low MZ B cells and that a proportion of CD80low MZ B cells were converted into CD80high MZ B cells; in contrast, CD80high MZ B cells stably remained CD80high MZ B cells. In summary, MZ B cells can be divided into two subpopulations according to their CD80 expression levels, Ab-producing capacity, radioresistance, and autoreactivity, and these findings may suggest a hierarchical composition of MZ B cells with differential stability and BCR specificity.

MiR-630 Promotes Radioresistance by Induction of Anti-Apoptotic Effect via Nrf2-GPX2 Molecular Axis in Head-Neck Cancer

Head and neck cancer (HNC) ranks among the top ten prevalent cancers worldwide. Radiotherapy stands as a pivotal treatment component for HNC; however, radioresistance in cancerous cells often leads to local recurrence, becoming a substantial factor in treatment failure. MicroRNAs (miRNAs) are compact, non-coding RNAs that regulate gene expression by targeting mRNAs to inhibit protein translation. Although several studies have indicated that the dysregulation of miRNAs is intricately linked with malignant transformation, understanding this molecular family's role in radioresistance remains limited. This study determined the role of miR-630 in regulating radiosensitivity in HNC. We discovered that miR-630 functions as an oncomiR, marked by its overexpression in HNC patients, correlating with a poorer prognosis. We further delineated the malignant function of miR-630 in HNC cells. While it had a minimal impact on cell growth, the miR-630 contributed to radioresistance in HNC cells. This result was supported by decreased cellular apoptosis and caspase enzyme activities. Moreover, miR-630 overexpression mitigated irradiation-induced DNA damage, evidenced by the reduced levels of the γ-H2AX histone protein, a marker for double-strand DNA breaks. Mechanistically, the overexpression of miR-630 decreased the cellular ROS levels and initiated Nrf2 transcriptional activity, resulting in the upregulation of the antioxidant enzyme GPX2. Thus, this study elucidates that miR-630 augments radioresistance by inducing an anti-apoptotic effect via the Nrf2-GPX2 molecular axis in HNC. The modulation of miR-630 may serve as a novel radiosensitizing target for HNC.

Evaluation of the relationship between γ-H2AX biomarker levels and dose received after radiation exposure in abdominal-pelvic and chest CT scans

Background

As one of the most informative diagnostic radiation instruments, computed tomography (CT) has seen considerable improvement since its implementation in the 1970s; however, the possibility of low-dose radiation risk after CT procedures is still challenging and little is known about the biological effects of CT exposure on patients. As a result, this research aimed to look at the biological and cytogenetic effects of low-dose abdominal-pelvic and chest CT scans on adults, focusing on the number of γ-H2AX foci formation.

Materials and Methods

Blood tests were taken before and 10 min after CT exams on patients aged 25-55 who were undergoing abdominal-pelvic and chest CT exams with very low-ionizing radiation exposure (TLD doses of 15.67-63.45 mGy). Blood lymphocytes that had been isolated, fixed, and stained were dyed with γ-H2AX antibodies. Finally, the percentage of phosphorylation of histone H2AX as an indicator of double-strand breaks was determined using a cytometry technique.

Results

Our findings showed that after CT examination, the mean value of γ-H2AX foci in patients increased (P < 0.0001). A statistically significant correlation between dose radiation and the number of γ-H2AX foci was also found (P = 0.047, r = 0.4731). The current study also found a pattern of elevated γ-H2AX foci in patients over 40 years of age relative to younger patients.

Conclusion

A Significant activation of γ-H2AX foci was found in lymphocytes of peripheral blood samples of patients after CT compared to before CT scan. This increase in γ-H2AX foci levels in blood cells may be a useful quantitative biomarker of low-level radiation exposure in humans.

Improving the efficacy of combined radiotherapy and immunotherapy: focusing on the effects of radiosensitivity

Cancer treatment is gradually entering an era of precision, with multitude studies in gene testing and immunotherapy. Tumor cells can be recognized and eliminated by the immune system through the expression of tumor-associated antigens, but when the cancer escapes or otherwise suppresses immunity, the balance between cancer cell proliferation and immune-induced cancer cell killing may be interrupted, resulting in tumor proliferation and progression. There has been significant attention to combining conventional cancer therapies (i.e., radiotherapy) with immunotherapy as opposed to treatment alone. The combination of radio-immunotherapy has been demonstrated in both basic research and clinical trials to provide more effective anti-tumor responses. However, the absolute benefits of radio-immunotherapy are dependent on individual characteristics and not all patients can benefit from radio-immunotherapy. At present, there are numerous articles about exploring the optimal models for combination radio-immunotherapy, but the factors affecting the efficacy of the combination, especially with regard to radiosensitivity remain inconclusive. Radiosensitivity is a measure of the response of cells, tissues, or individuals to ionizing radiation, and various studies have shown that the radiosensitivity index (RSI) will be a potential biomarker for predicting the efficacy of combination radio-immunotherapy. The purpose of this review is to focus on the factors that influence and predict the radiosensitivity of tumor cells, and to evaluate the impact and predictive significance of radiosensitivity on the efficacy of radio-immunotherapy combination.

4-vinylcyclohexene diepoxide induces apoptosis by excessive reactive oxygen species and DNA damage in human ovarian granulosa cells

4-Vinylcyclohexene diepoxide (VCD) is a hazardous industrial material which is widely used in the production of fragrances, rubber tires, antioxidants, pesticides, flame retardants and plasticizers. Previous studies have shown that exposure to VCD damages the female reproductive system, but the effects and mechanisms of VCD exposure on human granulosa cells are not reported. In this study, we used a human granulosa cell line (SVOG) to explore the effects of VCD exposure and found that VCD exposure had toxic effects on SVOG cells in vitro. VCD exposure led to excessive accumulation of intracellular ROS, caused DNA damage in cells, altered the expression of some key genes related with apoptosis and oxidative stress, and ultimately inhibited the proliferative capacity of granulosa cells, resulting in increased apoptosis. Overall, our findings provide solid evidence showing that VCD exposure produces severe damage to human granulosa cells, which is helpful for understanding the reproductive toxicity of VCD and etiology of infertility.

Immunohistochemical Pattern of Histone H2A Variant Expression in an Experimental Model of Ischemia-Reperfusion-Induced Acute Kidney Injury

Ischemia-reperfusion injury (IRI) is a frequent cause of AKI, resulting in vasoconstriction, cellular dysfunction, inflammation and the induction of oxidative stress. DNA damage, including physical DNA strand breaks, is also a potential consequence of renal IRI. The histone H2A variants, primary H2AX and H2AZ participate in DNA damage response pathways to promote genome stability. The aim of this study was to evaluate the immunohistochemical pattern of histone H2A variants' (H2AX, γH2AX(S139), H2AXY142ph and H2AZ) expression in an experimental model of ischemia-reperfusion-induced acute kidney injury in spontaneously hypertensive rats. Comparing the immunohistochemical nuclear expression of γH2AX(S139) and H2AXY142ph in AKI, we observed that there is an inverse ratio of these two histone H2AX variants. If we follow different regions from the subcapsular structures to the medulla, there is an increasing extent gradient in the nuclear expression of H2AXY142ph, accompanied by a decreasing nuclear expression of γH2AX. In addition, we observed that different structures dominated when γH2AX and H2AXY142ph expression levels were compared. γH2AX was expressed only in the proximal tubule, with the exception of when they were dilated. In the medulla, H2AXY142ph is predominantly expressed in the loop of Henle and the collecting ducts. Our results show moderate sporadic nuclear H2AZ expression mainly in the cells of the distal tubules and the collecting ducts that were surrounded by dilated tubules with PAS (periodic acid-Schiff stain)-positive casts. These findings may indicate the degree of DNA damage, followed by postischemic AKI, with potential clinical and prognostic implications regarding this condition.

Characterization of Intrinsic Radiation Sensitivity in a Diverse Panel of Normal, Cancerous and CRISPR-Modified Cell Lines

Intrinsic radiosensitivity is a major determinant of radiation response. Despite the extensive amount of radiobiological data available, variability among different studies makes it very difficult to produce high-quality radiosensitivity biomarkers or predictive models. Here, we characterize a panel of 27 human cell lines, including those derived from lung cancer, prostate cancer, and normal tissues. In addition, we used CRISPR-Cas9 to generate a panel of lines with known DNA repair defects. These cells were characterised by measuring a range of biological features, including the induction and repair of DNA double-strand breaks (DSBs), cell cycle distribution, ploidy, and clonogenic survival following X-ray irradiation. These results offer a robust dataset without inter-experimental variabilities for model development. In addition, we used these results to explore correlations between potential determinants of radiosensitivity. There was a wide variation in the intrinsic radiosensitivity of cell lines, with cell line Mean Inactivation Doses (MID) ranging from 1.3 to 3.4 Gy for cell lines, and as low as 0.65 Gy in Lig4^-/- cells. Similar substantial variability was seen in the other parameters, including baseline DNA damage, plating efficiency, and ploidy. In the CRISPR-modified cell lines, residual DSBs were good predictors of cell survival (R² = 0.78, p = 0.009), as were induced levels of DSBs (R² = 0.61, p = 0.01). However, amongst the normal and cancerous cells, none of the measured parameters correlated strongly with MID (R² < 0.45), and the only metrics with statistically significant associations are plating efficiency (R² = 0.31, p = 0.01) and percentage of cell in S phase (R² = 0.37, p = 0.005). While these data provide a valuable dataset for the modelling of radiobiological responses, the differences in the predictive power of residual DSBs between CRISPR-modified and other subgroups suggest that genetic alterations in other pathways, such as proliferation and metabolism, may have a greater impact on cellular radiation response. These pathways are often neglected in response modelling and should be considered in the future.

Investigation of mRNA Expression Levels of Tip60 and Related DNA Repair Genes in Molecular Subtypes of Breast Cancer

INTRODUCTION

Studies in breast cancer (BC) have been shown that many tumor cells carry mutations that disrupt the DNA damage response mechanism. In eukaryotic cells, the overexpression or deprivation of DSBs repair genes is linked closely to a higher risk of cancer.

PATIENTS AND METHODS

In this study, mRNA expression levels of some genes, such as Tip60, ATM, p53, CHK2, BRCA1, H2AX, which are associated with DNA damage repair, were measured using RT-PCR method in tumor and matched-normal tissues of 58 patients with BC.

RESULTS

According to the study results, 55% in Tip60, 59% in ATM, 57% in BRCA1, 48% in H2AX, 66% in CHK2, and 43% in p53 decreased in tumor tissue of patients compared to the matched normal tissue. When evaluated according to molecular subtypes, expression of all genes in the pathway was found significantly higher in normal tissues than in tumor tissues especially in Luminal B and Luminal B+HER2 groups. One of the most important results of the study is that CHK2 mRNA expressions in normal tissues were higher than tumor tissue in 90% of patients in Luminal B and Luminal B-HER2 + groups. This is the first study showing DNA repair genes' expressions in molecular subtypes of breast cancer. In general, the decrease in the expression of DNA damage repair genes in tumor tissue indicates that these genes may have a role in the development of BC. Our study results also suggest that CHK2 may be a candidate marker in the molecular classification of breast cancer.

Synergetic effect of high dose rate radiations (10× FFF/2400 MU/min/10 MV x-rays) and paclitaxel selectively eliminates melanoma cells

BACKGROUND

Melanoma is one of the most aggressive cancers, with 1.6% of total cancer deaths in the United States. In recent years treatment options for metastatic melanoma have been improved by the FDA approval of new therapeutic agents. However, these inhibitors-based therapies are non-specific and have severe toxicities, including hyperkeratosis, photosensitivity, hepatitis, arthralgia, and fatigue.

AIMS

The aim of this study is to determine the synthetic lethal effect (paclitaxel and radiations) on melanoma cells and reduce the total radiation doses by increasing the dose rates up to 2400 MU/min.

METHODS AND RESULTS

We previously reported a radiation treatment (10 MV x-rays, 10X-FFF, dose rate 2400MU/min, low total dose 0.5 Gy) that kills melanoma cells with 80% survival of normal HEM in vitro. In this study, we extended the radiation cycle up to four and included paclitaxel treatment to study the synthetic lethal effect on melanoma and two other normal primary cells, HDF and HEK. Cells were treated with paclitaxel prior to the radiation at a dose rate of 400 and 2400 MU/min with a total radiation dose of only 0.5 Gy. Mitochondrial respiration assay, DNA damage assay, and colony formation assays were performed to study apoptosis and cell death induction. Four days of consequent radiation treatment with paclitaxel significantly reduces the survival of melanoma cells by inducing apoptosis and mitochondrial damage. After treatment, excessive DNA damage in melanoma cells leads to an increase in the expression of pro-apoptotic genes (Caspase-3) and a decrease in the expression of DNA repair gene (PARP1) and anti-apoptotic gene (Bcl-2) to activate the apoptosis pathway. The combination of paclitaxel and radiation reduces the survival of melanoma cells colonies compared to radiation alone.

CONCLUSION

Our study indicates that radiations with paclitaxel have a potential synthetic lethal effect on melanoma cells and can be developed as a melanoma therapy without toxicities or harmful effects on normal primary skin cells.

Gut microbiota-mediated nucleotide synthesis attenuates the response to neoadjuvant chemoradiotherapy in rectal cancer

Preoperative neoadjuvant chemoradiotherapy (nCRT) is a standard treatment for locally advanced rectal cancer (LARC) patients, yet little is known about the mediators underlying the heterogeneous patient response. In this longitudinal study, we performed 16S rRNA sequencing on 353 fecal specimens and find reduced microbial diversity after nCRT. Multi-omics data integration reveals that Bacteroides vulgatus-mediated nucleotide biosynthesis associates with nCRT resistance in LARC patients, and nonresponsive tumors are characterized by the upregulation of genes related to DNA repair and nucleoside transport. Nucleosides supplementation or B. vulgatus gavage protects cancer cells from the 5-fluorouracil or irradiation treatment. An analysis of 2,205 serum samples from 735 patients suggests that uric acid is a potential prognosis marker for LARC patients receiving nCRT. Our data unravel the role of intestinal microbiota-mediated nucleotide biosynthesis in the response of rectal tumors to nCRT, and highlight the importance of deciphering the cross-talk between cancer cells and gut microorganisms during cancer therapies.

Generation and Characterization of an Isogenic Cell Line Model of Radioresistant Esophageal Adenocarcinoma

Radiation therapy is a cornerstone of cancer treatment worldwide. Unfortunately, in many cases, it does not control tumor growth, and many tumors display treatment resistance. The molecular pathways leading to treatment resistance in cancer have been subject to research for many years. Isogenic cell lines with divergent radiosensitivities are an extremely useful tool to study the molecular mechanisms that underpin radioresistance in cancer research, as they reduce the genetic variation that is present in patient samples and cell lines of different origin, thus allowing the elucidation of molecular determinants of radioresponse. Here, we describe the process of generating an in vitro isogenic model of radioresistant esophageal adenocarcinoma by chronic irradiation of esophageal adenocarcinoma cells with clinically relevant doses of X-ray radiation. We also characterize cell cycle, apoptosis, reactive oxygen species (ROS) production, DNA damage and repair in this model to investigate the underlying molecular mechanisms of radioresistance in esophageal adenocarcinoma.

JNJ-64619178 radiosensitizes and suppresses fractionated ionizing radiation-induced neuroendocrine differentiation (NED) in prostate cancer

Background

Radiation therapy (RT) is a standard treatment regimen for locally advanced prostate cancer; however, its failure results in tumor recurrence, metastasis, and cancer-related death. The recurrence of cancer after radiotherapy is one of the major challenges in prostate cancer treatment. Despite overall cure rate of 93.3% initially, prostate cancer relapse in 20-30% patients after radiation therapy. Cancer cells acquire radioresistance upon fractionated ionizing radiation (FIR) treatment, eventually undergo neuroendocrine differentiation (NED) and transform into neuroendocrine-like cells, a mechanism involved in acquiring resistance to radiation therapy. Radiosensitizers are agents that inhibit the repair of radiation-induced DNA damage. Protein arginine methyltransferase 5 (PRMT5) gets upregulated upon ionizing radiation treatment and epigenetically activates DNA damage repair genes in prostate cancer cells. In this study, we targeted PRMT5 with JNJ-64619178 and assessed its effect on DNA damage repair gene activation, radiosensitization, and FIR-induced NED in prostate cancer.

Methods

γH2AX foci analysis was performed to evaluate the DNA damage repair after radiation therapy. RT-qPCR and western blot were carried out to analyze the expression of DNA damage repair genes. Clonogenic assay was conducted to find out the surviving fraction after radiation therapy. NED was targeted with JNJ-64619178 in androgen receptor (AR) positive and negative prostate cancer cells undergoing FIR treatment.

Results

JNJ-64619178 inhibits DNA damage repair in prostate cancer cells independent of their AR status. JNJ-64619178 impairs the repair of ionizing radiation-induced damaged DNA by transcriptionally inhibiting the DNA damage repair gene expression and radiosensitizes prostate, glioblastoma and lung cancer cell line. It targets NED induced by FIR in prostate cancer cells.

Conclusion

JNJ-64619178 can radiosensitize and suppress NED induced by FIR in prostate cancer cells and can be a potential radiosensitizer for prostate cancer treatment.

Radioresistance Mechanisms in Prostate Cancer Cell Lines Surviving Ultra-Hypo-Fractionated EBRT: Implications and Possible Clinical Applications

The use of a higher dose per fraction to overcome the high radioresistance of prostate cancer cells has been unsuccessfully proposed. Herein, we present PC3 and DU-145, castration-resistant prostate cancer cell lines that survived a clinically used ultra-higher dose per fraction, namely, radioresistant PC3 and DU-145 cells (PC3RR and DU-145RR). Compared to PC3, PC3RR showed a higher level of aggressive behaviour, with enhanced clonogenic potential, DNA damage repair, migration ability and cancer stem cell features. Furthermore, compared to PC3, PC3RR more efficiently survived further radiation by increasing proliferation and down-regulating pro-apoptotic proteins. No significant changes of the above parameters were described in DU-145RR, suggesting that different prostate cancer cell lines that survive ultra-higher dose per fraction do not display the same grade of aggressive phenotype. Furthermore, both PC3RR and DU-145RR increased antioxidant enzymes and mesenchymal markers. Our data suggest that different molecular mechanisms could be potential targets for future treatments plans based on sequential strategies and synergistic effects of different modalities, possibly in a patient-tailored fashion. Moreover, PC3RR cells displayed an increase in specific markers involved in bone remodeling, indicating that radiotherapy selects a PC3 population capable of migrating to secondary metastatic sites. Finally, PC3RR cells showed a better sensitivity to Docetaxel as compared to native PC3 cells. This suggests that a subset of patients with castration-resistant metastatic disease could benefit from upfront Docetaxel treatment after the failure of radiotherapy.

CD146 interaction with integrin β1 activates LATS1-YAP signaling and induces radiation-resistance in breast cancer cells

Radiotherapy is an indispensable modality in comprehensive treatment of breast cancer. However, inherent or acquired radiation resistance of tumors compromises the efficacy of radiotherapy. Herein, we found that CD146, a unique epithelial-to-mesenchymal transition (EMT) inducer particularly highly expressed in triple-negative breast cancer (TNBC), is dramatically induced by ionizing irradiation. Further study demonstrates that CD146 promotes tumor cell radioresistance in vitro and in vivo. Specifically, we report the underlying mechanism that CD146 activates YAP protein, and drives its relocation from plasma to nucleus by regulating LATS1, and promoting abnormal DNA damage repair, as well as inducing EMT and stemness. Moreover, CD146 can form a novel co-receptor complex with integrin β1 and induces radiation-resistance in breast cancer. Dual inhibition of CD146 and integrin β1 activity had a stronger inhibitory effect on breast cancer tumor growth and synergistically increased their sensitivity to radiotherapy. This study identifies a unique function of CD146 implicates with integrin β1 and YAP signaling, contributing to radiation resistance. Targeted therapy against CD146 or inhibition of integrin β1 is a potential strategy to overcome radiotherapeutic resistance of breast cancer.

Tea polyphenols alleviate the adverse effects of diabetes on oocyte quality

Maternal diabetes mellitus reduces oocyte quality, such as abnormalities of spindle assembly and chromosome segregation, mitochondrial dysfunction, decrease of fertilization rate, increase of ROS, and so on. So, it is important to research how to restore the decreased oocyte quality induced by maternal diabetes mellitus. Polyphenols are the most abundant bioactive components of green tea. It is reported that tea polyphenols have many health functions, for instance anti-oxidation, anti-inflammation, anti-obesity, and anti-diabetes. Thus, we hypothesize that tea polyphenols may play a crucial role in alleviating adverse effects of diabetes on oocyte quality. In the present study, we researched the effects of tea polyphenols on diabetic oocyte maturation in vitro. Compared with the control, oocytes from diabetic mice displayed a lower maturation rate and a higher frequency of spindle defects and chromosome misalignment. However, tea polyphenols significantly increased the oocyte maturation rate, and reduced the incidence of abnormal spindle assembly and chromosome segregation. Tea polyphenols also obviously decreased the reactive oxygen species (ROS) levels in diabetic oocytes, and increased the expression of antioxidant genes (Sod1 and Sod2). Abnormal mitochondrial membrane potential was also alleviated in diabetic oocytes, and the expression of genes regulating mitochondrial fusion (Opa1, Mfn1 and Mfn2) and fission (Drp1) was significantly increased while tea polyphenols were added. Meanwhile, tea polyphenols reduced DNA damage in diabetic oocytes which may be mediated by the increased expression of Rad51, related to DNA damage repair. Our results suggest that tea polyphenols would, at least partially, restore the adverse effects of diabetes mellitus on oocyte quality.

Radiosensitization of PC3 Prostate Cancer Cells by 5-Thiocyanato-2'-deoxyuridine

Simple Summary

Radiation therapy is one of the main treatments for cancer. However, the success of treatment by radiation therapy is largely dependent on tumor radiosensitivity. To improve therapeutic outcomes, radiation therapy should be combined with the use of a radiosensitizer which enables irradiation at lower doses with higher efficacies. 5-Thiocyanato-2′-deoxyuridine has been reported as a potential radiosensitizer of DNA damage based on advanced radiation chemical studies. In this paper, for the first time, we demonstrate the radiosensitizing properties of this modified nucleoside at the cellular level. The tested analogue increases the sensitivity of prostate cancer cells to ionizing radiation which is, at least partially, related to an increase in the number of DNA double-strand breaks and cell cycle regulation.

Abstract

Purpose: The radiosensitizing properties of uracil analogs modified in the C5 position are very interesting in the context of their effectiveness and safety in radiation therapy. Recently, radiation chemical studies have confirmed that 5-thiocyanato-2′-deoxyuridine (SCNdU) undergoes dissociation induced by an excess electron attachment and established this nucleoside as a potential radiosensitizer. In this paper, we verify the sensitizing properties of SCNdU at the cellular level and prove that it can effectively enhance ionizing radiation-induced cellular death. Methods and Materials: Prostate cancer cells were treated with SCNdU and irradiated with X rays. The cytotoxicity of SCNdU was determined by MTT test. Cell proliferation was assessed using a clonogenic assay. Cell cycle analyses, DNA damage, and cell death analyses were performed by flow cytometry. Results: SCNdU treatment significantly suppressed the proliferation and increased the radiosensitivity of prostate cancer cells. The radiosensitizing effect expressed by the dose enhancement factor is equal to 1.69. Simultaneous exposure of cells to SCNdU and radiation causes an increase in the fraction of the most radiosensitive G2/M phase, enhancement of the histone H2A.X phosphorylation level, and apoptosis induction. Finally, SCNdU turned out to be marginally cytotoxic in the absence of ionizing radiation. Conclusions: Our findings indicate that SCNdU treatment enhances the radiosensitivity of prostate cancer cells in a manner associated with the cell cycle regulation, double strand formation, and a slight induction of apoptosis.

BPIFA2 as a Novel Early Biomarker to Identify Fatal Radiation Injury After Radiation Exposure

Background

Current dosimeters cannot cope with the two tasks of medical rescue in the early stage of nuclear accident, the accurate determination of radiation exposure and the identification of patients with fatal radiation injury. As radiation can cause alterations in serum components, it is feasible to develop biomarkers for radiation injury from serum. This study aims to investigate whether serum BPIFA2 could be used as a potential biomarker of predicting fatal radiation injury in the early stage after nuclear accident.

Methods

A rabbit anti-mouse BPIFA2 polyclonal antibody was prepared to detect the expression of BPIFA2. C57BL/6J female mice were exposed to total body radiation (TBI) at different dose and Partial body radiation (PBI) at lethal dose to detect the dynamic changes of BPIFA2 in serum at different time points after irradiation by Western blot assay.

Results

BPIFA2 in mice serum were significantly increased at 1–12 h post-irradiation at .5–10 Gy, and increased again significantly at 3 d after 10 Gy irradiation with associated with mortality closely. It also increased rapidly after PBI and was closely related to injury degree, regardless whether the salivary glands were irradiated.

Conclusions

The increase of serum BPIFA2 is a novel early biomarker not only for identifying radiation exposure, but also for fatal radiation injury playing a vital role in rational use of medical resources, and greater efficiency of medical treatment to minimize casualties.

Analysis of Ionizing Radiation Induced DNA Damage by Superresolution dSTORM Microscopy

The quantitative detection of radiation caused DNA double-strand breaks (DSB) by immunostained γ-H2AX foci using direct stochastic optical reconstruction microscopy (dSTORM) provides a deeper insight into the DNA repair process at nanoscale in a time-dependent manner. Glioblastoma (U251) cells were irradiated with 250 keV X-ray at 0, 2, 5, 8 Gy dose levels. Cell cycle phase distribution and apoptosis of U251 cells upon irradiation was assayed by flow cytometry. We studied the density, topology and volume of the γ-H2AX foci with 3D confocal microscopy and the dSTORM superresolution method. A pronounced increase in γ-H2AX foci and cluster density was detected by 3D confocal microscopy after 2 Gy, at 30 min postirradiation, but both returned to the control level at 24 h. Meanwhile, at 24 h a considerable amount of residual foci could be measured from 5 Gy, which returned to the normal level 48 h later. The dSTORM based γ-H2AX analysis revealed that the micron-sized γ-H2AX foci are composed of distinct smaller units with a few tens of nanometers. The density of these clusters, the epitope number and the dynamics of γ-H2AX foci loss could be analyzed. Our findings suggest a discrete level of repair enzyme capacity and the restart of the repair process for the residual DSBs, even beyond 24 h. The dSTORM superresolution technique provides a higher precision over 3D confocal microscopy to study radiation induced γ-H2AX foci and molecular rearrangements during the repair process, opening a novel perspective for radiation research.

H2A.X Phosphorylation in Oxidative Stress and Risk Assessment in Plasma Medicine

At serine₁₃₉-phosphorylated gamma histone H2A.X (γH2A.X) has been established over the decades as sensitive evidence of radiation-induced DNA damage, especially DNA double-strand breaks (DSBs) in radiation biology. Therefore, γH2A.X has been considered a suitable marker for biomedical applications and a general indicator of direct DNA damage with other therapeutic agents, such as cold physical plasma. Medical plasma technology generates a partially ionized gas releasing a plethora of reactive oxygen and nitrogen species (ROS) simultaneously that have been used for therapeutic purposes such as wound healing and cancer treatment. The quantification of γH2A.X as a surrogate parameter of direct DNA damage has often been used to assess genotoxicity in plasma-treated cells, whereas no sustainable mutagenic potential of the medical plasma treatment could be identified despite H2A.X phosphorylation. However, phosphorylated H2A.X occurs during apoptosis, which is associated with exposure to cold plasma and ROS. This review summarizes the current understanding of γH2A.X induction and function in oxidative stress in general and plasma medicine in particular. Due to the progress towards understanding the mechanisms of H2A.X phosphorylation in the absence of DSB and ROS, observations of γH2A.X in medical fields should be carefully interpreted.

DNAPK Inhibition Preferentially Compromises the Repair of Radiation-induced DNA Double-strand Breaks in Chronically Hypoxic Tumor Cells in Xenograft Models

Radiation-induced DNA double-strand breaks (DSBs) can be repaired by homologous recombination (HR) and nonhomologous end joining (NHEJ). Recently, it has been found that chronic tumor hypoxia compromises HR repair of DNA DSBs but activates the NHEJ protein DNAPK. We therefore hypothesized that inhibition of DNAPK can preferentially potentiate the sensitivity of chronically hypoxic cancer cells to radiation through contextual synthetic lethality in vivo In this study, we investigated the impact of DNAPK inhibition by a novel selective DNAPK inhibitor, NU5455, on the repair of radiation-induced DNA DSBs in chronically hypoxic and nonhypoxic cells across a range of xenograft models. We found that NU5455 inhibited DSB repair following radiation in both chronically hypoxic and nonhypoxic tumor cells. Most importantly, the inhibitory effect was more pronounced in chronically hypoxic tumor cells than in nonhypoxic tumor cells. This is the first in vivo study to indicate that DNAPK inhibition may preferentially sensitize chronically hypoxic tumor cells to radiotherapy, suggesting a broader therapeutic window for transient DNAPK inhibition combined with radiotherapy.

A transformable gold nanocluster aggregate-based synergistic strategy for potentiated radiation/gene cancer therapy

Nano-radiosensitizers provide a powerful tool for cancer radiation therapy. However, their limited tumor retention/penetration and the inherent or adaptive radiation resistance of tumor cells hamper the clinical success of radiation therapy. Herein, we report a synergistic strategy for potentiated cancer radiation/gene therapy based on transformable gold nanocluster aggregates loaded with antisense oligonucleotide-targeting survivin mRNA (named AuNC-ASON). AuNC-ASON exhibited acidic pH-triggered structure splitting from a gold nanocluster aggregate (around 80 nm) to gold nanocluster (<2 nm), leading to the tumor microenvironment-responsive size transformation of the nano-radiosensitizer and activated release of the loaded antisense oligonucleotides to perform gene silencing. The in vitro experiments demonstrated that AuNC-ASON could amplify and improve the radio-sensitivity of tumor cells (the sensitization enhancement ratio was about 1.81) as a result of the synergistic effect of the transformable gold nanocluster radiosensitizer and survivin gene interference. Remarkably, the size transformation capability realized the high tumor retention/penetration and renal metabolism of AuNC-ASON in vivo and boosted the radio-susceptibility of cancer cells with the assistance of survivin gene interference, synergistically achieving potentiated tumor radiation/gene therapy. The proposed concept of transformable nano-radiosensitizer aggregate-based synergistic therapy can be utilized as a general strategy to guide the design of activatable multifunctional nanosystems for cancer theranostics.

Non-canonical function of DGCR8 in DNA double-strand break repair signaling and tumor radioresistance

In response to DNA double-strand breaks (DSBs), repair proteins are recruited to the damaged sites. Ubiquitin signaling plays a critical role in coordinating protein recruitment during the DNA damage response. Here, we find that the microRNA biogenesis factor DGCR8 promotes tumor resistance to X-ray radiation independently of its Drosha-binding ability. Upon radiation, the kinase ATM and the deubiquitinase USP51 mediate the activation and stabilization of DGCR8 through phosphorylation and deubiquitination. Specifically, radiation-induced ATM-dependent phosphorylation of DGCR8 at serine 677 facilitates USP51 to bind, deubiquitinate, and stabilize DGCR8, which leads to the recruitment of DGCR8 and DGCR8’s binding partner RNF168 to MDC1 and RNF8 at DSBs. This, in turn, promotes ubiquitination of histone H2A, repair of DSBs, and radioresistance. Altogether, these findings reveal the non-canonical function of DGCR8 in DSB repair and suggest that radiation treatment may result in therapy-induced tumor radioresistance through ATM- and USP51-mediated activation and upregulation of DGCR8.

The molecular mechanisms underlying cancer cell radioresistance need to be elucidated. In this study, the authors show that the microRNA biogenesis factor DGCR8 is stabilized by USP51 and ATM upon irradiation and by consequence it promotes the repair of DNA double-strand breaks and radioresistance by recruiting RNF168 to sites of damage.

Cancer-specific loss of TERT activation sensitizes glioblastoma to DNA damage

Glioblastoma is a highly lethal form of brain cancer with no current treatment options that substantially improve patient outcomes. A key therapeutic challenge is the identification of methods that reduce tumor burden while leaving normal cells unaffected. We show that TERT-promoter mutations, common in glioblastoma, lead to TERT reactivation through increased binding of GABPB1L-isoform–containing transcription factor complexes. In turn, we find that cancer-cell–specific inhibition of TERT through GABPB1L reduction results in near-term anti-growth effects and an impaired DNA damage response that profoundly increase the sensitivity of glioblastoma tumors to frontline chemotherapy. Our results thus provide rationale for GABPB1L inhibition combined with temozolomide chemotherapy treatment as a promising therapeutic strategy for glioblastoma.

Most glioblastomas (GBMs) achieve cellular immortality by acquiring a mutation in the telomerase reverse transcriptase (TERT) promoter. TERT promoter mutations create a binding site for a GA binding protein (GABP) transcription factor complex, whose assembly at the promoter is associated with TERT reactivation and telomere maintenance. Here, we demonstrate increased binding of a specific GABPB1L-isoform–containing complex to the mutant TERT promoter. Furthermore, we find that TERT promoter mutant GBM cells, unlike wild-type cells, exhibit a critical near-term dependence on GABPB1L for proliferation, notably also posttumor establishment in vivo. Up-regulation of the protein paralogue GABPB2, which is normally expressed at very low levels, can rescue this dependence. More importantly, when combined with frontline temozolomide (TMZ) chemotherapy, inducible GABPB1L knockdown and the associated TERT reduction led to an impaired DNA damage response that resulted in profoundly reduced growth of intracranial GBM tumors. Together, these findings provide insights into the mechanism of cancer-specific TERT regulation, uncover rapid effects of GABPB1L-mediated TERT suppression in GBM maintenance, and establish GABPB1L inhibition in combination with chemotherapy as a therapeutic strategy for TERT promoter mutant GBM.

Rab12 Promotes Radioresistance of HPV-Positive Cervical Cancer Cells by Increasing G2/M Arrest

Background

HPV-positive (HPV+) cervical cancer cells are more radioresistant compared with HPV-negative (HPV-) cervical cancer cells, but the underlying mechanism is not fully illuminated. Our previous mass spectrometry data showed that Ras-associated binding protein Rab12 was up-regulated by HPV, and this study is to investigate the role of Rab12 in the radioresistance of HPV-positive cervical cancer cells.

Methods

CCK-8 assay, colony formation assay, flow cytometry, and Western blot were performed to determine cell proliferation, apoptosis, cell cycle distribution, and protein expressions. DNA damage and repair levels were measured by comet assays and detection of γ-H2AX, XRCC4, and pBRCA1 protein expressions.

Results

Rab12 mRNA and protein expressions were up-regulated in cervical cancer tissues and HPV+ cervical cancer cells. Knockdown of Rab12 enhanced radiosensitivity while overexpression of Rab12 promotes radioresistance. Knockdown of Rab12 alleviated G2/M arrest by decreasing p-Cdc2(Tyr15) after radiation, which was a result of the reduction of p-Cdc25C(Ser216). Rab12 knockdown caused more DNA double-strand breaks (DSBs) and inhibited DNA homologous recombination repair (HRR) after radiation. Instead, overexpression of Rab12 enhanced radioresistance by increasing G2/M arrest, which provided more time for DNA HRR.

Conclusions

Rab12 may serve as a potential therapeutic target to improve clinical treatment outcome of cervical cancer.

Triclosan induces apoptosis in Burkitt lymphoma-derived BJAB cells through caspase and JNK/MAPK pathways

Burkitt's lymphoma (BL) is the fastest growing human tumor. Current treatment consists of a multiagent regimen of cytotoxic drugs with serious side effjects including tumor lysis, cardiotoxicity, hepatic impairment, neuropathy, myelosuppression, increased susceptibility to malignancy, and death. Furthermore, therapeutic interventions in areas of BL prevalence are not as feasible as in high-income countries. Therefore, there exists an urgent need to identify new therapies with a safer profile and improved accessibility. Triclosan (TCS), an antimicrobial used in personal care products and surgical scrubs, has gained considerable interest as an antitumor agent due to its interference with fatty acid synthesis. Here, we investigate the antitumor properties and associated molecular mechanisms of TCS in BL-derived BJAB cells. Dose-dependent cell death was observed following treatment with 10-100 µM TCS for 24 h, which was associated with membrane phospholipid scrambling, compromised permeability, and cell shrinkage. TCS-induced cell death was accompanied by elevated intracellular calcium, perturbed redox balance, chromatin condensation, and DNA fragmentation. TCS upregulated Bad expression and downregulated that of Bcl2. Moreover, caspase and JNK MAPK signaling were required for the full apoptotic activity of TCS. In conclusion, this report identifies TCS as an antitumor agent and provides new insights into the molecular mechanisms governing TCS-induced apoptosis in BL cells.

[Effectiveness of the DNA double-strand breaks repair system in lymphocytes of patients with cognitive impairments and healthy volunteers]

The individual differences in the efficiency of DNA DSB repair were estimated by the level of residual γH2AX foci after γ-irradiation at a dose of 2 Gy, in lymphocytes of patients with amnestic mild cognitive impairment (AMCI) and Alzheimer's disease (AD) and of healthy volunteers. Lymphocytes were isolated from the peripheral blood of the examined patients and were frozen in a medium for freezing cells. Before the study, the lymphocytes were thawed, suspended in RPMI 1640 culture medium supplemented with 10% inactivated fetal bovine serum, and half of the cells were γ-irradiated at 4°C from a 60Co source on a GUT-200M facility at a dose of 2 Gy (a dose rate of 0.75 Gy/min). Control and irradiated lymphocytes were cultured for 24 h, collected, fixed, and stored until the study of the number of spontaneous and residual foci of γH2AX using fluorescent microscopy after staining with fluorescent labeled antibodies. In lymphocytes of patients with AMCI and AD a higher number of residual γH2AX foci in lymphocytes and the higher number of lymphocytes with foci were found compared with healthy volunteers. This indicates a decrease in the ability to repair DNA DSB in these patients. Indicators of cellular immunity and the concentration of TNF-α in the blood serum in the group of examined patients were normal. In the group of patients with the cognitive impairments (AMCI+AD), a correlation was found between the number of residual foci of γH2AX and the number of CD3+CD4+ lymphocytes and the concentration of proinflammatory cytokine TNF-α in the blood serum. This suggests the development of stronger neuroinflammation in patients with reduced ability to repair DNA DSB in this pathology.

Establishment of a Transformation Coupled in vitro End Joining Assay to Estimate Radiosensitivity in Tumor Cells

Here, we present a modified in vitro end-joining (EJ) assay to quantify EJ capacity, accuracy as well as pathway switch to alternative end-joining (Alt-EJ) or single strand annealing (SSA). A novel transformation assay was established to specifically measure circular repair products, which correlate with classical EJ efficiency. The EJ assay was validated using EJ-deficient mammalian cell lines (Ku80, DNA-PKcs, LigIV, or XRCC4 mutants). A pathway switch to Alt-EJ and SSA was seen exclusively in Ku-deficient cells. Circular EJ product formation correlated with cell survival and DSB repair capacity after X-irradiation. Investigation of 14 HNSCC cell lines revealed differences in the total EJ capacity but a broader variation in the amount of circular repair products. Sequencing of repair junctions in HNSCC cells demonstrated a predominance of high-fidelity EJ and an avoidance of both Alt-EJ and SSA. A significant correlation was observed between the amount of circular repair products, repair of IR-induced DSB and radiosensitivity. Collectively, these data indicate that the presented in vitro-EJ-assay can not only estimate the repair capacity of cancer cells to enable the stratification into radiosensitive or radioresistant, but can also identify repair pathway deregulation such as a switch to Alt-EJ or SSA, which enables tumor targeting.

Exosomal microRNA-26b-5p down-regulates ATF2 to enhance radiosensitivity of lung adenocarcinoma cells

Lung adenocarcinoma (LUAD), as the most common subtype of non‐small cell lung cancer, is responsible for more than 500 000 deaths worldwide annually. In this study, we identify a novel microRNA‐26b‐5p (miR‐26b‐5p) and elucidated its function on LUAD. The survival rate of parent LUAD cells and radiation‐resistant LUAD cells were determined using clonogenic survival assay. We overexpressed or inhibited miR‐26b‐5p in LUAD, and the correlation between activating transcription factor 2 (ATF2) and miR‐26b‐5p was determined using integrated bioinformatics analysis and dual‐luciferase reporter gene assay. Exosomes derived from A549 cell lines were then detected using Western blot assay, followed by co‐transfection with radiation‐resistant A549R cells. LUAD tissues and serum were collected, followed by miR‐26b‐5p relative expression quantification using RT‐qPCR. miR‐26b‐5p was identified as the most differentially expressed miRNA and was down‐regulated in LUAD. Radiation‐resistant cells were more resistant to X‐radiation compared with parent cells. miR‐26b‐5p overexpression and X‐irradiation led to enhanced radiosensitivity of LUAD cells. ATF2 was negatively targeted by miR‐26b‐5p. Exosomal miR‐26b‐5p derived from A549 cells could be transported to irradiation‐resistant LUAD cells and inhibit ATF2 expression to promote DNA damage, apoptosis and radiosensitivity of LUAD cells, which was verified using serum‐based miR‐26b‐5p. Our results show a regulatory network of miR‐26b‐5p on radiosensitivity of LUAD cells, which may serve as a non‐invasive biomarker for LUAD.

Delayed γH2AX foci disappearance in mammary epithelial cells from aged women reveals an age-associated DNA repair defect

Aging is a degenerative process in which genome instability plays a crucial role. To gain insight into the link between organismal aging and DNA repair capacity, we analyzed DNA double-strand break (DSB) resolution efficiency in human mammary epithelial cells from 12 healthy donors of young and old ages. The frequency of DSBs was measured by quantifying the number of γH2AX foci before and after 1Gy of γ-rays and it was higher in cells from aged donors (ADs) at all times analyzed. At 24 hours after irradiation, ADs retained a significantly higher frequency of residual DSBs than young donors (YDs), which had already reached values close to basal levels. The kinetics of DSB induction and disappearance showed that cells from ADs and YDs repair DSBs with similar speed, although analysis of early times after irradiation indicate that a repair defect may lie within the firing of the DNA repair machinery in AD cells. Indeed, using a mathematical model we calculated a constant factor of delay affecting aged human epithelial cells repair kinetics. This defect manifests with the accumulation of DSBs that might eventually undergo illegitimate repair, thus posing a relevant threat to the maintenance of genome integrity in older individuals.

The human papillomavirus confers radiosensitivity in oropharyngeal cancer cells by enhancing DNA double strand break

Background: Patients with Human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPSCC) has better outcomes than those with HPV-negative OPSCC. This may be related to its enhanced radiosensitivity. This study examined the effect of HPV and its E6 oncoprotein on the morphology, radiosensitivity, and repair of radiation-induced DNA damage. Materials and Methods: HPV-negative UM-SCC4 with and without transfection of HPV E6 oncoprotein, HPV-negative UPCI-SCC-089 and HPV-positive UPCI-SCC-099 cell lines were used in this study. The radiosensitivity and morphological changes after radiation were determined by clonogenic assay. Radiation-induced double-strand breaks in the DNA was measured by γ-H2AX foci immunofluorescent assay. Results: The survival fraction after 10 Gy was significantly lower for the HPV-positive SCC-099 cells than for the HPV-negative cells (p = 0.03). The levels of γ-H2AX foci formation and retention were time and cell line-dependent. The γ-H2AX level started to increase at 1 hour and peaked at 4 hours after 10 Gy radiation in the HPV-negative SCC-089 and UM-SCC4 cells before reducing to negligible level (p = 0.0001). In contrast, the HPV-positive UPCI-SCC-099 cells displayed persistent γ-H2AX activity; the expression of γ-H2AX remained high at 48 hours post radiation (p = 0.001). Transfection with the E6 oncoprotein prolonged γ-H2AX formation up to 24 hours in HPV-negative SCC4 cells. HPV-positive SCC-099 cells were more likely to show the classical apoptotic changes of increased cell thickness and increased motility after radiation. Conclusions: This in vitro study confirmed that HPV-positive OPSCC was more radiosensitive. Transfection with the E6 oncoprotein enhanced the radiosensitivity in HPV-negative OPSCC by impairing the DNA repair mechanism and enhancing apoptotic cell death.

Enhanced Expression of IGFBP-3 Reduces Radiosensitivity and Is Associated with Poor Prognosis in Oral Squamous Cell Carcinoma

Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) modulates various cell functions through IGF-dependent or independent mechanisms. However, its biological roles in the radiosensitivity of oral squamous cell carcinoma (OSCC) remain largely unknown. The purpose of this study was to determine the clinical significance and molecular mechanisms of the association between IGFBP-3 and OSCC radiosensitivity. We performed an immunohistochemical analysis of IGFBP-3 in 52 OSCC specimens from patients treated with preoperative chemoradiotherapy and surgery (phase II study). Associations between IGFBP-3 expression and clinicopathological features were also evaluated. In addition, we examined the effects of IGFBP-3 on post-X-ray irradiation radiosensitivity and DNA damage in vitro. High IGFBP-3 expression was significantly correlated with poor chemoradiotherapy responses and prognosis. With IGFBP-3 knockdown, irradiated OSCC cells exhibited significantly higher radiosensitivity compared with that of control cells. Moreover, IGFBP-3 depletion in OSCC cells reduced phosphorylation of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), which is required for DNA double-strand break repair during non-homologous end joining. These findings indicate that IGFBP-3 may have a significant role in regulating DNA repair and is be a potential biomarker for predicting clinical response to radiotherapy and prognosis in OSCC.

Targeting MEK5 impairs nonhomologous end-joining repair and sensitizes prostate cancer to DNA damaging agents

Radiotherapy is commonly used to treat a variety of solid human tumors, including localized prostate cancer. However, treatment failure often ensues due to tumor intrinsic or acquired radioresistance. Here we find that the MEK5/ERK5 signaling pathway is associated with resistance to genotoxic stress in aggressive prostate cancer cells. MEK5 knockdown by RNA interference sensitizes prostate cancer cells to ionizing radiation (IR) and etoposide treatment, as assessed by clonogenic survival and short-term proliferation assays. Mechanistically, MEK5 downregulation impairs phosphorylation of the catalytic subunit of DNA-PK at serine 2056 in response to IR or etoposide treatment. Although MEK5 knockdown does not influence the initial appearance of radiation- and etoposide-induced γH2AX and 53BP1 foci, it markedly delays their resolution, indicating a DNA repair defect. A cell-based assay shows that non-homologous end joining (NHEJ) is compromised in cells with ablated MEK5 protein expression. Finally, MEK5 silencing combined with focal irradiation causes strong inhibition of tumor growth in mouse xenografts, compared with MEK5 depletion or radiation alone. These findings reveal a convergence between MEK5 signaling and DNA repair by NHEJ in conferring resistance to genotoxic stress in advanced prostate cancer and suggest targeting MEK5 as an effective therapeutic intervention in the management of this disease.

Comparable radiation response of ex vivo and in vivo irradiated tumor samples determined by residual γH2AX

PURPOSE

a) To investigate if an ex vivo cultured and irradiated tumor biopsy reflects and predicts the radiation response of the corresponding in vivo irradiated tumor measured with the DNA double strand break marker γH2AX foci.

MATERIALS AND METHODS

Five human head and neck squamous cell carcinoma (hHNSCC) xenograft models were used. Fine needle biopsies were taken from anesthetized tumor-bearing NMRI nude mice prior to in vivo single dose irradiation (0, 2, 4, or 8 Gy) under ambient blood flow. Biopsies were ex vivo reoxygenated and irradiated with equivalent doses. Tumors and biopsies were fixed 24 h post irradiation, and γH2AX foci were assessed in oxygenated tumor regions.

RESULTS

Linear regression analysis showed comparable slopes of the residual γH2AX foci dose-response curves in four out of five hHNSCC models when in vivo and ex vivo cohorts were compared. The slopes from ex vivo biopsies and in vivo tumors could classify the respective tumor model as sensitive or resistant according to the intrinsic radiation sensitivity (TCD₅₀).

CONCLUSION

The ability of ex vivo irradiated tumor biopsies to reflect and predict the intrinsic radiation response of in vivo tumors increases the translational potential of the ex vivo γH2AX foci assay as a diagnostic tool for clinical practice.

Why Does the Type of Halogen Atom Matter for the Radiosensitizing Properties of 5-Halogen Substituted 4-Thio-2'-Deoxyuridines?

Radiosensitizing properties of substituted uridines are of great importance for radiotherapy. Very recently, we confirmed 5-iodo-4-thio-2'-deoxyuridine (ISdU) as an efficient agent, increasing the extent of tumor cell killing with ionizing radiation. To our surprise, a similar derivative of 4-thio-2'-deoxyuridine, 5-bromo-4-thio-2'-deoxyuridine (BrSdU), does not show radiosensitizing properties at all. In order to explain this remarkable difference, we carried out a radiolytic (stationary and pulse) and quantum chemical studies, which allowed the pathways to all radioproducts to be rationalized. In contrast to ISdU solutions, where radiolysis leads to 4-thio-2'-deoxyuridine and its dimer, no dissociative electron attachment (DEA) products were observed for BrSdU. This observation seems to explain the lack of radiosensitizing properties of BrSdU since the efficient formation of the uridine-5-yl radical, induced by electron attachment to the modified nucleoside, is suggested to be an indispensable attribute of radiosensitizing uridines. A larger activation barrier for DEA in BrSdU, as compared to ISdU, is probably responsible for the closure of DEA channel in the former system. Indeed, besides DEA, the XSdU anions may undergo competitive protonation, which makes the release of X- kinetically forbidden.

OTU deubiquitinase 4 is silenced and radiosensitizes non-small cell lung cancer cells via inhibiting DNA repair

Background

Radiotherapy is becoming one major therapeutics for non-small cell lung cancer (NSCLC). Identifying novel radiosensitizers will greatly increase the efficacy of radiotherapy and benefit more patients. OTU deubiquitinase 4 (OTUD4) has been reported involved in DNA damage repair pathways and could be a potential target for chemotherapy therapy. This study aimed to investigate the roles of OTUD4 in regulation of radiosensitivity of NSCLC via modulating DNA repair.

Methods

The expression of OTUD4, γ-H2Ax and ATM/CHK2/p53 pathway-related signaling molecules were detected by Western blotting and QRT-PCR. The methylation of OTUD4 promoter was investigated by 5-aza-deoxycytidine treatment, methylation-specific PCR and bisulfite genomic sequencing assays. Radiosensitivity was assessed by the clonogenic formation assay. Cell cycle, cell apoptosis were analyzed by flow cytometry. DNA damage and repair were determined by comet assay, γ-H2Ax foci staining and flow cytometry.

Results

OTUD4 is dramatically downregulated in NSCLC and its downregulation significantly correlates with poor prognosis of NSCLC patients. Promoter hypermethylation is responsible for the loss of OTUD4 expression in NSCLC cells. Overexpression of OTUD4 increases radiosensitivity of NSCLC cells exhibiting as impaired clonogenic formation ability, enhanced cell cycle arrest and increased cell apoptosis. Moreover, molecular mechanism study reveals that OTUD4 radiosensitizs NSCLC cells via ATM/CHK2/P53 signaling and inhibiting homology-directed repair of DNA double strand breaks induced by ionizing radiation.

Conclusions

This study uncovers a tumor-suppressing role of OTUD4 and that OTUD4 is a potential radiosensitizer for NSCLC.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0816-z) contains supplementary material, which is available to authorized users.

Expression of γ-H2AX and patient prognosis in breast cancer cohort

H2AX phosphorylation is a novel marker of DNA double-stranded breaks. In the present study, we assessed the γ-H2AX expression, its association with other clinicopathologic characteristics, and the prognosis in a cohort of 97 patients with breast cancer. Ninety-seven specimens of tumor tissue and 77 adjacent normal tissues from patients with breast cancer were examined. All patients underwent modified radical mastectomy or local tumor resection without lymph node dissection. γ-H2AX expression was assessed by standard immunohistochemistry. Patients were followed after surgery for a mean duration of 70.1 ± 18.7 months (range, 6-93 months). The γ-H2AX staining was positive in 27 (27.8%) patients. The positive rates of H2AX were 26.0% and 2.6% in tumor tissue and adjacent normal tissues, respectively. γ-H2AX positive status was negatively associated with TNM staging, with 24 positive cases (32.4%) in TNM staging I-II, while no positive cases in TNM staging III-IV (P = 0.026). Sixteen patients (16.5%) died during the follow-up. No significant association between γ-H2AX expression and patient survival was detected. The unadjusted HR (hazard ratio) for γ-H2AX positive was 0.84 (95% CI: 0.27, 2.60). In TNM staging subgroup analysis, death only occurred in γ-H2AX negative patients. Our study is the first study to demonstrate that expression of γ-H2AX is associated with TNM staging. Due to the small sample and limited follow-up time, we did not observe a significant association between γ-H2AX and patient survival. γ-H2AX expression could be a potential biomarker for cancer diagnosis and prediction, and further studies are in need.

Radiosensitivity of Cancer Cells Is Regulated by Translationally Controlled Tumor Protein

Translationally controlled tumor protein (TCTP) is a ubiquitous multifunctional protein that is essential for cell survival. This study reveals that the regulation of radiosensitivity of cancer cells is yet another function of TCTP. The relationship between endogenous TCTP levels and sensitivity to radiation was examined in breast cancer cell lines (T47D, MDA-MB-231, and MCF7) and lung cancer cells lines (A549, H1299, and H460). Cancer cells with high expression levels of TCTP were more resistant to radiation. TCTP overexpression inhibited radiation-induced cell death, while silencing TCTP led to an increase in radiosensitivity. DNA damage in the irradiated TCTP-silenced A549 cells was greater than in irradiated control shRNA-transfected A549 cells. p53, a well-known reciprocal regulator of TCTP, was increased in irradiated TCTP down-regulated A549 cells. Moreover, introduction of p53 siRNA in TCTP knocked-down A549 cells abrogated the increased radiosensitivity induced by TCTP knockdown. An in vivo xenograft study also confirmed enhanced radiosensitivity in TCTP down-regulated A549 cells. These findings suggest that TCTP has the potential to serve as a therapeutic target to overcome radiation resistance in cancer, a major problem for the effective treatment of cancers.

5-Iodo-4-thio-2'-Deoxyuridine as a Sensitizer of X-ray Induced Cancer Cell Killing

Nucleosides, especially pyrimidines modified in the C5-position, can act as radiosensitizers via a mechanism that involves their enzymatic triphosphorylation, incorporation into DNA, and a subsequent dissociative electron attachment (DEA) process. In this paper, we report 5-iodo-4-thio-2'-deoxyuridine (ISdU) as a compound that can effectively lead to ionizing radiation (IR)-induced cellular death, which is proven by a clonogenic assay. The test revealed that the survival of cells, pre-treated with 10 or 100 µM solution of ISdU and exposed to 0.5 Gy of IR, was reduced from 78.4% (for non-treated culture) to 67.7% and to 59.8%, respectively. For a somewhat higher dose of 1 Gy, the surviving fraction was reduced from 68.2% to 54.9% and to 40.8% for incubation with 10 or 100 µM ISdU, respectively. The cytometric analysis of histone H2A.X phosphorylation showed that the radiosensitizing effect of ISdU was associated, at least in part, with the formation of double-strand breaks. Moreover, the cytotoxic test against the MCF-7 breast cancer cell line and human dermal fibroblasts (HDFa line) confirmed low cytotoxic activity of ISdU. Based on the results of steady state radiolysis of ISdU with a dose of 140 Gy and quantum chemical calculations explaining the origin of the MS detected radioproducts, the molecular mechanism of sensitization by ISdU was proposed. In conclusion, we found ISdU to be a potential radiosensitizer that could improve anticancer radiotherapy.

Exosome-derived miR-339-5p mediates radiosensitivity by targeting Cdc25A in locally advanced esophageal squamous cell carcinoma

Cancer cells associated with radioresistance are likely to give rise to local recurrence and distant metastatic relapse. However, it remains unclear whether specific miRNAs have direct roles in radioresistance and/or prognosis. In this study, we find that miR-339-5p promotes radiosensitivity, and is downregulated in radioresistant subpopulations of esophageal cancer cells. Notably, miR-339-5p was selectively secreted into blood via exosomes, and that higher serum miR-339-5p levels were positively associated with radiotherapy sensitivity and good survival. Moreover, miR-339-5p expression was downregulated in the T3/T4 stage compared with T1/T2 stage in esophageal squamous cell carcinoma (ESCC) patients (P = 0.04), and low miR-339-5p expression in tissue was significantly associated with poor overall survival (P = 0.036) and disease-free survival (P = 0.037). Overexpression of miR-339-5p enhanced radiosensitivity in vitro and in vivo. Mechanistically, miR-339-5p enhances radiosensitivity by targeting Cdc25A, and is transcriptionally regulated by Runx3. Correlations were observed between miR-339-5p levels and Cdc25A/Runx3 levels in tissue samples. Intriguingly, combined analysis of miR-339-5p expression with Runx3 increased the separation of the survival curves obtained for either gene alone in the TCGA datasets (P = 0.009). Overall, exosome-derived miR-339-5p mediates radiosensitivity through downregulation of Cdc25A, and predicts pathological response to preoperative radiotherapy in locally advanced ESCC, suggesting it could be a promising non-invasive biomarker for facilitating personalized treatments.

Diagnostic and Prognostic Biomarkers of Adrenal Cortical Carcinoma

The diagnosis of low-grade adrenal cortical carcinoma (ACC) confined to the adrenal gland can be challenging. Although there are diagnostic and prognostic molecular tests for ACC, they remain largely unutilized. We examined the diagnostic and prognostic value of altered reticulin framework and the immunoprofile of biomarkers including IGF-2, proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage repair (PBK, γ-H2AX), telomere regulation (DAX, ATRX), wnt-signaling pathway (beta-catenin) and PI3K signaling pathway (PTEN, phospho-mTOR) in a tissue microarray of 50 adenomas and 43 carcinomas that were characterized for angioinvasion as defined by strict criteria, Weiss score, and mitotic rate-based tumor grade. IGF-2 and proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage proteins (PBK, γ-H2AX), regulators of telomeres (DAXX, ATRX), and beta-catenin revealed characteristic expression profiles enabling the distinction of carcinomas from adenomas. Not all biomarkers were informative in all carcinomas. IGF-2 was the most useful biomarker of malignancy irrespective of tumor grade and cytomorphologic features, as juxtanuclear Golgi-pattern IGF-2 reactivity optimized for high specificity was identified in up to 80% of carcinomas and in no adenomas. Loss rather than qualitative alterations of the reticulin framework yielded statistical difference between carcinoma and adenoma. Angioinvasion defined as tumor cells invading through a vessel wall and intravascular tumor cells admixed with thrombus proved to be the best prognostic parameter, predicting adverse outcome in the entire cohort as well as within low-grade ACCs. Low mitotic tumor grade, Weiss score, global loss of DAXX expression, and high phospho-mTOR expression correlated with disease-free survival, but Weiss score and biomarkers failed to predict adverse outcome in low-grade disease. Our results underscore the importance of careful morphologic assessment coupled with ancillary diagnostic and prognostic biomarkers of ACC.

Evaluating Gamma-H2AX Expression as a Biomarker of DNA Damage after X-ray in Angiography Patients

OBJECTIVE

Coronary heart disease (CHD) is one of the most common diseases. Coronary angiography (CAG) is an important apparatus used to diagnose and treat this disease. Since angiography is performed through exposure to ionizing radiation, it can cause harmful effects induced by double-stranded breaks in DNA which is potentially life-threatening damage. The aim of the present study is to investigate phosphorylation of Histone H2AX in the location of double-stranded breaks in peripheral blood lymphocytes as an indication of biological effects of radiation on angiography.

MATERIALS AND METHODS

This method is based on the phosphorylation measurement of Histone (gamma-H2AX or γ-H2AX) levels on serine 139 after the formation of DNA double-strand break. 5 cc of blood samples from 24 patients undergoing angiography were taken pre- and post-radiation. Blood lymphocytes were extracted, fixed and stained with specific γ-H2AX antibodies. Finally, the percentage of phosphorylation of Histone H2AX as an indicator of double-strand break was measured by a cytometry technique.

RESULTS

An increase was observed in all patients' percentage of phosphorylated Histone H2AX (double-stranded breaks DNA) after radiation (20.15 ± 14.18) compared to pre-exposure time (1.52 ± 0.34). Also, the mean of DNA double-strand break is shown in a linear correlation with DAP.

DISCUSSION

Although induction of DNA double-strand breaks was associated with the radiation dose in patients, the effect of individual factors such as radio-sensitivity and regenerative capacity should not be ignored. In the future, if we are able to measure DNA damage response in every angiography patient, we will use it as a biomarker for the patient dose; this will promote public health.

CONCLUSION

Using flow cytometers readings done automatically is possible to detect γ-H2AX in the number of blood cells, therefore, the use of this technique could play a significant role in monitoring patients.

Dotting the eyes: mouse strain dependency of the lens epithelium to low dose radiation-induced DNA damage

PURPOSE

Epidemiological evidence regarding the radiosensitivity of the lens of the eye and radiation cataract development has led to changes in the EU Basic Safety Standards for protection of the lens against ionizing radiation. However, mechanistic details of lens radiation response pathways and their significance for cataractogenesis remain unclear. Radiation-induced DNA damage and the potential impairment of repair pathways within the lens epithelium, a cell monolayer that covers the anterior hemisphere of the lens, are likely to be involved.

MATERIALS AND METHODS

In this work, the lens epithelium has been analyzed for its DNA double-strand break (DSB) repair response to ionizing radiation. The responses of epithelial cells located at the anterior pole (central region) have been compared to at the very periphery of the monolayer (germinative and transitional zones). Described here are the different responses in the two regions and across four strains (C57BL/6, 129S2, BALB/c and CBA/Ca) over a low dose (0-25 mGy) in-vivo whole body X-irradiation range up to 24 hours post exposure.

RESULTS

DNA damage and repair as visualized through 53BP1 staining was present across the lens epithelium, although repair kinetics appeared non-uniform. Epithelial cells in the central region have significantly more 53BP1 foci. The sensitivities of different mouse strains have also been compared.

CONCLUSIONS

129S2 and BALB/c showed higher levels of DNA damage, with BALB/c showing significantly less inter-individual variability and appearing to be a more robust model for future DNA damage and repair studies. As a result of this study, BALB/c was identified as a suitable radiosensitive lens strain to detect and quantify early low dose ionizing radiation DNA damage effects in the mouse eye lens specifically, as an indicator of cataract formation.

Identification of brain metastasis genes and therapeutic evaluation of histone deacetylase inhibitors in a clinically relevant model of breast cancer brain metastasis

Breast cancer brain metastases remain largely incurable. Although several mouse models have been developed to investigate the genes and mechanisms regulating breast cancer brain metastasis, these models often lack clinical relevance since they require the use of immunocompromised mice and/or are poorly metastatic to brain from the mammary gland. We describe the development and characterisation of an aggressive brain metastatic variant of the 4T1 syngeneic model (4T1Br4) that spontaneously metastasises to multiple organs, but is selectively more metastatic to the brain from the mammary gland than parental 4T1 tumours. As seen by immunohistochemistry, 4T1Br4 tumours and brain metastases display a triple-negative phenotype, consistent with the high propensity of this breast cancer subtype to spread to brain. In vitro assays indicate that 4T1Br4 cells have an enhanced ability to adhere to or migrate across a brain-derived endothelial monolayer and greater invasive response to brain-derived soluble factors compared to 4T1 cells. These properties are likely to contribute to the brain selectivity of 4T1Br4 tumours. Expression profiling and gene set enrichment analyses demonstrate the clinical relevance of the 4T1Br4 model at the transcriptomic level. Pathway analyses implicate tumour-intrinsic immune regulation and vascular interactions in successful brain colonisation, revealing potential therapeutic targets. Evaluation of two histone deacetylase inhibitors, SB939 and 1179.4b, shows partial efficacy against 4T1Br4 metastasis to brain and other sites in vivo, and potent radio-sensitising properties in vitro. The 4T1Br4 model provides a clinically relevant tool for mechanistic studies and to evaluate novel therapies against brain metastasis.

This article has an associated First Person interview with Soo-Hyun Kim, joint first author of the paper.

Summary: The authors introduce a new syngeneic mouse model of spontaneous breast cancer brain metastasis, demonstrate its phenotypic, functional and transcriptomic relevance to human TNBC brain metastasis, and test novel therapies.

Nonstructural Protein 5A Impairs DNA Damage Repair: Implications for Hepatitis C Virus-Mediated Hepatocarcinogenesis

RAD51-associated protein 1 (RAD51AP1) is a member of the multiprotein complexes postulated to carry out RAD51-mediated homologous recombination and DNA repair in mammalian cells. In the present study, we showed that hepatitis C virus (HCV) NS5A directly bound RAD51AP1 and increased the protein level of RAD51AP1 through modulation of the ubiquitin-proteasome pathway. We also demonstrated that RAD51AP1 protein levels were increased in the liver tissues of HCV-infected patients and NS5A-transgenic mice. Importantly, NS5A impaired DNA repair by disrupting the RAD51/RAD51AP1/UAF1 complex and rendered HCV-infected cells more sensitive to DNA damage. Silencing of RAD51AP1 expression resulted in a decrease of viral propagation. We further demonstrated that RAD51AP1 was involved in the assembly step of the HCV life cycle by protecting viral RNA. These data suggest that HCV exploits RAD51AP1 to promote viral propagation and thus that host DNA repair is compromised in HCV-infected cells. Overall, our findings provide mechanistic insight into the pathogenesis of HCV infection.IMPORTANCE Chronic infection with HCV is the leading cause of hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying HCV-induced HCC are not fully understood. Here we demonstrate that the HCV NS5A protein physically interacts with RAD51AP1 and increases the RAD51AP1 protein level through modulation of the ubiquitin-proteasome pathway. HCV coopts host RAD51AP1 to protect viral RNA at an assembly step of the HCV life cycle. Note that the RAD51 protein accumulates in the cytoplasm of HCV-infected cells, and thus the RAD51/RAD51AP1/UAF1-mediated DNA damage repair system in the nucleus is compromised in HCV-infected cells. Our data may provide new insight into the molecular mechanisms of HCV-induced pathogenesis.

Radiation-induced unrepairable DSBs: their role in the late effects of radiation and possible applications to biodosimetry

Although the vast majority of DNA damage induced by radiation exposure disappears rapidly, some lesions remain in the cell nucleus in very small quantities for days to months. These lesions may cause a considerable threat to an organism and include certain types of DNA double-strand breaks (DSBs) called 'unrepairable DSBs'. Unrepairable DSBs are thought to cause persistent malfunctioning of cells and tissues or cause late effects of radiation, especially the induction of delayed cell death, mutation, senescence, or carcinogenesis. Moreover, the measurement of unrepairable DSBs could potentially be used for retrospective biodosimetry or for identifying individuals at greater risk for developing the adverse effects associated with radiotherapy or chemotherapy. This review summarizes the concept of unrepairable DSBs in the context of persistent repair foci formed at DSBs.