Gene expression signature predicts radiation sensitivity in cell lines using the integral of dose-response curve

BACKGROUND

Although substantial efforts have been made to build molecular biomarkers to predict radiation sensitivity, the ability to accurately stratify the patients is still limited. In this study, we aim to leverage large-scale radiogenomics datasets to build genomic predictors of radiation response using the integral of the radiation dose-response curve.

METHODS

Two radiogenomics datasets consisting of 511 and 60 cancer cell lines were utilized to develop genomic predictors of radiation sensitivity. The intrinsic radiation sensitivity, defined as the integral of the dose-response curve (AUC) was used as the radioresponse variable. The biological determinants driving AUC and SF2 were compared using pathway analysis. To build the predictive model, the largest and smallest datasets consisting of 511 and 60 cancer cell lines were used as the discovery and validation cohorts, respectively, with AUC as the response variable.

RESULTS

Utilizing a compendium of three pathway databases, we illustrated that integral of the radiobiological model provides a more comprehensive characterization of molecular processes underpinning radioresponse compared to SF2. Furthermore, more pathways were found to be unique to AUC than SF2-30, 288 and 38 in KEGG, REACTOME and WIKIPATHWAYS, respectively. Also, the leading-edge genes driving the biological pathways using AUC were unique and different compared to SF2. With regards to radiation sensitivity gene signature, we obtained a concordance index of 0.65 and 0.61 on the discovery and validation cohorts, respectively.

CONCLUSION

We developed an integrated framework that quantifies the impact of physical radiation dose and the biological effect of radiation therapy in interventional pre-clinical model systems. With the availability of more data in the future, the clinical potential of this signature can be assessed, which will eventually provide a framework to integrate genomics into biologically-driven precision radiation oncology.

Induction immunochemotherapy followed by radiotherapy for patients with unresectable locally advanced or metastatic esophageal cancer: A propensity score-matched analysis

BACKGROUND

The study aimed to investigate the efficacy of induction immunochemotherapy before radiotherapy (RT) for patients with locally advanced or metastatic esophageal cancer.

METHODS

Patients with unresectable locally advanced or metastatic esophageal cancer who received induction immunochemotherapy followed by RT (ICIs + RT group) and RT alone (RT group) were retrospectively identified in two cancer centers, respectively. Propensity score matching (PSM) was used to balance the potential confounders between the two groups. Overall survival (OS), progression-free survival (PFS), and recurrence patterns were evaluated.

RESULTS

A total of 467 patients were reviewed, and 66 were matched in each group. After PSM, the 1- and 2-year OS rates were 84.6% and 57.9% in ICIs + RT group, and 71.1% and 43.0% in RT group (HR 0.60, 95% CI 0.36-1.00, p = 0.050). The absolute increase of restricted mean survival time (RMST) for OS in ICIs + RT group compared with RT group were 0.89 years (p = 0.023) at one year and 2.59 years at two years (p = 0.030). The median PFS time, 1- and 2-year PFS rates were 20.3 months, 69.3%, and 45.7% in ICIs + RT group, and 12.2 months, 51.4%, and 35.8% in RT group (HR 0.64, 95% CI 0.41-0.99, p = 0.045). The cumulative locoregional recurrence (LRR) rate was significantly lower in ICIs + RT group (1-year rate, 17.4% vs. 38.8%, p = 0.011), and distant metastasis (DM) rates were comparable (p = 0.755). Consolidation ICIs was associated with a trend of improved 1-year OS and PFS.

CONCLUSION

Induction immunochemotherapy followed by RT might improve locoregional control and survival outcomes for patients with unresectable locally advanced or metastatic esophageal cancer.

A Clinical Conundrum with Diagnostic and Therapeutic Challenge: a Tale of Two Disorders in One Case

Living organisms are exposed to exogenous and endogenous agents that affect genomic integrity by creating DNA double strand breaks (DSBs). These breaks are repaired by DNA repair proteins to maintain homeostasis. Defects in DNA repair pathways also affect lymphocyte development and maturation, as DSB sites are critical intermediates for rearrangements required for V(D)J recombination. Recent classifications for inborn errors of immunity (IEIs) have listed DNA repair defect genes in a separate group, which suggests the importance of these genes for adaptive and innate immunity. We report an interesting case of a young female (index P1) with mutations in two different genes, DCLRE1C and FANCA, involved in DNA repair pathways. She presented with clinical manifestations attributed to both defects. With the advent of NGS, more than one defect is increasingly identified in patients with IEIs. Familial segregation studies and appropriate functional assays help ascertain the pathogenicity of these mutations and provide appropriate management and genetic counseling.

Radiosensitizing oxygenation changes in murine tumors treated with VEGF-ablation therapy are measurable using oxygen enhanced-MRI (OE-MRI)

PURPOSE

There is a significant need for a widely available, translatable, sensitive and non-invasive imaging biomarker for tumor hypoxia in radiation oncology. Treatment-induced changes in tumor tissue oxygenation can alter the sensitivity of cancer tissues to radiation, but the relative difficulty in monitoring the tumor microenvironment results in scarce clinical and research data. Oxygen-Enhanced MRI (OE-MRI) uses inhaled oxygen as a contrast agent to measure tissue oxygenation. Here we investigate the utility of dOE-MRI, a previously validated imaging approach employing a cycling gas challenge and independent component analysis (ICA), to detect VEGF-ablation treatment-induced changes in tumor oxygenation that result in radiosensitization.

METHODS

Murine squamous cell carcinoma (SCCVII) tumor-bearing mice were treated with 5 mg/kg anti-VEGF murine antibody B20 (B20-4.1.1, Genentech) 2-7 days prior to radiation treatment, tissue collection or MR imaging using a 7 T scanner. dOE-MRI scans were acquired for a total of three repeated cycles of air (2 min) and 100% oxygen (2 min) with responding voxels indicating tissue oxygenation. DCE-MRI scans were acquired using a high molecular weight (MW) contrast agent (Gd-DOTA based hyperbranched polygylcerol; HPG-GdF, 500 kDa) to obtain fractional plasma volume (fPV) and apparent permeability-surface area product (aPS) parameters derived from the MR concentration-time curves. Changes to the tumor microenvironment were evaluated histologically, with cryosections stained and imaged for hypoxia, DNA damage, vasculature and perfusion. Radiosensitizing effects of B20-mediated increases in oxygenation were evaluated by clonogenic survival assays and by staining for DNA damage marker γH2AX.

RESULTS

Tumors from mice treated with B20 exhibit changes to their vasculature that are consistent with a vascular normalization response, and result in a temporary period of reduced hypoxia. DCE-MRI using injectable contrast agent HPG-GDF measured decreased vessel permeability in treated tumors, while dOE-MRI using inhaled oxygen as a contrast agent showed greater tissue oxygenation. These treatment-induced changes to the tumor microenvironment result in significantly increased radiation sensitivity, illustrating the utility of dOE-MRI as a non-invasive biomarker of treatment response and tumor sensitivity during cancer interventions.

CONCLUSIONS

VEGF-ablation therapy-mediated changes to tumor vascular function measurable using DCE-MRI techniques may be monitored using the less invasive approach of dOE-MRI, an effective biomarker of tissue oxygenation that can monitor treatment response and predict radiation sensitivity.

Chromosomal radiosensitivity in oncological and non-oncological patients with rheumatoid arthritis and connective tissue diseases

BACKGROUND

The risk of developing late radiotoxicity after radiotherapy in patients with high chromosomal radiosensitivity after radiotherapy could potentially be higher compared to the risk in patients with average radiosensitivity. In case of extremely high radiosensitivity, dose reduction may be appropriate. Some rheumatic diseases (RhD), including connective tissue diseases (CTDs) appear to be associated with higher radiosensitivity. The question arises as to whether patients with rheumatoid arthritis (RA) also generally have a higher radiosensitivity and whether certain parameters could indicate clues to high radiosensitivity in RA patients which would then need to be further assessed before radiotherapy.

METHODS

Radiosensitivity was determined in 136 oncological patients with RhD, 44 of whom were RA patients, and additionally in 34 non-oncological RA patients by three-colour fluorescence in situ hybridization (FiSH), in which lymphocyte chromosomes isolated from peripheral blood are analysed for their chromosomal aberrations of an unirradiated and an with 2 Gy irradiated blood sample. The chromosomal radiosensitivity was determined by the average number of breaks per metaphase. In addition, correlations between certain RA- or RhD-relevant disease parameters or clinical features such as the disease activity score 28 and radiosensitivity were assessed.

RESULTS

Some oncological patients with RhD, especially those with connective tissue diseases have significantly higher radiosensitivity compared with oncology patients without RhD. In contrast, the mean radiosensitivity of the oncological patients with RA and other RhD and the non-oncological RA did not differ. 14 of the 44 examined oncological RA-patients (31.8%) had a high radiosensitivity which is defined as ≥ 0.5 breaks per metaphase. No correlation of laboratory parameters with radiosensitivity could be established.

CONCLUSIONS

It would be recommended to perform radiosensitivity testing in patients with connective tissue diseases in general. We did not find a higher radiosensitivity in RA patients. In the group of RA patients with an oncological disease, a higher percentage of patients showed higher radiosensitivity, although the average radiosensitivity was not high.

Biological effects of cancer stem cells irradiated by charged particle: a systematic review of in vitro studies

PURPOSE

The existence of cancer stem cells (CSCs) is closely related to tumor recurrence, metastasis, and resistance to chemoradiotherapy. In addition, given the unique physical and biological advantages of charged particle, we hypothesized that charged particle irradiation would produce strong killing effects on CSCs. The purpose of our systematic review is to evaluate the biological effects of CSCs irradiated by charged particle, including proliferation, invasion, migration, and changes in the molecular level.

METHODS

We searched PubMed, EMBASE, and Web of Science until 17 march 2022 according to the key words. Included studies have to be vitro studies of CSCs irradiated by charged particle. Outcomes included one or more of radiation sensitivity, proliferation, metastasis, invasion, and molecular level changes, like DNA damage after been irradiated.

RESULTS

Eighteen studies were included in the final analysis. The 18 articles include 12-carbon ion irradiation, 4-proton irradiation, 1 α-particle irradiation, 1-carbon ion combine proton irradiation.

CONCLUSION

Through the extraction and analysis of data, we came to this conclusion: CSCs have obvious radio-resistance compared with non-CSCs, and charged particle irradiation or in combination with drugs could overcome this resistance, specifically manifested in inhibiting CSCs' proliferation, invasion, migration, and causing more and harder to repair DNA double-stranded breaks (DSB) of CSCs.

The measurement of NRF2 and TP53 in blood expects radiotherapeutic sensitivity in patients with esophageal cancer

OBJECTIVE

This study investigates the relationship between the mRNA expression of nuclear factor erythroid 2-related factor 2 (NRF2) and Tumor protein p53 (TP53) in circulating tumor cells (CTC) and sensitivity to radiotherapy in patients with esophageal cancer. To investigate the relationship between cytokines IL-6, CD8⁺, and NRF2 during patient treatment and their predictive role for treatment.

METHODS

Radiosensitivity was assessed by measuring a morphological or functional change in the tumor in response to ionizing radiation. Fasting venous anticoagulated blood (EDTA anticoagulation) was drawn from patients, and the Trizol-chloroform two-step method was used for RNA extraction. Data were collected from 45 patients admitted with radiotherapy alone from January 2018 to December 2021. The expression levels of NRF2mRNA (Messenger Ribose Nucleic Acid) and TP53mRNA in CTCs were detected by reverse transcription-polymerase chain reaction (RT-PCR). Pre- and post-treatment changes in IL-6 and CD8⁺ were recorded. The correlation between their expression level and the clinical stage, radiotherapy sensitivity, and efficacy of patients was analyzed.

RESULTS

Twenty-six cases were sensitive to radiotherapy, and 19 were resistant, for a radiotherapy sensitivity rate of 58.8%. NRF2mRNA and TP53mRNA values increased in 19 radiotherapy-resistant patients and decreased in 26 radiotherapy-sensitive patients compared with those before radiotherapy (P = 0.001, P＜0.05). The ΔCT values of NRF2mRNA and TP53mRNA before treatment were moderately correlated with prognosis (P < 0.002). Inflammatory cytokine IL-6 was elevated in 22 of 45 patients after radiation, P = 0.04. NRF2 mRNA level was consistently elevated with CD8⁺ in 10 patients, P = 0.02.

CONCLUSIONS

The expression of NRF2mRNA and TP53mRNA in the CTCs found in the peripheral blood of patients with esophageal squamous carcinoma was significantly associated with the sensitivity to radiotherapy. NRF2 mRNA level was consistently elevated with CD8⁺ and IL-6 in patients.

Ionizing radiation induced DNA damage via ROS production in nano ozonized oil treated B-16 melanoma and OV-90 ovarian cells

In this study, we aimed to investigate ozonized oil nanoemulsions (OZNEs) as a radiosensitizer within B-16 melanoma and OV-90 ovarian cells under X-ray irradiation in vitro. Radiation sensitivity of OZNE treated B-16 melanoma cells and OV-90 ovarian cells were evaluated by performing cell cycle analysis, Reactive Oxygen Species (ROS) and ɣ-H2AX assays by flow cytometry. OZNEs induced G0-1 phase arrest of B-16 melanoma cells for all radiation doses and G2/M arrest for 8 Gy and 15 Gy doses. OZNE treated B-16 melanoma and OV-90 ovarian cells induced DNA damage via the increase in ROS production, as well as significant increase in the expression of ɣ-H2AX under even low doses of radiation (2 Gy). Thus, OZNEs are suggested to help to optimize cancer RT as a radiosensitizer and further studies will significantly outperform recent advances in this field.

Changing Radiotherapy Paradigms in Penile Cancer

Radiation therapy (RT) has not been prominent in the treatment of penile cancer because of poorly reproducible results when used in the adjuvant setting. A genomic signature has recently been described that assays radiosensitivity of tumors and informs radiotherapy doses in these cases. Clinical validation in more than 1600 patients demonstrated associations with both overall survival and time to first recurrence. In addition, the signature predicted and quantified the therapeutic benefit of RT for each individual patient. Since penile cancer patients were not part of this analysis, we applied the model to patients with primary and nodal penile cancer tissue and clinical outcomes.

Patient summary: Radiotherapy has not been widely used for treatment of penile cancer. New genetic data suggest that radiation doses commonly used to treat penile cancer are too low. This would explain prior poor results using radiation in this disease.

Opposite effects of the triple target (DNA-PK/PI3K/mTOR) inhibitor PI-103 on the radiation sensitivity of glioblastoma cell lines proficient and deficient in DNA-PKcs

BACKGROUND

Radiotherapy is routinely used to combat glioblastoma (GBM). However, the treatment efficacy is often limited by the radioresistance of GBM cells.

METHODS

Two GBM lines MO59K and MO59J, differing in intrinsic radiosensitivity and mutational status of DNA-PK and ATM, were analyzed regarding their response to DNA-PK/PI3K/mTOR inhibition by PI-103 in combination with radiation. To this end we assessed colony-forming ability, induction and repair of DNA damage by γH2AX and 53BP1, expression of marker proteins, including those belonging to NHEJ and HR repair pathways, degree of apoptosis, autophagy, and cell cycle alterations.

RESULTS

We found that PI-103 radiosensitized MO59K cells but, surprisingly, it induced radiation resistance in MO59J cells. Treatment of MO59K cells with PI-103 lead to protraction of the DNA damage repair as compared to drug-free irradiated cells. In PI-103-treated and irradiated MO59J cells the foci numbers of both proteins was higher than in the drug-free samples, but a large portion of DNA damage was quickly repaired. Another cell line-specific difference includes diminished expression of p53 in MO59J cells, which was further reduced by PI-103. Additionally, PI-103-treated MO59K cells exhibited an increased expression of the apoptosis marker cleaved PARP and increased subG1 fraction. Moreover, irradiation induced a strong G2 arrest in MO59J cells (~ 80% vs. ~ 50% in MO59K), which was, however, partially reduced in the presence of PI-103. In contrast, treatment with PI-103 increased the G2 fraction in irradiated MO59K cells.

CONCLUSIONS

The triple-target inhibitor PI-103 exerted radiosensitization on MO59K cells, but, unexpectedly, caused radioresistance in the MO59J line, lacking DNA-PK. The difference is most likely due to low expression of the DNA-PK substrate p53 in MO59J cells, which was further reduced by PI-103. This led to less apoptosis as compared to drug-free MO59J cells and enhanced survival via partially abolished cell-cycle arrest. The findings suggest that the lack of DNA-PK-dependent NHEJ in MO59J line might be compensated by DNA-PK independent DSB repair via a yet unknown mechanism.

γH2AX foci assay in glioblastoma: Surgical specimen versus corresponding stem cell culture

AIM

To assess radiation response using γH2AX assay in surgical specimens from glioblastoma (GB) patients and their corresponding primary gliosphere culture. To test the hypothesis that gliospheres (stem cell enriched) are more resistant than specimens (bulky cell dominated) but that the interpatient heterogeneity is similar.

MATERIAL AND METHODS

Ten pairs of specimens and corresponding gliospheres derived from patients with IDH-wildtype GB were studied. Specimens and gliospheres were irradiated with graded doses and after 24 h the number of residual γH2AX foci was counted.

RESULTS

Gliospheres showed a higher Nestin expression than specimens and exhibited two different phenotypes: free floating (n = 7) and attached (n = 3). Slope analysis revealed an interpatient heterogeneity with values between 0.15 and 1.30 residual γH2AX foci/Gy. Free-floating spheres were more resistant than their parental specimens (median slope 0.13 foci/Gy versus 0.53) as well as than the attached spheres (2.14). The slopes of free floating spheres did not correlate with their corresponding specimens while a trend for a positive correlation was found for the attached spheres and the respective specimens. Association with MGMT did not reach statistical significance.

CONCLUSION

Consistent with the clinical phenotype and our previous experiments, GB specimens show low radiation sensitivity. Stem-cell enriched free-floating gliospheres were more resistant than specimens supporting the concept of radioresistance in stem cell-like cells. The lack of correlation between specimens and their respective gliosphere cultures needs validation and may have a profound impact on future translational studies using γH2AX as a potential biomarker for personalized radiation therapy.

A heterogeneous cellular response to ionizing radiation revealed by single cell transcriptome sequencing

Our understanding on transcriptional regulation of tumour cells responding to ionizing radiation (IR) has mostly come from bulk sequencing. However, due to the heterogeneity of tumour, how each individual cell responds to IR differently is unclear. We report here a heterogeneous cellular response to IR by single cell transcriptome sequencing. We utilized the barcoded Smart-seq2 single cell transcriptome sequencing technology in breast cancer cell line MDA-MB-231 both without and with IR treatment. To further understand how ATM, a major hub protein required for an optimal DNA damage response, affected the heterogeneous IR response, we also knocked down ATM gene for single cell transcriptome sequencing. Single cell t-SNE analysis showed four clusters of cells responding to IR in distinctive ways: Cluster 1 changed the least; Cluster 2 responded to IR by upregulating ribosome associated genes, while Cluster 4 upregulated both ribosome and G1/S phase associated genes; Cluster 3 was a new cluster, which appeared only in irradiated cells. In the absence of ATM kinase, cells displayed much less transcriptional changes after IR. And Cluster 4 in wild-type cells, which had the greatest change in response to IR, was not present in the ATM knock-down cells. We also selected three IR-induced genes for functional validation in both MDA-MB-231 and an additional breast cancer cell line to demonstrate their importance in radiation sensitivity. Taken together, our single cell transcriptome analysis has revealed a heterogeneous cellular response to DNA damage induced by IR and identified potential biomarkers of radiation sensitivity.

Chaetocin induced chromatin condensation: effect on DNA repair signaling and survival

PURPOSE

The aim of the present study was to evaluate the effect of the histone lysine-methyltransferase (HKMT) inhibitor chaetocin on chromatin structure and its effect on ionizing radiation (IR) induced DNA damage response.

METHODS

Concentration and time-dependent effects of chaetocin on chromatin clustering and its reversibility were analyzed by immunofluorescent assays in the non-small cell lung carcinoma (NSCLC) cell lines H460 and H1299Q4 and in human skin fibroblasts. In addition, IR induced damage response (γH2AX, 53BP1, and pATM foci formation) was studied by immunofluorescent assays. The effect on survival was determined by performing single-cell clonogenic assays.

RESULTS

Chaetocin significantly increased the radiation sensitivity of H460 (F test on nonlinear regression, p < .0011) and of H1299 (p = .0201). In addition, treatment with 15 nM chaetocin also decreased the total radiation doses that control 50% of the plaque monolayers (TCD50) from 17.2 ± 0.3 Gy to 7.3 ± 0.4 Gy (p < .0001) in H1299 cells and from 11.6 ± 0.1 Gy to 6.5 ± 0.3 Gy (p < .0001). Phenotypically, chaetocin led to a time and concentration-dependent clustering of the chromatin in H1299 as well as in fibroblasts, but not in H460 cells. This phenotype of chaetocin induced chromatin clustering (CICC) was reversible and depended on the expression of the HKMTs SUV39H1 and G9a. Treatment with siRNA for SUV39h1 and G9a significantly reduced the CICC phenotype. Immunofluorescent assay results showed that the CICC phenotype was enriched for the heterochromatic marker proteins H3K9me3 and HP1α. γH2AX foci formation was not affected, neither in cells with normal nor with CICC phenotype. In contrast, repair signaling with 53BP1 and pATM foci formation was significantly reduced in the CICC phenotype.

CONCLUSIONS

Treatment with chaetocin increased the radiation sensitivity of cells in vitro and DNA damage response, especially of 53BP1 and ATM-dependent repair by affecting chromatin structure. The obtained results support the potential use of natural HKMT inhibitors such as chaetocin or other bioactive compounds in improving radiosensitivity of cancer cells.

Analysis of chromosomal aberrations and γH2A.X foci to identify radiation-sensitive ataxia-telangiectasia patients

Ataxia-telangiectasia (AT) is a rare inherited recessive disorder which is caused by a mutated Ataxia-telangiectasia mutated (ATM) gene. Hallmarks include chromosomal instability, cancer predisposition and increased sensitivity to ionizing radiation. The ATM protein plays an important role in signaling of DNA double-strand breaks (DSB), thereby phosphorylating the histone H2A.X. Non-functional ATM protein leads to defects in DNA damage response, unresolved DSBs and genomic instability. The aim of this study was to evaluate chromosomal aberrations and γH2A.X foci as potential radiation sensitivity biomarkers in AT patients. For this purpose, lymphocytes of 8 AT patients and 10 healthy controls were irradiated and induced DNA damage and DNA repair capacity were detected by the accumulation of γH2A.X foci. The results were heterogeneous among AT patients. Evaluation revealed 2 AT patients with similar γH2A.X foci numbers as controls after 1 h while 3 patients showed a lower induction. In regard to DNA repair, 3 of 5 AT patients showed poor damage repair. Therefore, DNA damage induction and DNA repair as detected by H2A.X phosphorylation revealed individual differences, seems to depend on the underlying individual mutation and thus appears not well suited as a biomarker for radiation sensitivity. In addition, chromosomal aberrations were analyzed by mFISH. An increased frequency of spontaneous chromosomal breakage was characteristic for AT cells. After irradiation, significantly increased rates for non-exchange aberrations, translocations, complex aberrations and dicentric chromosomes were observed in AT patients compared to controls. The results of this study suggested, that complex aberrations and dicentric chromosomes might be a reliable biomarker for radiation sensitivity in AT patients, while non-exchange aberrations and translocations identified both, spontaneous and radiation-induced chromosomal instability.

MAPK4 deletion enhances radiation effects and triggers synergistic lethality with simultaneous PARP1 inhibition in cervical cancer

BACKGROUND

Cervical cancer is one of the most common cancers among females worldwide and advanced patients have extremely poor prognosis. However, adverse reactions and accumulating resistance to radiation therapy require further investigation.

METHODS

The expression levels of mitogen-activated protein kinase 4 (MAPK4) mRNA were analyzed by real-time PCR and its association with overall survival was analyzed using Kaplan-Mier method. Colony formation, immunofluorescence and western blotting were used to examine the effects of MAPK4 knockout or over-expression on cervical cancer cells after radiation treatment. Drug-sensitivity of cervical cancer cells to PARP1 inhibitors, olaparib or veliparib, was analyzed by CCK-8 cell viability assays, and the 50% inhibitory concentration (IC50) was quantified using GraphPad Prism. The functional effects of MAPK4 knockout on the sensitivity of cervical cancer to radiation treatment and PARP1 inhibitors were further examined using xenograft tumor mouse models in vivo.

RESULTS

Cervical cancer patients with high MAPK4 mRNA expression have lower survival rate. After radiation treatment, the colony number of MAPK4 knockout cells was markedly reduced, and the markers for DNA double-chain breakage were significantly up-regulated. In addition, MAPK4 knockout reduced protein kinase B (AKT) phosphorylation, whereas its over-expression resulted in opposite effects. In MAPK4 KO cells with irradiation treatment, inhibition of AKT phosphorylation promoted DNA double-chain breakage. Constitutive activation of AKT (CA-AKT) increased the levels of phosphorylated-AKT (p-AKT), and DNA repair-related proteins, phosphorylated-DNA-dependent protein kinase (p-DNA-PK) and RAD51 recombinase (RAD51). Furthermore, MAPK4 knockout was found to affect the sensitivity of cervical cancer cells to poly ADP-ribose polymerase 1 (PARP1) inhibitors by activating the phosphorylation of AKT. Moreover, in vivo results demonstrated that MAPK4 knockout enhanced the sensitivity of cervical cancer to radiation and PARP1 inhibitors in mouse xenograft models.

CONCLUSIONS

Collectively, our data suggest that combined application of MAPK4 knockout and PARP1 inhibition can be used as therapeutic strategy in radiation treatment for advanced cervical carcinoma.

Individual response of humans to ionising radiation: governing factors and importance for radiological protection

Tissue reactions and stochastic effects after exposure to ionising radiation are variable between individuals but the factors and mechanisms governing individual responses are not well understood. Individual responses can be measured at different levels of biological organization and using different endpoints following varying doses of radiation, including: cancers, non-cancer diseases and mortality in the whole organism; normal tissue reactions after exposures; and, cellular endpoints such as chromosomal damage and molecular alterations. There is no doubt that many factors influence the responses of people to radiation to different degrees. In addition to the obvious general factors of radiation quality, dose, dose rate and the tissue (sub)volume irradiated, recognized and potential determining factors include age, sex, life style (e.g., smoking, diet, possibly body mass index), environmental factors, genetics and epigenetics, stochastic distribution of cellular events, and systemic comorbidities such as diabetes or viral infections. Genetic factors are commonly thought to be a substantial contributor to individual response to radiation. Apart from a small number of rare monogenic diseases such as ataxia telangiectasia, the inheritance of an abnormally responsive phenotype among a population of healthy individuals does not follow a classical Mendelian inheritance pattern. Rather it is considered to be a multi-factorial, complex trait.

53BP1 expression and immunoscore are associated with the efficacy of neoadjuvant chemoradiotherapy for rectal cancer

PURPOSE

Considering the effects of P53 binding protein 1 (53BP1) expression and T lymphocyte infiltration density on tumor radiosensitivity, we investigated the relation of 53BP1 expression and immunoscore based on T lymphocyte infiltration density with the efficacy of neoadjuvant chemoradiotherapy (CRT) for rectal cancer.

METHODS

Fifty-five patients with rectal cancer receiving neoadjuvant CRT followed by surgery were enrolled. The 53BP1 expression level and the density of CD3⁺, CD8⁺, and CD45RO⁺ T lymphocytes in the tumor tissues were examined by immunohistochemistry, and the relation of these findings to the rates of tumor regression, disease-free survival (DFS), and overall survival (OS) was analyzed.

RESULTS

The levels of 53BP1 and the CD3/CD8 immunoscore were closely correlated with the response to CRT (p < 0.05), with an area under the receiver operating characteristic curve for CRT efficacy prediction of 0.626 and 0.717, respectively. Further survival analysis revealed that high 53BP1 expression effectively prolonged 2‑year DFS compared with low 53BP1 expression (87.5% [95%CI 77.3-97.7] vs. 53.3% [95%CI 28.1-78.6]; p < 0.05), while the effect of immunoscore on survival was restricted by the expression status of 53BP1. Cox multivariate analysis confirmed 53BP1 as an independent prognostic factor in DFS.

CONCLUSION

The pretreatment levels of 53BP1 and the immunoscore based on CD3⁺/CD8⁺ T cell infiltration density in tumor tissues are effective predictors for the CRT response, and 53BP1 has a more pronounced impact on prognosis.

A bidirectional effect of Rac1 inhibition-Protects radiation-induced intestinal injury while inhibits tumor

AIMS

To investigate whether Rac1 inhibition can alleviate radiation-induced intestinal injury (RIII), meanwhile exist no protection on tumors.

MATERIALS AND METHODS

Rac1 inhibition was achieved by its specific inhibitor, NSC23766. Mice were pretreated with different intraperitoneal injections, which were normal saline for NS group (N = 9), and 2.5 mg/kg and 5 mg/kg of NSC23766 for Low-Dose group (N = 9) and High-Dose group (N = 9), respectively. After total body irritation (10Gy), small intestinal tissues were collected for Hematoxylin-Eosin (H&E) staining and Terminal-deoxynucleotidyl Transferase Mediated dUTP Nick End Labeling (TUNEL). Intestinal epithelial and tumor cell lines, namely MODE-k and CT-26, were used to further study the role of Rac1 inhibition on radiation damage. Flow cytometry was used to detect changes in reactive oxygen species production, cell cycles and mitochondrial membrane potential, the latter was also checked by fluorescence microscope. Changes of protein-expression associated with apoptosis and cell cycles were detected by Western blotting to explain the possible molecular mechanism.

KEY FINDINGS

Height of intestine villi and depth of crypt were higher (P < 0.01) and apoptosis ratio lower (P < 0.01) in High-Dose group compared with those in NS group. After radiation, Rac1 inhibition pre-treatment improved the vitality (P < 0.01) and reduced the apoptosis (P < 0.01) in MODE-k while yielded opposite results in CT-26, and reduced ROS production of MODE-k (P < 0.01) while had little effect on that of CT-26. Rac1 inhibition differently affected the cell cycles of normal cells and that of tumor cells.

SIGNIFICANCE

Inhibition of Rac1 could alleviate RIII, meanwhile assist the killing effect of radiation on tumor cells.

Development of a high-throughput γ-H2AX assay based on imaging flow cytometry

Background

Measurement of γ-H2AX foci levels in cells provides a sensitive and reliable method for quantitation of the radiation-induced DNA damage response. The objective of the present study was to develop a rapid, high-throughput γ-H2AX assay based on imaging flow cytometry (IFC) using the ImageStream®^X Mk II (ISX) platform to evaluate DNA double strand break (DSB) repair kinetics in human peripheral blood cells after exposure to ionizing irradiation.

Methods

The γ-H2AX protocol was developed and optimized for small volumes (100 μL) of human blood in Matrix™ 96-tube format. Blood cell lymphocytes were identified and captured by ISX INSPIRE™ software and analyzed by Data Exploration and Analysis Software.

Results

Dose- and time-dependent γ-H2AX levels corresponding to radiation exposure were measured at various time points over 24 h using the IFC system. γ-H2AX fluorescence intensity at 1 h after exposure, increased linearly with increasing radiation dose (R² = 0.98) for the four human donors tested, whereas the dose response for the mean number of γ-H2AX foci/cell was not as robust (R² = 0.81). Radiation-induced γ-H2AX levels rapidly increased within 30 min and reached a maximum by ~ 1 h, after which time there was fast decline by 6 h, followed by a much slower rate of disappearance up to 24 h. A mathematical approach for quantifying DNA repair kinetics using the rate of γ-H2AX decay (decay constant, K_dec), and yield of residual unrepaired breaks (F_res) demonstrated differences in individual repair capacity between the healthy donors.

Conclusions

The results indicate that the IFC-based γ-H2AX protocol may provide a practical and high-throughput platform for measurements of individual global DNA DSB repair capacity which can facilitate precision medicine by predicting individual radiosensitivity and risk of developing adverse effects related to radiotherapy treatment.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1344-7) contains supplementary material, which is available to authorized users.

Potential screening assays for individual radiation sensitivity and susceptibility and their current validation state

Purpose: The workshop on 'Individual Radiosensitivity and Radiosusceptibility' organized by MELODI and CONCERT on Malta in 2018, evaluated the current state of assays to identify sensitive and susceptible subgroups. The authors provide an overview on potential screening assays detecting individuals showing moderate to severe early and late radiation reactions or are at increased risk to develop cancer upon radiation exposure.Conclusion: It is necessary to separate clearly between tissue reactions and stochastic effects such as cancer when comparing the existing literature to validate various test systems. Requirements for the assays are set up. The literature is reviewed for assays that are reliable and robust. Sensitivity and specificity of the assays are regarded and scrutinized for modifying factors. Accuracy of an assay system is required to be more than 90% to balance risks of adverse reactions against risk to fail to cure the cancer. No assay/biomarker is in routine use. Assays that have shown predictive potential for radiosensitivity include SNPs, the RILA assay, and the pATM assay. A tree of risk guideline for radiologists is provided to assist medical treatment decisions. Recommendations for effective research include the setup of common retrospective and prospective cohorts/biobanks to validate current and future tests.

Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells

Background

Most tumor cells show aberrantly activated Akt which leads to increased cell survival and resistance to cancer radiotherapy. Therefore, targeting Akt can be a promising strategy for radiosensitization. Here, we explore the impact of the Akt inhibitor MK-2206 alone and in combination with the dual PI3K and mTOR inhibitor PI-103 on the radiation sensitivity of glioblastoma cells. In addition, we examine migration of drug-treated cells.

Methods

Using single-cell tracking and wound healing migration tests, colony-forming assay, Western blotting, flow cytometry and electrorotation we examined the effects of MK-2206 and PI-103 and/or irradiation on the migration, radiation sensitivity, expression of several marker proteins, DNA damage, cell cycle progression and the plasma membrane properties in two glioblastoma (DK-MG and SNB19) cell lines, previously shown to differ markedly in their migratory behavior and response to PI3K/mTOR inhibition.

Results

We found that MK-2206 strongly reduces the migration of DK-MG but only moderately reduces the migration of SNB19 cells. Surprisingly, MK-2206 did not cause radiosensitization, but even increased colony-forming ability after irradiation. Moreover, MK-2206 did not enhance the radiosensitizing effect of PI-103. The results appear to contradict the strong depletion of p-Akt in MK-2206-treated cells. Possible reasons for the radioresistance of MK-2206-treated cells could be unaltered or in case of SNB19 cells even increased levels of p-mTOR and p-S6, as compared to the reduced expression of these proteins in PI-103-treated samples. We also found that MK-2206 did not enhance IR-induced DNA damage, neither did it cause cell cycle distortion, nor apoptosis nor excessive autophagy.

Conclusions

Our study provides proof that MK-2206 can effectively inhibit the expression of Akt in two glioblastoma cell lines. However, due to an aberrant activation of mTOR in response to Akt inhibition in PTEN mutated cells, the therapeutic window needs to be carefully defined, or a combination of Akt and mTOR inhibitors should be considered.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5517-4) contains supplementary material, which is available to authorized users.

Salvianolic acid B renders glioma cells more sensitive to radiation via Fis-1-mediated mitochondrial dysfunction

Glioma remains the leading cause of brain tumor-related death worldwide, and radiation is a standard adjuvant therapy with proven efficacy. Salvianolic acid B (SalB), a bioactive compound isolated from Radix Salviae, has been shown to exert anti-cancer effects in many cancer cell lines, including glioma. This study aimed to investigate whether SalB could affect response to radiation in human glioma cells. We found that SalB decreased cell viability of U87 cells in a-dose-dependent manner. A subthreshold dose of SalB at 0.5 μM, which had no effect on cell viability and apoptosis, significantly increased radiation sensitivity of U87 cells in a dose- and time-dependent manner, but had no effect on sensitivity to temozolomide (TMZ). Similar results were also observed in human glioma U373 cells. In addition, SalB aggravated the radiation-induced apoptosis and mitochondrial dysfunction, as measured by mitochondrial Ca²⁺ buffering capacity and mitochondrial swelling. SalB treatment markedly promoted mitochondrial fission and differently regulated the expression of fission proteins. Furthermore, downregulation of the fission protein Fis-1 using siRNA was found to partially reversed the SalB-induced effects on cell viability, apoptosis and mitochondrial fission in U87 cells. In conclusion, our results suggest that a subthreshold dose of SalB renders glioma cells more sensitive to radiation via Fis-1-mediated mitochondrial dysfunction, and radiotherapy combined with SalB might be a novel treatment for glioma patients.

Radiosensitivity of Lung Metastases by Primary Histology and Implications for Stereotactic Body Radiation Therapy Using the Genomically Adjusted Radiation Dose

INTRODUCTION

We assessed the radiosensitivity of lung metastases on the basis of primary histologic type by using a validated gene signature and model lung metastases for the gnomically adjusted radiation dose (GARD).

METHODS

Tissue samples were identified from our prospective observational protocol. The radiosensitivity index (RSI) 10-gene assay was run on samples and calculated alongside the GARD by using the previously published algorithms. A cohort of 105 patients with 137 lung metastases treated with stereotactic body radiation therapy (SBRT) at our institution was used for clinical correlation.

RESULTS

A total of 138 unique metastatic lung lesions from our institution's tissue biorepository were identified for inclusion. There were significant differences in the RSI of lung metastases on the basis of histology. In order of decreasing radioresistance, the median RSIs for the various histologic types of cancer were endometrial adenocarcinoma (0.49), soft-tissue sarcoma (0.47), melanoma (0.44), rectal adenocarcinoma (0.43), renal cell carcinoma (0.33), head and neck squamous cell cancer (0.33), colon adenocarcinoma (0.32), and breast adenocarcinoma (0.29) (p = 0.002). We modeled the GARD for these samples and identified the biologically effective dose necessary to optimize local control. The 12- and 24-month Kaplan-Meier rates of local control for radioresistant versus radiosensitive histologic types from our clinical correlation cohort after lung SBRT were 92%/87% and 100%, respectively (p = 0.02).

CONCLUSIONS

In this analysis, we have noted significant differences in radiosensitivity on the basis of primary histologic type of lung metastases and have modeled the biologically effective dose necessary to optimize local control. This study suggests that primary histologic type may be an additional factor to consider in selection of SBRT dose to the lung and that dose personalization may be feasible.

Inhibition of MicroRNA-21-5p Promotes the Radiation Sensitivity of Non-Small Cell Lung Cancer Through HMSH2

BACKGROUND

This study aimed to explore the effects of microRNA-21-5p (miR-21-5p) on the radiation sensitivity of non-small cell lung cancer (NSCLC) and the involvement of human MutS homolog 2 (hMSH2) One hundred fourteen NSCLC patients at stage II or III who received surgery and postoperative radiotherapy were enrolled in this study.

METHODS

The patients were assigned into radiation-sensitive and -insensitive groups. NSCLC A549 cells were transfected to generate control, Negative control (NC), miR-21-5p inhibitor, miR-21-5p mimic, small interfering hMSH2 (sihMSH2), miR-21-5p inhibitor + sihMSH2 and hMSH2 overexpression groups. Immunohistochemistry was performed to detect the hMSH2 expression in transfected and irradiated cells. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were performed to evaluate A549 miR-21-5p and hMSH2 expression in transfected and irradiated cells. A colony formation assay was adopted for cell survival analysis. The relationship between miR-21-5p and hMSH2 was verified by a luciferase reporter assay. Cell viability was measured by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and apoptosis was assessed by flow cytometry. NSCLC nude mouse models were established, and tumor volumes and tumor weights were recorded.

RESULTS

The radiation-sensitive group of patients exhibited lower miR-21-5p but higher hMSH2 expression than the insensitive group. For irradiated A549 cells, lower cell survival, higher apoptosis, increased miR-21-5p expression and decreased hMSH2 expression were observed at 6 and 8 Gy than at 0, 2 and 4 Gy; compared to 6 Gy, cell survival and hMSH2 expression were decreased and apoptosis and miR-21-5p expression were increased at 8 Gy. Additionally, miR-21-5p was found to target hMSH2. Compared with the control group, the cell survival rate was lower and the apoptosis rate higher in the miR-21-5p inhibitor group, whereas the opposite was observed for the miR-21-5p mimic and sihMSH2 groups. For the mouse model, decreased tumor volume and tumor weight and higher hMSH2 expression were found in the miR-21-5p inhibitor, radiation, hMSH2 overexpression, miR-21-5p inhibitor + radiation and hMSH2 overexpression + radiation groups compared with the control group. In addition, tumor volume and tumor weight were decreased and hMSH2 expression increased in the miR-21-5p inhibitor + radiation and hMSH2 overexpression + radiation groups compared with the radiation alone group.

CONCLUSION

These findings indicate that inhibition of miR-21 can promote the radiation sensitivity of NSCLC by targeting hMSH2.

Oleuropein enhances radiation sensitivity of nasopharyngeal carcinoma by downregulating PDRG1 through HIF1α-repressed microRNA-519d

Background

Oleuropein (OL) is a well-known anti-oxidative agent and is shown to reduce the hypoxia-inducible factor 1 α (HIF1α) protein expression after radiation. The current study investigated the effects of OL on radiation response in nasopharyngeal carcinoma (NPC).

Methods

Colony formation assay was performed to compare the radiation response in vitro. Xenograft mouse model was used to study the OL effects on radiation in vivo. Chromatin immunoprecipitation and luciferase reporter assays were performed to identify the relations among HIF1α, miR-519d and PDRG1. Stable HIF1α or PDRG1 overexpression, and miR-519d downregulation were performed to test the radiation response both in vitro and in vivo.

Results

OL strongly enhanced radiosensitivity of NPC cells both in vitro and in vivo. Chromatin immunoprecipitation and luciferase reporter assays suggested miR-519d was a direct target of HIF1α, and PDRG1 was a direct target of miR-519d. Overexpression of HIF1α or PDRG1, and downregulation of miR-519d abolished the radiation sensitizing effects of OL.

Conclusion

Our study hereby demonstrates OL is a radiation sensitizing agent in NPC both in vivo and in vitro. OL treatment reduces the activity of HIF1α-miR-519d-PDRG1 pathway, which is essential to the radiosensitizing effects of OL.

Influence of iodine supply on the radiation-induced DNA-fragmentation

The protective effect of stable iodide against radiation on thyroid cells was investigated. One physiological effect of stable iodine is well-rooted: stable iodine leads to a reduced thyroid uptake of radioactive iodine. This work wants to focus on an intrinsic effect of stable iodine by which DNA-damage in cells is prevented. To investigate this intrinsic effect thyroid cells (FRTL-5) were externally irradiated by use of a linear accelerator (LINAC) applying energy doses of 0.01 Gy-400 Gy and by incubation with various activity concentrations of ¹³¹I (0.1-50 MBq/ml for 24 h). We added stable iodine (NaI) to the cells prior to external irradiation and investigated the effect of the concentration of stable iodine (1, 5, 15 μg/ml). In order to clarify whether thyroid cells have a distinctive and iodine-dependent reaction to ionizing radiation, keratinocytes (HaCaT) without NIS were exposed in the same way. As indicators for the cellular reaction, the extent of DNA fragmentation was determined (Roche, Mannheim, Germany). Both cell types showed distinct ability for apoptosis as proven with camptothecin. The addition of "cold" iodine from 1 to 15 μg/ml without irradiation ("negative control") did not change the response in both cell types. Plausibly, the radio-sensitivity of both cell types did increase markedly with increasing radiation dose but the radiation effect is diminished if iodine is added to the thyroid cells beforehand. The DNA-damage in thyroid cells after addition of cold iodine is reduced by a factor of 2-3. The skin cells did not show an significant change of radio-sensitivity depending on the presence of cold iodine. Elementary iodine possibly acts as a radical scavenger and thus markedly reduces the secondary radiation damage caused by the formation of cytotoxic radicals. This intrinsic radioprotective effect of iodine is seen only in cells with NIS.

Effects of RNAi-mediated TUSC3 silencing on radiation-induced autophagy and radiation sensitivity of human lung adenocarcinoma cell line A549 under hypoxic condition

This study examined the effects of RNAi-mediated TUSC3 silencing on radiation-induced autophagy and radiation sensitivity of human lung adenocarcinoma cell line A549 under hypoxic condition. Different CoCl2 concentrations were used to treat A549 cells and establish a CoCl2-induced hypoxic model of A549 cells. MTT and clone formation assays were used to determine the effects of different concentrations of CoCl2 on the growth and proliferation of A549 cells treated by different doses of X-ray irradiation. The siRNA-expressing vector was transfected by liposomes and for silencing of TUSC3. Flow cytometry was used to measure cell cycle changes and apoptosis rate. Real-time quantitative polymerase chain reaction (qRT-PCR) assay was performed to detect the expression of TUSC3 mRNA. Western blotting was applied to detect the changes of TUSC3, LC3, and p62 proteins under different CoCl2 concentrations and after siRNA silencing of TUSC3. The TUSC3 levels in A549 cells increased under hypoxic conditions in a dose-dependent manner (P < 0.05). Hypoxia inhibited the growth and proliferation of A549 cells and promoted apoptosis (P < 0.05). With an increasing dose of X-ray irradiation, A549 cells showed significantly increased growth and proliferation and decreased apoptosis (P < 0.05). After siRNA-TUSC3 was transfected by liposome, the TUSC3 level was substantially inhibited (P < 0.05). Silencing TUSC3 inhibited A549 cell growth and proliferation after radiotherapy under hypoxic condition, promoted apoptosis, increased G0/G1 phase cells, and reduced S phase cells (all P < 0.05). Hypoxia and radiation along with different CoCl2 concentrations could induce cell autophagy, which increased with concentration and dose, while silencing the TUSC3 gene inhibited autophagy (all P < 0.05). RNAi silencing of TUSC3 inhibited growth and proliferation, while enhanced apoptosis and radiation sensitivity of hypoxic A549 lung adenocarcinoma cells.

Fukushima's lessons from the blue butterfly: A risk assessment of the human living environment in the post-Fukushima era

A series of studies on the pale grass blue butterfly that were carried out to assess the biological effects of the Fukushima nuclear accident teach 3 important lessons. First, it is necessary to have an environmental indicator species, such as the pale grass blue butterfly in Japan, that is common (not endangered), shares a living environment (air, water, and soil) with humans, and is amenable to laboratory experiments. The monitoring of such indicator species before and immediately after a nuclear accident likely reflects acute impacts caused by initial exposure. To assess transgenerational and chronic effects, continuous monitoring over time is encouraged. Second, it is important to understand the actual health status of a polluted region and comprehend the whole picture of the pollution impacts, rather than focusing on the selected effects of radiation alone. In our butterfly experiments, plant leaves from Fukushima were fed to larval butterflies to access whole-body effects, focusing on survival rate and morphological abnormalities (rather than focusing on a specific disease or biochemical marker). Our results revealed that ionizing radiation is unlikely to be the exclusive source of environmental disturbances. Airborne particulate matter from a nuclear reactor, regardless of its radioactivity, is likely equally important. Finally, our butterfly experiments demonstrate that there is considerable variation in sensitivities to nuclear pollution within a single species or even within a local population. Based on these results, it is speculated that high pollution sensitivity in humans may be caused not only by low levels of functional DNA repair enzymes but also by immunological responses to particulate matter in the respiratory tract. These lessons from the pale grass blue butterfly should be integrated in studying future nuclear pollution events and decision making on nuclear and environmental policies at the local and international levels in the postFukushima era. Integr Environ Assess Manag 2016;12:667-672. © 2016 SETAC.

The role of gene mutations and gene products in intestinal tissue reactions from ionising radiation

The response of the intestine to (low linear-energy-transfer) ionising radiation is reviewed regarding the cellular basis to the reactions, the regenerative processes which restore the tissue, and external agents which aid its recovery. In the steady-state, it is generally considered that the crypt cell lineages in both small and large intestine are maintained by a small number of stem cells, but there are differences for example in the composition of their niche residence and in the numbers of transit cell generations. Various cell surface markers are now available to indentify particular lineage cell types. Radiation doses up to 1Gy cause apoptotic stem-cell death in particular locations, at higher doses to >6Gy Lgr5⁺ stem cells are required for normal intestinal recovery, and at >8Gy some crypts are sterilised and the probability of animal death from intestinal injury increases with higher doses. Mutations in repair genes, tumour suppressor genes, and survival genes cause various degrees of stem cell and clonogenic cell radiosensitisation. Recent evidence is suggesting much plasticity in the crypt cell lineage, potentially contributing to flexibility in the hierarchical lineage, clonogen number variations and the sensitisation differences. Knockout mice for many different genes have been used to detect their role in both steady state and in irradiated conditions, expected to lead to further insight to the damage and restorative processes. Many different external agents have been used to ameliorate intestinal reactions, including prostaglandins, interleukins, angiogenic and epithelial growth factors, other cytokines, and intraluminal factors.

Influence on radiosensitivity of lung glandular cancer cells when ERCC1 gene silenced by targeted siRNA

OBJECTIVE

To identify the influence on radiosensitivity of lung glandular cancer cells when excisions repair cross-complementing group1 (ERCC1) gene was silenced by targeted siRNA.

METHODS

siRNA which targeting to ERCC1 and control siRNA was designed and synthesized. The human lung glandular cancer SPC-A-1 cells was transfected. A total of 56 nude mice were divided into two groups, and two kinds of SPC-A-1 cells were transplanted to armpit of right forelimb, to establish the nude mice subcutaneous xenotransplanted tumor model of human lung glandular cancer cells. After the tumor was developed, the nude mice were randomly divided into four groups and accepted different doses of X-Ray radiation, then the change of tumor volume, survival time of mice in every group were recorded and the average lifetime was calculated. Twenty-one days later of X-ray experiment, two mice were taken and killed in each group and the tumors organizations were stripped. The cell apoptosis rate and cell cycle distributions were obtained by FCM (flow cytometry).

RESULTS

The volume of tumor which ERCC1 gene was silenced was less than single irradiation group after X-ray irradiation, and the growth speed was slower and the lifetime of mice was lengthened as well (P < 0.05). The cells apoptosis rate and the rate of G2/M cells which ERCC1 gene was silenced were higher than the same dose control group and the rate of G1 cells were lower, which indicated that the cells could be stopped at G2/M point, the cell proliferation was inhibited, the cell apoptosis was promoted and the radiation sensitivity was improved after the ERCC1 was silenced.

CONCLUSIONS

The radiation sensitivity of lung glandular tumor could be improved after the ERCC1 gene was silenced by siRNA.

Snail-induced epithelial-to-mesenchymal transition of MCF-7 breast cancer cells: systems analysis of molecular changes and their effect on radiation and drug sensitivity

Background

Epithelial-to-mesenchymal transition (EMT) has been associated with the acquisition of metastatic potential and the resistance of cancer cells to therapeutic treatments. MCF-7 breast cancer cells engineered to constitutively express the zinc-finger transcriptional repressor gene Snail (MCF-7-Snail cells) have been previously shown to display morphological and molecular changes characteristic of EMT. We report here the results of a comprehensive systems level molecular analysis of changes in global patterns of gene expression and levels of glutathione and reactive oxygen species (ROS) in MCF-7-Snail cells and the consequence of these changes on the sensitivity of cells to radiation treatment and therapeutic drugs.

Methods

Snail-induced changes in global patterns of gene expression were identified by microarray profiling using the Affymetrix platform (U133 Plus 2.0). The resulting data were processed and analyzed by a variety of system level analytical methods. Levels of ROS and glutathione (GSH) were determined by fluorescent and luminescence assays, and nuclear levels of NF-κB protein were determined by an ELISA based method. The sensitivity of cells to ionizing radiation and anticancer drugs was determined using a resazurin-based cell cytotoxicity assay.

Results

Constitutive ectopic expression of Snail in epithelial-like, luminal A-type MCF-7 cells induced significant changes in the expression of >7600 genes including gene and miRNA regulators of EMT. Mesenchymal-like MCF-7-Snail cells acquired molecular profiles characteristic of triple-negative, claudin-low breast cancer cells, and displayed increased sensitivity to radiation treatment, and increased, decreased or no change in sensitivity to a variety of anticancer drugs. Elevated ROS levels in MCF-7-Snail cells were unexpectedly not positively correlated with NF-κB activity.

Conclusions

Ectopic expression of Snail in MCF-7 cells resulted in morphological and molecular changes previously associated with EMT. The results underscore the complexity and cell-type dependent nature of the EMT process and indicate that EMT is not necessarily predictive of decreased resistance to radiation and drug-based therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2274-5) contains supplementary material, which is available to authorized users.

Clinical significance of joint detection of Smac and Caspase9 protein levels in predicting preoperative chemoradiotherapy sensitivity in patients with rectal cancer

AIM: To evaluate the role of second mitochondria-derived activator of Caspase (Smac) and cysteinyl asparate specific proteinase 9 (Caspase9), alone and in combination, in predicting preoperative chemoradiotherapy sensitivity in patients with rectal carcinoma by investigating the relationship between the expression of Smac and Caspase9 and the pathologic response in patients who have received preoperative chemoradiotherapy.

METHODS: The biopsy specimens before chemoradiotherapy and surgical specimens were obtained from 43 cases of rectal adenocarcinoma who received preoperative chemoradiotherapy from July 2008 to June 2013. Immunohistochemical staining was used to test the protein expression levels of Smac and Caspase9, and the relationship between Smac and Caspase9 protein expression levels and postoperative pathological response was analyzed.

RESULTS: The effective rate of preoperative chemoradiotherapy was as high as 72.1%, and the pathological complete response rate was 30.2%. The expression of Smac and Caspase9 was altered after chemoradiotherapy (P < 0.001 for both). Their expression levels were significantly downregulated after chemoradiotherapy. The effective rate of preoperative chemoradiotherapy was significantly increased in patients who were positive for Caspase9 protein expression (staining score range, 1 to 8) before chemoradiotherapy (P < 0.05). And the effective rate was further increased when Smac and Caspase9 proteins were both positive (P = 0.0002). The survival analysis indicated that chemoradiotherapy response was correlated with the overall survival, and the survival was significantly longer in the response arm than in the non-response arm (P = 0.0193).

CONCLUSION: The positive expression of Caspase9 protein in biopsy specimens before chemoradiotherapy can be a marker for sensitivity to radiation and chemotherapy in patients with rectal cancer. Joint detection of Smac and Caspase9 proteins can be more reliable in predicting the sensitivity to preoperative chemoradiotherapy in rectal cancer patients. The response to chemoradiotherapy is a key factor responsible for patients' prognosis. The joint detection of Smac and Caspase9 can be helpful in screening out patients who are sensitive to preoperative chemoradiation.

Low levels of endogenous or X-ray-induced DNA double-strand breaks activate apoptosis in adult neural stem cells

The embryonic neural stem cell compartment is characterised by rapid proliferation from embryonic day (E)11 to E16.5, high endogenous DNA double-strand break (DSB) formation and sensitive activation of apoptosis. Here, we ask whether DSBs arise in the adult neural stem cell compartments, the sub-ventricular zone (SVZ) of the lateral ventricles and the sub-granular zone (SGZ) of the hippocampal dentate gyrus, and whether they activate apoptosis. We used mice with a hypomorphic mutation in DNA ligase IV (Lig4^Y288C), ataxia telangiectasia mutated (Atm^−/−) and double mutant Atm^−/−/Lig4^Y288C mice. We demonstrate that, although DSBs do not arise at a high frequency in adult neural stem cells, the low numbers of DSBs that persist endogenously in Lig4^Y288C mice or that are induced by low radiation doses can activate apoptosis. A temporal analysis shows that DSB levels in Lig4^Y288C mice diminish gradually from the embryo to a steady state level in adult mice. The neonatal SVZ compartment of Lig4^Y288C mice harbours diminished DSBs compared to its differentiated counterpart, suggesting a process selecting against unfit stem cells. Finally, we reveal high endogenous apoptosis in the developing SVZ of wild-type newborn mice.

Summary: This study shows that endogenous and radiation-induced DNA damage sensitively activates apoptosis in the adult sub-ventricular zone (SVZ). Developmentally regulated apoptosis is shown in the neonatal SVZ.

Immunological markers that predict radiation toxicity

Radiotherapy is a major modality of cancer treatment responsible for a large proportion of cancer that is cured. Radiation exposure induces an inflammatory response which can be influenced by genetic, epigenetic, tumour, health and other factors which can lead to very different treatment outcomes between individuals. Molecules involved in the immunological response provide excellent potential biomarkers for the prediction of radiation-induced toxicity. The known molecular and cellular immunological responses in relation to radiation and the potential to improve cancer treatment are presented in this review. In particular, immunological biomarkers of radiation-induced fibrosis and pneumonitis in cancer radiotherapy patients are discussed.

Silencing of HIF-1α enhances the radiation sensitivity of human glioma growth in vitro and in vivo

Gliomas are the leading cause of cancer-related mortality worldwide, and the incidence is increasing. Because gliomas often become resistant to radiation treatment, it is urgent to develop novel therapeutic methods that are more effective and less toxic than current therapies so as to enhance patient survival and quality of life. Effective enhancement of radiation therapy for gliomas in vivo and in vitro was observed upon silencing of hypoxia-inducible factor 1α (HIF-1α) with RNA interference; this enhancement was related to changes in the cell cycle and apoptosis that were accompanied by modulation of Cdc2, cyclin B1, and Bcl-2 expression. Our data suggest that HIF-1α silencing combined with radiation therapy will increase the therapeutic efficacy of glioma treatment via regulation of cell cycle and apoptosis-related signaling pathways.

MiR-224 expression increases radiation sensitivity of glioblastoma cells

Glioblastoma (GBM) is the most common and highly aggressive primary malignant brain tumor. The intrinsic resistance of this brain tumor limits the efficacy of administered treatment like radiation therapy. In the present study, effect of miR-224 expression on growth characteristics of established GBM cell lines was analyzed. MiR-224 expression in the cell lines as well as in primary GBM tumor tissues was found to be low. Exogenous transient expression of miR-224 using either synthetic mimics or stable inducible expression using doxycycline inducible lentiviral vector carrying miR-224 gene, was found to bring about 30-55% reduction in clonogenic potential of U87 MG cells. MiR-224 expression reduced clonogenic potential of U87 MG cells by 85-90% on irradiation at a dose of 6Gy, a dose that brought about 50% reduction in clonogenic potential in the absence of miR-224 expression. MiR-224 expression in glioblastoma cells resulted in 55-65% reduction in the expression levels of API5 gene, a known target of miR-224. Further, siRNA mediated down-regulation of API5 was also found to have radiation sensitizing effect on glioblastoma cell lines. Analysis of the Cancer Genome Atlas data showed lower miR-224 expression levels in male GBM patients to correlate with poorer survival. Higher expression levels of miR-224 target API5 also showed significant correlation with poorer survival of GBM patients. Up-regulation of miR-224 or down-regulation of its target API5 in combination with radiation therapy, therefore appear as promising options for the treatment of glioblastoma, which is refractory to the existing treatment strategies.

Genetic factors in individual radiation sensitivity

Cancer risk and radiation sensitivity are often associated with alterations in DNA repair, cell cycle, or apoptotic pathways. Interindividual variability in mutagen or radiation sensitivity and in cancer susceptibility may also be traced back to polymorphisms of genes affecting e.g. DNA repair capacity. We studied possible associations between 70 polymorphisms of 12 DNA repair genes with basal and initial DNA damage and with repair thereof. We investigated DNA damage induced by ionizing radiation in lymphocytes isolated from 177 young lung cancer patients and 169 cancer-free controls. We also sought replication of our findings in an independent sample of 175 families (in total 798 individuals). DNA damage was assessed by the Olive tail moment (OTM) of the comet assay. DNA repair capacity (DRC) was determined for 10, 30 and, 60min of repair. Genes involved in the single-strand-repair pathway (SSR; like XRCC1 and MSH2) as well as genes involved in the double-strand-repair pathway (DSR; like RAD50, XRCC4, MRE11 and ATM) were found to be associated with DNA damage. The most significant association was observed for marker rs3213334 (p=0.005) of XRCC1 with basal DNA damage (B), in both cases and controls. A clear additive effect on the logarithm of OTM was identified for the marker rs1001581 of the same LD-block (p=0.039): BCC=-1.06 (95%-CI: -1.16 to -0.96), BCT=-1.02 (95%-CI: -1.11 to -0.93) and BTT=-0.85 (95%-CI: -1.01 to -0.68). In both cases and controls, we observed significantly higher DNA basal damage (p=0.007) for carriers of the genotype AA of marker rs2237060 of RAD50 (involved in DSR). However, this could not be replicated in the sample of families (p=0.781). An alteration to DRC after 30min of repair with respect to cases was observed as borderline significant for marker rs611646 of ATM (involved in DSR; p=0.055), but was the most significant finding in the sample of families (p=0.009). Our data indicate that gene variation impacts measurably on DNA damage and repair, suggesting at least a partial contribution to radiation sensitivity and lung cancer susceptibility.

Effect of troglitazone on radiation sensitivity in cervix cancer cells

Purpose

Troglitazone (TRO) is a peroxisome proliferator-activated receptor γ (PPARγ) agonist. TRO has antiproliferative activity on many kinds of cancer cells via G1 arrest. TRO also increases Cu²⁺/Zn²⁺-superoxide dismutase (CuZnSOD) and catalase. Cell cycle, and SOD and catalase may affect on radiation sensitivity. We investigated the effect of TRO on radiation sensitivity in cancer cells in vitro.

Materials and Methods

Three human cervix cancer cell lines (HeLa, Me180, and SiHa) were used. The protein expressions of SOD and catalase, and catalase activities were measured at 2-10 µM of TRO for 24 hours. Cell cycle was evaluated with flow cytometry. Reactive oxygen species (ROS) was measured using 2',7'-dichlorofluorescin diacetate. Cell survival by radiation was measured with clonogenic assay.

Results

By 5 µM TRO for 24 hours, the mRNA, protein expression and activity of catalase were increased in all three cell lines. G0-G1 phase cells were increased in HeLa and Me180 by 5 µM TRO for 24 hours, but those were not increased in SiHa. By pretreatment with 5 µM TRO radiation sensitivity was increased in HeLa and Me180, but it was decreased in SiHa. In Me180, with 2 µM TRO which increased catalase but not increased G0-G1 cells, radiosensitization was not observed. ROS produced by radiation was decreased with TRO.

Conclusion

TRO increases radiation sensitivity through G0-G1 arrest or decreases radiation sensitivity through catalase-mediated ROS scavenging according to TRO dose or cell types. The change of radiation sensitivity by combined with TRO is not dependent on the PPARγ expression level.

Fenofibrate decreases radiation sensitivity via peroxisome proliferator-activated receptor α-mediated superoxide dismutase induction in HeLa cells

Purpose

The fibrates are ligands for peroxisome proliferator-activated receptor (PPAR) α and used clinically as hypolipidemic drugs. The fibrates are known to cause peroxisome proliferation, enhance superoxide dismutase (SOD) expression and catalase activity. The antioxidant actions of the fibrates may modify radiation sensitivity. Here, we investigated the change of the radiation sensitivity in two cervix cancer cell lines in combination with fenofibrate (FF).

Materials and Methods

Activity and protein expression of SOD were measured according to the concentration of FF. The mRNA expressions were measured by using real time reverse-transcription polymerase chain reaction. Combined cytotoxic effect of FF and radiation was measured by using clonogenic assay.

Results

In HeLa cells total SOD activity was increased with increasing FF doses up to 30 µM. In the other hand, the catalase activity was increased a little. As with activity the protein expression of SOD1 and SOD2 was increased with increasing doses of FF. The mRNAs of SOD1, SOD2, PPARα and PPARγ were increased with increasing doses of FF. The reactive oxygen species (ROS) produced by radiation was decreased by preincubation with FF. The surviving fractions (SF) by combining FF and radiation was higher than those of radiation alone. In Me180 cells SOD and catalase activity were not increased with FF. Also, the mRNAs of SOD1, SOD2, and PPARα were not increased with FF. However, the mRNA of PPARγ was increased with FF.

Conclusion

FF can reduce radiation sensitivity by ROS scavenging via SOD induction in HeLa. SOD induction by FF is related with PPARα.