DNA Double-Strand Break Response and Repair Gene Polymorphisms May Influence Therapy Results and Prognosis in Head and Neck Cancer Patients

Radiotherapy and cisplatin-based chemotherapy belong to the main treatment modalities for head and neck squamous cell carcinoma (HNSCC) and induce cancer cell death by generating DNA damage, including the most severe double-strand breaks (DSBs). Alterations in DSB response and repair genes may affect individual DNA repair capacity and treatment sensitivity, contributing to the therapy resistance and poor prognosis often observed in HNSCC. In this study, we investigated the association of a panel of single-nucleotide polymorphisms (SNPs) in 20 DSB signaling and repair genes with therapy results and prognosis in 505 HNSCC patients treated non-surgically with DNA damage-inducing therapies. In the multivariate analysis, there were a total of 14 variants associated with overall, locoregional recurrence-free or metastasis-free survival. Moreover, we identified 10 of these SNPs as independent predictors of therapy failure and unfavorable prognosis in the whole group or in two treatment subgroups. These were MRE11 rs2155209, XRCC5 rs828907, RAD51 rs1801321, rs12593359, LIG4 rs1805388, CHEK1 rs558351, TP53 rs1042522, ATM rs1801516, XRCC6 rs2267437 and NBN rs2735383. Only CHEK1 rs558351 remained statistically significant after correcting for multiple testing. These results suggest that specific germline variants related to DSB response and repair may be potential genetic modifiers of therapy effects and disease progression in HNSCC treated with radiotherapy and cisplatin-based chemoradiation.

DNA Repair Genes Polymorphisms: Impact on Acute Myeloid Leukemia Patients Outcome

BACKGROUND

ATM; XRCC6 and LIG4 genes play an important role in repairing the double-strand DNA breaks and maintaining the genome stability. Single nucleotide polymorphisms (SNPs) in these genes could affect these genes expression and function. The aim of this study was to address the effect of SNP of the DNA repairing genes on corresponding  gene expression as well as AML patient's outcome.

SUBJECTS AND METHODS

This is cross sectional study included 95 newly diagnosed AML patients. For all subjects included in our study SNPs  and expression of ATM (rs189037G>A), XRCC6 (rs2267437C>G) and LIG4 (rs1805388C>T) genes were evaluated by RFLP and real time PCR.

RESULTS

The following SNPs in ATM (AA); XRCC6 (GG); and LIG4 (TT) are associated with down regulation of the corresponding genes (P<0.001). The lower expression of ATM and LIG4 genes are associated with shorter OS and DFS. Cox regression multivariate analysis revealed that lower expression of ATM HR : 2.02 (CI: 1.12-3.64; p=0.020.

CONCLUSION

The following SNPs of ATM (AA); XRCC6 (GG); and LIG4 (TT) are associated with down regulation of corresponding genes expression. ATM and XRCC6 lower expression are predictors of OS while ATM is predictor of DFS and could be used for optimizing the AML therapy.

The roles of risk model based on the 3-XRCC genes in lung adenocarcinoma progression

Background

The abnormal expression of deoxyribonucleic acid (DNA) repair genes might be the cause of tumor development and resistance of malignant cells to chemotherapeutic drugs. A risk model based on the X-ray repair of cross-complementary (XRCC) genes was constructed to improve the diagnosis and treatment of lung adenocarcinoma (LUAD) patients.

Methods

The expression levels, diagnostic values, and prognostic values of XRCC genes were identified, and the roles and regulatory mechanisms of the risk model based on the XRCC4/5/6 in LUAD progression was explored via The Cancer Genome Atlas (TCGA) and Oncomine databases.

Results

XRCC1/2/3/4/5/6, XRCC7 (PRKDC), and XRCC9 (FANCG) were overexpressed, and had diagnostic value for LUAD. The XRCC genes were involved in DNA repair, and participated in the regulation of non-homologous end-joining, homologous recombination, etc. The overall survival (OS), tumor (T) stage, and survival status of patients were significantly different between the Cluster1 and Cluster2 groups. XRCC4/5/6 were independent risk factors affecting the prognosis of LUAD patients. The risk score was related to the prognosis, sex, clinical stage, T, lymph node (N), and metastasis (M) stage, as well as the survival status of LUAD patients. The clinical stage and risk score were independent risk factors for poor prognosis in LUAD patients. The risk model was involved in RNA degradation, cell cycle, basal transcription factors, DNA replication etc. The risk scores were significantly correlated with the expression levels of TGFBR1, CD160, TNFSF4, TNFRSF14, IL6R, CXCL16, TNFRSF25, TAPBP, CCL16, and CCL14.

Conclusions

The risk model based on the XRCC4/5/6 genes could predict the progression of LUAD patients.

PARP6 suppresses the proliferation and metastasis of hepatocellular carcinoma by degrading XRCC6 to regulate the Wnt/β-catenin pathway

PARP6 belongs to the mono-ADP-ribosyltransferase family and has been shown to be involved in the genesis and development of some tumours. However, the role of PARP6 in hepatocellular carcinoma (HCC) development remains to be fully elucidated. In the current study, we demonstrated that PARP6 was expressed at a low level in HCC cells and was negatively related to the degree of tumour differentiation. Additionally, silencing PARP6 led to an increase in the proliferation, invasion and migration ability of HCC cells in both in vitro and in vivo assays. Conversely, an elevation in the PARP6 expression level had the opposite effect. Through gene chip analysis combined with experimental verification, we confirmed that PARP6 can inhibit the expression of XRCC6 by inducing degradation and thus affect the Wnt/β-Catenin signalling pathway, which contributes to the suppression of HCC. Further mechanistic investigation demonstrated that the ubiquitin ligase HDM2 can interact with PARP6 and XRCC6, and mediated the regulatory effect of PARP6 on XRCC6 degradation. Taking together, PARP6 appears to inhibit HCC progression through the XRCC6/Wnt/β-catenin signal axis and could be used as a biomarker for the clinical monitoring of HCC development.

Association between selenium, cadmium, and arsenic levels and genetic polymorphisms in DNA repair genes (XRCC5, XRCC6) in gastric cancerous and non-cancerous tissue

Gastric cancer is one of the most prevalent cancers in northern Iran. The DNA repair genes X-ray repair cross-complementing (XRCC) group 5, XRCC6, which are important members of non-homologous end-joining repair system, play an important role in repairing the DNA double-strand breaks. Chronic exposure to heavy metals has long been recognized as being capable of augmenting gastric cancer incidence among exposed human populations. Since trace elements could directly or indirectly damage DNA, and polymorphism in DNA DSBs-repair genes can alter the capacity of system repair, we assumed that XRCC5 VNTR and XRCC6-61C >G polymorphism also impress the DSBs-repair system ability and contribute to gastric cancer. Therefore, the objective of this research was to evaluate the tissue accumulation of Selenium (Se), Cadmium (Cd) and Arsenic (As), and XRCC5 VNTR, XRCC6-61C >G polymorphisms in cancerous and non-cancerous tissues in Golestan province. The study population included 46 gastric cancer patients and 43 cancer-free controls. Two polymorphisms of XRCC5, XRCC6 were genotyped using polymerase chain reaction (PCR) or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Further employed was atomic absorption spectroscopy so as to determine the levels of Se, Cd and As. Finally, the data were analyzed by SPSS (version 16) statistical software. The Se level was significantly higher in tumors as compared to non-tumor tissues, but there was no significant correlation between As and Cd in cancerous and noncancerous tissues. Allele frequencies of the selected genes were not statistically different between groups regarding XRCC6 (-61C>G). XRCC5 0R/0R, 0R/1R, 1R/1R, and 0R/2R genotypes were more common in cancerous group. High levels of Se in cancerous tissues vs. non-cancerous tissues may be one of the carcinogenic factors; in Golestan province, unlike other regions of Iran and the world, the level of Se is high, hence the higher risks of gastric cancer.

The interaction of adenovirus E1A with the mammalian protein Ku70/XRCC6

Human adenovirus infects terminally differentiated cells and to replicate it must induce S-phase. The chief architects that drive adenovirus-infected cells into S-phase are the E1A proteins, with 5 different isoforms expressed during infection. E1A remodels the infected cell by associating with cellular factors and modulating their activity. The C-terminus of E1A is known to bind to only a handful of proteins. We have identified a novel E1A C-terminus binding protein, Ku70 (XRCC6), which was found to bind directly within the CR4 of E1A from human adenovirus type 5. Depletion of Ku70 reduced virus growth, possibly by activating the DNA damage response pathway. Ku70 was found to localize to viral replication centers and associate with the viral genome. Ku70 was also recruited to cellular cell cycle regulated promoters following viral infection. Our study has identified, for the first time, Ku70 as a novel E1A-binding protein which affects virus life cycle.

The proteomic investigation reveals interaction of mdig protein with the machinery of DNA double-strand break repair

To investigate how mineral dust-induced gene (mdig, also named as mina53, MINA, or NO52) promotes carcinogenesis through inducing active chromatin, we performed proteomics analyses for the interacting proteins that were co-immunoprecipitated by anti-mdig antibody from either the lung cancer cell line A549 cells or the human bronchial epithelial cell line BEAS-2B cells. On SDS-PAGE gels, three to five unique protein bands were consistently observed in the complexes pulled-down by mdig antibody, but not the control IgG. In addition to the mdig protein, several DNA repair or chromatin binding proteins, including XRCC5, XRCC6, RBBP4, CBX8, PRMT5, and TDRD, were identified in the complexes by the proteomics analyses using both Orbitrap Fusion and Orbitrap XL nanoESI-MS/MS in four independent experiments. The interaction of mdig with some of these proteins was further validated by co-immunoprecipitation using antibodies against mdig and its partner proteins, respectively. These data, thus, provide evidence suggesting that mdig accomplishes its functions on chromatin, DNA repair and cell growth through interacting with the partner proteins.

High Expression of XRCC6 Promotes Human Osteosarcoma Cell Proliferation through the β-Catenin/Wnt Signaling Pathway and Is Associated with Poor Prognosis

Increasing evidences show that XRCC6 (X-ray repair complementing defective repair in Chinese hamster cells 6) was upregulated and involved in tumor growth in several tumor types. However, the correlation of XRCC6 and human osteosarcoma (OS) is still unknown. This study was conducted with the aim to reveal the expression and biological function of XRCC6 in OS and elucidate the potential mechanism. The mRNA expression level of XRCC6 was measured in osteosarcoma cells and OS samples by quantitative transcription-PCR (qRT-PCR). The expression of XRCC6 protein was measured using Western blot and immunohistochemical staining in osteosarcoma cell lines and patient samples. Cell Counting Kit 8 (CCK8), colony-forming and cell cycle assays were used to test cell survival capacity. We found that XRCC6 was overexpressed in OS cells and OS samples compared with the adjacent non-tumorous samples. High expression of XRCC6 was correlated with clinical stage and tumor size in OS. Reduced expression of XRCC6 inhibits OS cell proliferation through G2/M phase arrest. Most importantly, further experiments demonstrated that XRCC6 might regulate OS growth through the β-catenin/Wnt signaling pathway. In conclusion, these findings indicate that XRCC6 exerts tumor-promoting effects for OS through β-catenin/Wnt signaling pathway. XRCC6 may serve as a novel therapeutic target for OS patients.

Gene polymorphism in DNA repair genes XRCC1 and XRCC6 and association with colorectal cancer in Swedish patients

The DNA repair genes XRCC1 and XRCC6 have been proposed to participate in the pathological process of cancer by modulating the DNA repair capacity. This study evaluated the susceptibility of the single-nucleotide polymorphisms (SNPs) XRCC1 (rs25487, G > A) and XRCC6 (rs2267437, C > G) to colorectal cancer (CRC) and their association with clinical parameters in Swedish patients with CRC. Using the TaqMan system, these SNPs were screened in 452 patients and 464 controls. No significant difference in genotype distribution was found between the patients and controls, or any significant association with cancer-specific or disease-free survival in patients. However, we showed that the carriers of allele A in XRCC1 (rs25487, G > A) were connected with a higher risk of disseminated CRC (Odds Ratio = 1.64; 95% Confidence Interval = 1.12-2.41, p = 0.012).

Comprehensive analyses of DNA repair pathways, smoking and bladder cancer risk in Los Angeles and Shanghai

Tobacco smoking is a bladder cancer risk factor and a source of carcinogens that induce DNA damage to urothelial cells. Using data and samples from 988 cases and 1,004 controls enrolled in the Los Angeles County Bladder Cancer Study and the Shanghai Bladder Cancer Study, we investigated associations between bladder cancer risk and 632 tagSNPs that comprehensively capture genetic variation in 28 DNA repair genes from four DNA repair pathways: base excision repair (BER), nucleotide excision repair (NER), non-homologous end-joining (NHEJ) and homologous recombination repair (HHR). Odds ratios (ORs) and 95% confidence intervals (CIs) for each tagSNP were corrected for multiple testing for all SNPs within each gene using pACT and for genes within each pathway and across pathways with Bonferroni. Gene and pathway summary estimates were obtained using ARTP. We observed an association between bladder cancer and POLB rs7832529 (BER) (pACT = 0.003; ppathway = 0.021) among all, and SNPs in XPC (NER) and OGG1 (BER) among Chinese men and women, respectively. The NER pathway showed an overall association with risk among Chinese males (ARTP NER p = 0.034). The XRCC6 SNP rs2284082 (NHEJ), also in LD with SREBF2, showed an interaction with smoking (smoking status interaction pgene = 0.001, ppathway = 0.008, poverall = 0.034). Our findings support a role in bladder carcinogenesis for regions that map close to or within BER (POLB, OGG1) and NER genes (XPC). A SNP that tags both the XRCC6 and SREBF2 genes strongly modifies the association between bladder cancer risk and smoking.

Predictive role of XRCC5/XRCC6 genotypes in digestive system cancers

Cancers are a worldwide concern; oral, esophageal and gastrointestinal cancers represent important causes of cancer-related mortality and contribute to a significant burden of human health. The DNA repair systems are the genome caretakers, playing a critical role in the initiation and progression of cancers. However, the association between the genomic variations of DNA repair genes and cancer susceptibility is not well understood. This review focuses on the polymorphic genotypes of the non-homologous end-joining DNA repair system, highlighting the role of two genes of this pathway, XRCC5 and XRCC6, in the susceptibility to digestive system cancers and discussing their potential contributions to personalized medicine.