Analyzing association of the XRCC3 gene polymorphism with ovarian cancer risk

Genomic instability in ovarian cancer: Through the lens of single nucleotide polymorphisms

Ovarian cancer (OC) is the deadliest gynecological malignancy among all female reproductive cancers. It is characterized by high mortality rate and poor prognosis. Genomic instability caused by mutations, single nucleotide polymorphisms (SNPs), copy number variations (CNVs), microsatellite instability (MSI), and chromosomal instability (CIN) are associated with OC predisposition. SNPs, which are highly prevalent in the general population, show a greater relative risk contribution, particularly in sporadic cancers. Understanding OC etiology in terms of genetic basis can increase the use of molecular diagnostics and provide promising approaches for designing novel treatment modalities. This will help deliver personalized medicine to OC patients, which may soon be within reach. Given the pivotal impact of SNPs in cancers, the primary emphasis of this review is to shed light on their prevalence in key caretaker genes that closely monitor genomic integrity, viz., DNA damage response, repair, cell cycle checkpoints, telomerase maintenance, and apoptosis and their clinical implications in OC. We highlight the current challenges faced in different SNP-based studies. Various computational methods and bioinformatic tools employed to predict the functional impact of SNPs have also been comprehensively reviewed concerning OC research. Overall, this review identifies that variants in the DDR and HRR pathways are the most studied, implying their critical role in the disease. Conversely, variants in other pathways, such as NHEJ, MMR, cell cycle, apoptosis, telomere maintenance, and PARP genes, have been explored the least.

Exploring homologous recombination repair and base excision repair pathway genes for possible diagnostic markers in hematologic malignancies

Hematologic malignancies (HMs) are a collection of malignant transformations, originating from the cells in the bone marrow and lymphoid organs. HMs comprise three main types; leukemia, lymphoma, and multiple myeloma. Globally, HMS accounts for approximately 10% of newly diagnosed cancer. DNA repair pathways defend the cells from recurrent DNA damage. Defective DNA repair mechanisms such as homologous recombination repair (HRR), nucleotide excision repair (NER), and base excision repair (BER) pathways may lead to genomic instability, which initiates HM progression and carcinogenesis. Expression deregulation of HRR, NER, and BER has been investigated in various malignancies. However, no studies have been reported to assess the differential expression of selected DNA repair genes combinedly in HMs. The present study was designed to assess the differential expression of HRR and BER pathway genes including RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 in blood cancer patients to highlight their significance as diagnostic/ prognostic marker in hematological malignancies. The study cohort comprised of 210 blood cancer patients along with an equal number of controls. For expression analysis, q-RT PCR was performed. DNA damage was measured in blood cancer patients and controls using the comet assay and LORD Q-assay. Data analysis showed significant downregulation of selected genes in blood cancer patients compared to healthy controls. To check the diagnostic value of selected genes, the Area under curve (AUC) was calculated and 0.879 AUC was observed for RAD51 (p < 0.0001) and 0.830 (p < 0.0001) for APEX1. Kaplan-Meier analysis showed that downregulation of RAD51 (p < 0.0001), XRCC3 (p < 0.02), and APEX1 (p < 0.0001) was found to be associated with a significant decrease in survival of blood cancer patients. Cox regression analysis showed that deregulation of RAD51 (p < 0.0001), XRCC2 (p < 0.02), XRCC3 (p < 0.003), and APEX1 (p < 0.00001) was found to be associated with the poor prognosis of blood cancer patients. Comet assay showed an increased number of comets in blood cancer patients compared to controls. These results are confirmed by performing the LORD q-assay and an increased frequency of lesions/Kb was observed in selected genes in cancer patients compared to controls. Our results showed significant downregulation of RAD51, XRCC2, XRCC3, APEX1, FEN1, PARP1, and XRCC1 genes with increased DNA damage in blood cancer patients. The findings of the current research suggested that deregulated expression of HRR and BER pathway genes can act as a diagnostic/prognostic marker in hematologic malignancies.

Association between RAD51, XRCC2 and XRCC3 gene polymorphisms and risk of ovarian cancer: a case control and an in silico study

Homologous recombination (HR) is one of the important mechanisms in repairing double-strand breaks to maintain genomic integrity and DNA stability from the cytotoxic effects and mutations. Various studies have reported that single nucleotide polymorphisms (SNPs) in the HR-associated genes may have a significant association with ovarian cancer (OCa) risk but the results were inconclusive. In the present study, five polymorphisms of HR-associated genes (RAD51, XRCC2 and XRCC3) were genotyped by allelic discrimination assay in 200 OCa cases and 200 healthy individuals. The association with OCa risk was evaluated by unconditional logistic regression analyses. The results revealed that the mutant allele in both rs1801320 (CC) and rs1801321 (TT) of RAD51 gene was associated with increased risk of OCa (odds ratio [OR] 3.79, 95% confidence interval [CI] 1.21-11.78, p = 0.014 and OR 1.61, 95% CI 1.06-2.45, p = 0.025, respectively). Moreover, a significant association of TT allele (OR 4.68, 95% CI 1.27-17.15, p = 0.011) of rs3218536 of XRCC2 gene with OCa was observed. Stratified analysis results showed that patients with early menarche and stages 3 and 4 were found to be associated with rs1801321 of RAD51 gene and rs1799794 of XRCC3 gene. In silico analysis predicted that the two missense SNPs (rs3218536 and rs1799794) were found to have an impact on the protein structure, stability and function. The present study suggested that RAD51 and XRCC2 gene polymorphisms might have an impact on the OCa risk in the South Indian population. However, studies with a larger sample and on different populations are needed to support the conclusions.

The association between XRCC3 rs1799794 polymorphism and cancer risk: a meta-analysis of 34 case-control studies

BACKGROUND

Studies on the XRCC3 rs1799794 polymorphism show that this polymorphism is involved in a variety of cancers, but its specific relationships or effects are not consistent. The purpose of this meta-analysis was to investigate the association between rs1799794 polymorphism and susceptibility to cancer.

METHODS

PubMed, Embase, the Cochrane Library, Web of Science, and Scopus were searched for eligible studies through June 11, 2019. All analyses were performed with Stata 14.0. Subgroup analyses were performed by cancer type, ethnicity, source of control, and detection method. A total of 37 studies with 23,537 cases and 30,649 controls were included in this meta-analysis.

RESULTS

XRCC3 rs1799794 increased cancer risk in the dominant model and heterozygous model (GG + AG vs. AA: odds ratio [OR] = 1.04, 95% confidence interval [CI] = 1.00-1.08, P = 0.051; AG vs. AA: OR = 1.05, 95% CI = 1.00-1.01, P = 0.015). The existence of rs1799794 increased the risk of breast cancer and thyroid cancer, but reduced the risk of ovarian cancer. In addition, rs1799794 increased the risk of cancer in the Caucasian population.

CONCLUSION

This meta-analysis confirms that XRCC3 rs1799794 is related to cancer risk, especially increased risk for breast cancer and thyroid cancer and reduced risk for ovarian cancer. However, well-designed large-scale studies are required to further evaluate the results.

Polymorphism of XRCC3 in Egyptian Breast Cancer Patients

Purpose

Polymorphisms of DNA repair genes may contribute to variations in DNA repair capacity and subsequent genetic susceptibility to different cancers. In Egypt, breast cancer is the most common cancer among women, representing 18.9% of the total cancer cases. The present study assesses the correlation between X-ray repair cross-complementing group 3 (XRCC3) polymorphism with breast cancer and treatment response in Egyptian female breast cancer patients.

Patients and Methods

This pilot case–control study was conducted on 66 female breast cancer patients and 20 apparently healthy females as a control group. Tumor grading, immunohistostaining of hormone (progesterone and estrogen) receptors and human epidermal growth factor receptor 2 (HER2), and RFLP-PCR for XRCC3 (rs861539) polymorphism were performed. All breast cancer patients received a treatment protocol (after surgery) which was either chemotherapy (anthracyclines followed by paclitaxel or anthracyclines + fluorouracil) or radiotherapy, or both. Disease-free survival (DFS) and overall survival (OS) were recorded.

Results

The number of patients with a heterozygous allele (GA) was significantly higher in cases of tumor size >20 mm. The A allele was correlated with younger age at diagnosis in both chemotherapy and radiotherapy groups. Poor treatment response and higher mortality rates were significantly associated with AA and GA compared with GG alleles (normal allele). In the chemotherapy group, out of eight patients with the A allele, six showed a poor response to treatment containing fluorouracil.

Conclusion

XRCC3 rs861539 polymorphism could be associated with lower DFS and OS and poor treatment response. So, we recommend carrying out XRCC3 genotyping before starting treatment to choose the most effective treatment strategy according to XRCC3 polymorphism.

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Genetic Predisposition to Breast and Ovarian Cancers: How Many and Which Genes to Test?

Breast and ovarian cancers are some of the most common tumors in females, and the genetic predisposition is emerging as one of the key risk factors in the development of these two malignancies. BRCA1 and BRCA2 are the best-known genes associated with hereditary breast and ovarian cancer. However, recent advances in molecular techniques, Next-Generation Sequencing in particular, have led to the identification of many new genes involved in the predisposition to breast and/or ovarian cancer, with different penetrance estimates. TP53, PTEN, STK11, and CDH1 have been identified as high penetrance genes for the risk of breast/ovarian cancers. Besides them, PALB2, BRIP1, ATM, CHEK2, BARD1, NBN, NF1, RAD51C, RAD51D and mismatch repair genes have been recognized as moderate and low penetrance genes, along with other genes encoding proteins involved in the same pathways, possibly associated with breast/ovarian cancer risk. In this review, we summarize the past and more recent findings in the field of cancer predisposition genes, with insights into the role of the encoded proteins and the associated genetic disorders. Furthermore, we discuss the possible clinical utility of genetic testing in terms of prevention protocols and therapeutic approaches.

Analysis of the association between the XRCC2 rs3218536 polymorphism and ovarian cancer risk

INTRODUCTION

Results conflict on the association between the XRCC2 rs3218536 polymorphism and ovarian cancer risk, despite wide-ranging investigations. This meta-analysis examines whether the XRCC2 rs3218536 polymorphism is associated with ovarian cancer risk.

MATERIAL AND METHODS

Eligible case-control studies were searched in PubMed. We therefore performed a meta-analysis of 5,802 ovarian cancer cases and 9,390 controls from 7 articles published. The strength of association between XRCC2 rs3218536 polymorphism and ovarian cancer susceptibility was calculated using pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs).

RESULTS

No statistically significant associations between XRCC2 rs3218536 polymorphism and ovarian cancer risk were found in any genetic models. However, a significant relationship with ovarian cancer risk was discovered when the high quality studies were pooled in the meta-analysis (AA vs. GG: OR = 0.59, 95% CI: 0.37-0.94, p = 0.03; GA vs. GG: OR = 0.87, 95% CI: 0.78-0.96, p = 0.009; GA + AA vs. GG: OR = 0.85, 95% CI: 0.77-0.94, p = 0.003; AA vs. GG + GA: OR = 0.60, 95% CI: 0.38-0.95, p = 0.03).

CONCLUSIONS

This meta-analysis shows that the XRCC2 rs3218536 polymorphism was associated with ovarian cancer risk overall for high quality studies. Non-Caucasian groups and high quality studies should be further studied.

Polymorphisms of XRCC3 and XRCC7 and Colorectal Cancer Risk in Khorasan Razavi Province, Iran

Background: Colorectal cancer (CRC) is highly prevalent cancer, which should be genetically studied among different peoples of the world. Objective: The aim of this study was to evaluate the effect of XRCC3T241M, XRCC3 A17893G and, for the first time, XRCC7 I3434T polymorphisms on CRC risk in Khorasan Razavi Province, Iran. Materials and Methods: In this case-control study, 180 patients with CRC and 160 sex- and age-matched healthy controls were studied. Genotypes were determined by RFLP-PCR and ARMS-PCR. Results: The incidence of CRC was observed to be significantly more in a heterozygous XRCC3 C/T genotype than in the CC genotype (OR 2.210, 95% CI 1.073-4.548, p=0.030). In the case of the XRCC7 I3434T polymorphism, CRC risk was significantly (4.3 fold) higher in I/T+T/T variant subjects compared to the I/I genotype (OR 4.394, 95% CI 2.721-7.096, p=0.000). Moreover, the XRCC3 A17893G polymorphism did not correlate with CRC. In addition, there was no significant difference between the distribution of genotypes of the three studied polymorphisms with demographic and clinicopathological features in the CRC patients. Conclusion: Polymorphisms of XRRC3 and XRCC7 genes are involved in CRC and should be considered as a risk factor.

RAD51 and XRCC3 Polymorphisms Are Associated with Increased Risk of Prostate Cancer

Genetic polymorphisms in DNA repair genes may affect DNA repair efficiency and may contribute to the risk of developing cancer. The aim of our study was to investigate single nucleotide polymorphisms (SNPs) in RAD51 (rs2619679, rs2928140, and rs5030789) and XRCC3 (rs1799796) involved in DNA double-strand break repair and their relationship to prostate cancer. The study group included 99 men diagnosed with prostate cancer and 205 cancer-free controls. SNP genotyping was performed using the PCR-RFLP method. A significant association was detected between RAD51 rs5030789 polymorphism and XRCC3 rs1799796 polymorphism and an increased risk of prostate cancer. Our results indicate that RAD51 and XRCC3 polymorphism may contribute to prostate cancer.

Contribution of germline deleterious variants in the RAD51 paralogs to breast and ovarian cancers

RAD51 paralogs (RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3) have recently been involved in breast and ovarian cancer predisposition: RAD51B, RAD51C, and RAD51D in ovarian cancer, RAD51B and XRCC2 in breast cancer. The aim of this study was to estimate the contribution of deleterious variants in the five RAD51 paralogs to breast and ovarian cancers. The five RAD51 paralog genes were analyzed by next-generation sequencing technologies in germline DNA from 2649 consecutive patients diagnosed with breast and/or ovarian cancer. Twenty-one different deleterious variants were identified in the RAD51 paralogs in 30 patients: RAD51B (n = 4), RAD51C (n = 12), RAD51D (n = 7), XRCC2 (n = 2), and XRCC3 (n = 5). The overall deleterious variant rate was 1.13% (95% confidence interval (CI): 0.72-1.55%) (30/2649), including 15 variants in breast cancer only cases (15/2063; 0.73% (95% CI: 0.34-1.11%)) and 15 variants in cases with at least one ovarian cancer (15/570; 2.63% (95% CI: 1.24-4.02%)). This study is the first evaluation of the five RAD51 paralogs in breast and ovarian cancer predisposition and it demonstrates that deleterious variants can be present in breast cancer only cases. Moreover, this is the first time that XRCC3 deleterious variants have been identified in breast and ovarian cancer cases.

Associations between XRCC2 rs3218536 and ERCC2 rs13181 polymorphisms and ovarian cancer

Recent studies explored XRCC2 rs3218536 and ERCC2 rs13181 polymorphisms and ovarian cancer (OC) risk. However, the association between these two single nucleotide polymorphisms and OC risk remains conflicting. Thus, we conducted a comprehensive systematic review and meta-analysis to investigate the association. We searched the databases of PubMed, and Embase. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by using fixed-effect or random-effect models. 15 case-control studies published in 11 papers including 4,757 cases and 8,431 controls were included in this meta-analysis. No associations were obtained between XRCC2 rs3218536 and ERCC2 rs13181 polymorphisms and OC risk. Stratification analyses of Hardy–Weinberg equilibrium status indicated that rs3218536 polymorphism was associated with the decreased risk of OC when in analysis of combined HWE positive studies. In conclusion, this meta-analysis indicates that XRCC2 rs3218536 and ERCC2 rs13181 polymorphisms may not be associated with the risk of OC.

Association between single nucleotide polymorphisms (SNPs) of XRCC2 and XRCC3 homologous recombination repair genes and ovarian cancer in Polish women

The variability, perceived in DNA repair genes, may be of clinical importance for evaluation of the risk of occurrence of a given type of cancer, its prophylactics and therapy. The aim of the present work was to evaluate associations between the risk of ovarian cancer and polymorphisms in the genes, encoding for two key proteins of homologous recombination: XRCC2 Arg188His (c. 563 G>A; rs3218536) and XRCC3 Thr241Met (c. 722 C>T; rs861539). The study consisted of 700 patients with ovarian cancer and 700 healthy subjects. Analysis of the gene polymorphisms was performed using PCR-RFLP (restriction length fragment polymorphism). We found a statistically significant increase of the 188His allele frequency (OR=4.01; 95% CI=3.40-4.72; p<.0001) of XRCC2 in ovarian cancer compared to healthy controls. There were no differences in the genotype and allele distributions and odds ratios of the XRCC3 Thr241Met polymorphism between patient and control groups. Association of these genetic polymorphisms with histological grading showed increased XRCC2 188Arg/His (OR=33.0; 95% CI=14.51-75.05; p<.0001) and 188His/His genotypes (OR=9.37; 95% CI=4.79-18.32; p<.0001) and XRCC3 241Thr/Met (OR=24.28; 95% CI=12.38-47.61; p<.0001) and 241Met/Met genotype frequencies (OR=17.00; 95% CI=8.42-34.28; p<.0001) in grading 1 (G1) as well as 188His (OR=2.78; 95% CI=2.11-3.69; p<.0001) and 241Met allele overrepresentation (OR=2.59; 95% CI=2.08-3.22; p<.0001) in G1 ovarian patients. Finally, with clinical FIGO staging under evaluation, an increase in XRCC2 188His/His homozygote and 188Arg/His heterozygote frequencies in staging I (SI) and XRCC3 Thr/Met heterozygote frequencies in SI was observed. The obtained results indicate that XRCC2 Arg188His and XRCC3 Thr241Met polymorphisms may be positively associated with the incidence of ovarian carcinoma in the population of Polish women.

Polymorphisms in DNA Repair Gene XRCC3 and Susceptibility to Breast Cancer in Saudi Females

We investigated three common polymorphisms (SNPs) in the XRCC3 gene (rs861539, rs1799794, and rs1799796) in 143 Saudi females suffering from breast cancer (median age = 51.4 years) and 145 age matched normal healthy controls. DNA was extracted from whole blood and genotyping was conducted using PCR-RFLP. rs1799794 showed significant association, where AA and AA+AG occurred at a significantly higher frequency in the cancer patients compared to the control group (OR: 28.1; 95% CI: 3.76-21.12; χ (2): 22.82; p < 0.0001). The G allele was protective and presented with a dominant model. The genotype and allele frequencies of rs861539 C>T and rs1799796 A>G did not show a significant difference when the results in the patients and controls were compared. However, the frequency of rs1799796 differed significantly in patients with different age of diagnosis, tumor grade, and ER and HER2 status. The wild type A allele occurred at a higher frequency in the ER- and HER2- group. Our results among Saudis suggest that some variations in XRCC3 may contribute to breast cancer susceptibility. In conclusion, the results obtained during this study suggest that rs1799794 in XRCC3 shows strong association with breast cancer development in Saudi females.

Analysis of XRCC2 and XRCC3 gene polymorphisms in pancreatic cancer

The double-strand break DNA repair pathway, including XRCC2 and XRCC3 genes, is implicated in maintaining genomic stability and therefore could affect the pancreatic cancer risk. The aim of the present study was to evaluate the clinical significance of the XRCC2 and XRCC3 gene polymorphisms in patients with pancreatic cancer. The present study included 203 patients: 101 with pancreatic cancer and 102 healthy controls. The Arg188His XRCC2 and the Thr241Met XRCC3 gene polymorphisms have been studied in DNA isolated from blood samples. The associations of the analysed genotypes and clinical data at diagnosis have been evaluated. The frequencies of the genotypes of the Arg188His XRCC2 and Thr241Met XRCC3 polymorphisms did not differ significantly between patients and controls. The study did not identify a correlation between the XRCC2 and XRCC3 genes polymorphisms and tumor size or localisation. Analysed polymorphisms were also not associated with the gender and age of the patient, or the presence of regional or distant metastases. In conclusion, the present study did not suggest an association between the Arg188His XRCC2 and the Thr241Met XRCC3 polymorphisms and the clinical data of patients with pancreatic cancer.

Association between the rs11614913 variant of miRNA-196a-2 and the risk of epithelial ovarian cancer

Polymorphisms in microRNA (miR) genes and their target sites are a distinct classification of variation in the human genome, which are rapidly being identified and investigated in human cancer. A polymorphism in the miR-196a-2 locus has demonstrated significant associations with various types of cancer, including lung, breast, esophageal and gastric tumors. However, miR-196a-2 has not been fully explored in ovarian cancer, which shares similar biological characteristics with other types of cancer. Therefore, the present study aimed to elucidate the association between a single nucleotide polymorphism (SNP) in the mature sequence of miR-196a-2 (rs11614913, T/C) and the clinical features of 479 Chinese patients with epithelial ovarian cancer (EOC). In addition, the biological significance of this polymorphism was investigated in the OVCAR3 ovarian cancer cell line. Risk association was evaluated in 479 cases of EOC patients and 431 controls. SNPs were analyzed by using polymerase chain reaction based restriction fragment length polymorphism assay. miR-196a expression was evaluated with reverse transcription polymerase chain reaction. The influence of miR-196a-2 rs11614913 T/C on EOC cell migration and invasion ability was further investigated in vitro. The results revealed significant differences in the homozygous CC genotype distribution in patients with EOC (n=479), compared with that of the control subjects (n=431; P=0.026). Analysis of the association between genotype and the risk of EOC revealed that individuals who carried the homozygous CC genotype were 1.34-fold more susceptible to EOC, compared with those carrying the wild-type TT and heterozygous CT genotypes [odds ratio, 1.34; 95% confidence interval, 1.04-2.17; P=0.023]. In addition, the role of this polymorphism in the production of mature miR-196a was investigated. Significantly enhanced production of mature miR-196a was revealed in the C-allelic compared with that of the T-allelic miR-196a-2 precursor (P<0.05). Further examination indicated that miR-196a significantly promoted cell migration and invasion ability in the human OVCAR3 ovarian cell line (P<0.05). In conclusion, the results indicated that the miR-196a-2 rs11614913 CC genotype may increase the risks of ovarian cancer by affecting the expression of mature miR-196a and enhancing cell migration/invasion. The current results provided evidence that the T>C polymorphism in the miR-196a-2 precursor may influence tumorigenesis and metastasis in EOC, and suggested that the functional SNP rs11614913 in the promoter region of pri-miR-196a-2 may be a potential indicator of EOC susceptibility in the population analyzed.