RAD51 G135C polymorphism is associated with breast cancer susceptibility: a meta-analysis involving 22,399 subjects

Homologous recombination DNA repair gene RAD51, XRCC2 & XRCC3 polymorphisms and breast cancer risk in South Indian women

BACKGROUND

Homologous recombination repair (HRR) accurately repairs the DNA double-strand breaks (DSBs) and is crucial for genome stability. Genetic polymorphisms in crucial HRR pathway genes might affect genome stability and promote tumorigenesis. Up to our knowledge, the present study is the first to investigate the impact of HRR gene polymorphisms on BC development in South Indian women. The present population-based case-control study investigated the association of polymorphisms in three key HRR genes (XRCC2-Arg188His, XRCC3-Thr241Met and RAD51-G135C) with BC risk.

MATERIALS AND METHODS

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used for genotyping the HRR variants in 491 BC cases and 493 healthy women.

RESULTS

We observed that the XRCC3 Met allele was significantly associated with BC risk [OR:1.27 (95% CI: 1.02-1.60); p = 0.035]. In addition, the homozygous mutant (C/C) genotype of RAD51 G135C variant conferred 2.19 fold elevated risk of BC [OR: 2.19 (95% CI: 1.06-4.54); p = 0.034]. Stratified analysis of HRR variants and BC clinicopathological features revealed that the XRCC3-Thr241Met and RAD51-G135C variants are associated with BC progression. Combined SNP analysis revealed that the individuals with RAD51-C/C, XRCC2-Arg/Arg, and XRCC3-Thr/Thr genotype combination have three-fold increased BC risk.

CONCLUSION

The present study imparts additional evidence that genetic variants in crucial HRR pathway genes might play a pivotal role in modulating BC risk in South Indian women.

Association of RAD51 and XRCC2 Gene Polymorphisms with Cervical Cancer Risk in the Bangladeshi Women

Objective:

Alterations in common DNA repair genes (RAD51 and XRCC2) may lead to cervical cancer (CC) development. In the present study, we analyzed the association between RAD51 rs1801320 and XRCC2 rs3218536 polymorphisms and CC.

Methods:

Variants were selected based on their associations with some cancers in several ethnicities and the risk allele frequency (>0.05) in different populations. The variants were detected using the PCR-RFLP method. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were determined by logistic regression models.

Result:

Significantly increased risk (p<0.05) were detected for both SNPs with CC (rs1801320- GC vs. GG: aOR=2.21, 95% CI=1.43-3.42; CC vs. GG: aOR=4.48, 95% CI=1.76-11.42; dominant model: aOR=2.49, 95% CI=1.65-3.76; recessive model: aOR=3.52, 95% CI=1.40-8.88; allele model: OR=2.30, 95% CI=1.63-3.26, and rs3218536- GA vs. GG: aOR=2.77, 95% CI=1.85-4.17; AA vs. GG: aOR=5.86, 95% CI=2.08-16.50; dominant model: aOR=2.97, 95% CI=1.99-4.42; recessive model: aOR=3.56, 95% CI=1.30-9.73; and allele model: aOR=2.21, 95% CI=1.62-3.00). Besides, older patients (>60 years) with rs1801320 showed significantly reduced risk (OR=0.53, 95% CI=0.29-0.96, p=0.04) but with rs3218536 depicted significantly increased risk (aOR=2.44, 95% CI=1.20-4.96, p=0.01) for CC.

Conclusion:

This study indicates an association of rs1801320 and rs3218536 polymorphisms with CC and confirms that patients older than 60 years are more likely to develop CC for rs3218536 polymorphism.

Polymorphic Variants in 5'-UTR Regions of the RAD51 Gene are Associated With RAD51 Expression and Triple-Negative Breast Cancer (TNBC): A Case-Control Study

Breast cancer is a heterogeneous disease at morphologic and molecular levels, which is considered the most commonly occurring cancer in women. RAD51, a DNA-repairing protein, involves homologous recombination and has a vital role in genome stability. Polymorphism of the RAD51 gene, and its overexpression, has been proposed to be associated with the development of breast cancer. Overexpression of RAD51 in many types of human cancer including metastatic breast cancer may signify its potential use as a biomarker. Considering the numerous reports on the role of the 5'-UTR-RAD51 polymorphism in breast cancer, this study aimed to investigate the utility of RAD51 gene expression and its variants G135C and G172T as a possible foretelling factor of breast cancer development. DNA sequencing and immunohistochemistry of RAD51 were conducted on 103 samples from patients diagnosed with sporadic breast cancer and 80 samples from a control group. The results demonstrated that the RAD51 variants, G135C and G172T, were significantly presented in the breast cancer tissue compared with the control group. RAD51 expression was mainly shown in the cytoplasm of malignant cells (56% of cases) and significantly correlated with p53 and G135C, C135C variants. Moreover, the occurrence of the G172T variant was significantly associated with the expression of estrogen receptor. Interestingly, 21/26 (81%) of the triple-negative breast cancer showed G135C and C135C genotypes that were significantly associated with the expression of RAD51 (73%). In conclusion, the G135C and C135C variants together with the cytoplasmic expression of RAD51 may have clinical potential as a prognostic predictor for breast cancer development and aggressiveness.

Rad51 paralogs and the risk of unselected breast cancer: A case-control study

A case-control study was conducted in which we evaluated the association between genetic variability of DNA repair proteins belonging to the Rad51 family and breast cancer (BrC) risk. In the study, 132 female BrC cases and 189 healthy control females were genotyped for a total of 14 common single nucleotide polymorphisms (SNPs) within Rad51 and Xrcc3. Moreover, our previously reported Rad51C genetic data were involved to explore the nonlinear interactions among SNPs within the three genes and effect of such interactions on BrC risk. The rare rs5030789 genotype (-4601AA) in Rad51 was found to significantly decrease the BrC risk (OR = 0.5, 95% CI: 0.3-1.0, p<0.05). An interaction between this SNP, rs2619679 and rs2928140 (both in Rad51), was found to result in a two three-locus genotypes -4719AA/-4601AA/2972CG and -4719AT/-4601GA/2972CC, both of which were found to increase the risk of BrC (OR = 8.4, 95% CI: 1.8-38.6, p<0.0001), instead. Furthermore, rare Rad51 rs1801320 (135CC) and heterozygous Xrcc3 rs3212057 (10343GA) genotypes were found to respectively increase (OR = 10.6, 95% CI: 1.9-198, p<0.02) and decrease (OR = 0.0, 95% CI: 0.0-NA, p<0.05) the risk of BrC. Associations between these SNPs and BrC risk were further supported by outcomes of employed machine learning analyses. In Xrcc3, the 4541A/9685A haplotype was found to be significantly associated with reduced BrC risk (OR = 0.5; 95% CI: 0.3-0.9; p<0.05). Concluding, our study indicates a complex role of SNPs within Rad51 (especially rs5030789) and Xrcc3 in BrC, although their significance with respect to the disease needs to be further clarified.

Homozygous T172T and Heterozygous G135C Variants of Homologous Recombination Repairing Protein RAD51 are Related to Sporadic Breast Cancer Susceptibility

Breast cancer (BC) is the most common cancer and the second leading cause of death among women worldwide. Only 10% of BC cases have been related to genetic predisposition. Rad51, a homologous recombination (HR) protein plays an important role in HR in meiosis and repairing DNA double-strand breaks. Expression of RAD51 may be a predictive biomarker in certain types of cancers. The exact mechanisms involved in the regulation of RAD51 expression are not fully understood, but certain transcription factors have been suggested to be the tuning mechanism of its expression. In this study, we propose that polymorphisms in the 5'-UTR promoter region of the RAD51 gene are prognostic factors for BC development. Direct sequencing of 106 samples from sporadic BC patients and 54 samples from a control group was performed. FFPE samples were the choice of sample collection, which might be a limitation of our study. Homologous variant T172T alone was found to be significantly associated with BC risk (OR 3.717, 95% CI 2.283-6.052, p < 0.0001). On the other hand, heterozygous G135C did not show any significant relationship with risk of sporadic BC (OR 1.598, 95% CI 0.5638-4.528, p > 0.05). Moreover, both variants; homozygous T172T and heterozygous G135C together; showed a significant relationship with sporadic BC susceptibility.

Polymorphisms of homologous recombination RAD51, RAD51B, XRCC2, and XRCC3 genes and the risk of prostate cancer

Genetic polymorphisms in DNA repair genes may induce individual variations in DNA repair capacity, which may in turn contribute to the risk of cancer developing. Homologous recombination repair (HRR) plays a critical role in maintaining chromosomal integrity and protecting against carcinogenic factors. The aim of the present study was to evaluate the relationship between prostate cancer risk and the presence of single nucleotide polymorphisms (SNPs) in the genes involved in HRR, that is, RAD51 (rs1801320 and rs1801321), RAD51B (rs10483813 and rs3784099), XRCC2 (rs3218536), and XRCC3 (rs861539). Polymorphisms were analyzed by PCR-RFLP and Real-Time PCR in 101 patients with prostate adenocarcinoma and 216 age- and sex-matched controls. A significant relationship was detected between the RAD51 gene rs1801320 polymorphism and increased prostate cancer risk. Our results indicate that the RAD51 gene rs1801320 polymorphism may contribute to prostate cancer susceptibility in Poland.

Genetic 135G/C polymorphism of RAD51 gene and risk of cancer: a meta-analysis of 28,956 cases and 28,372 controls

The RAD51 gene is essential for the repair of damaged DNA related to tumor development. Although a number of genetic studies have attempted to link the 135G/C polymorphism of RAD51 gene to the risk of cancer, the results were inconclusive. The present study aimed at investigating the pooled association using the more comprehensive meta-analysis. The PubMed, EBSCO, and BIOSIS databases were searched to identify eligible studies which were published in English before March 2014. Data were extracted using standardized methods. The association was assessed by odds ratio (OR) with 95 % confidence interval (CI). Begg's test was used to measure publication bias. Sensitivity analyses were also performed to assess the stability of the results. A total of 45 eligible studies with 28,956 patients and 28,372 controls were included in this meta-analysis. Overall, significant association was detected between 135G/C polymorphism and increased cancer risk (C allele vs. G allele: OR 1.23, 95 % CI 1.18-1.28; CC vs. GG: OR 2.41, 95 % CI 2.12-2.74; CC vs. CG: OR 3.86, 95 % CI 3.41-4.37; recessive model: OR 3.57, 95 % CI 3.19-4.00). In further stratified analysis, significantly elevated cancer risk was observed among Caucasians but not Asians. Subgroup analysis by different cancers also showed their significant associations in breast cancer, hematologic malignances, ovarian cancer, colorectal cancer and endometrial cancer, but not in head and neck cancer. Our results indicated that the RAD51 135G/C polymorphism was a candidate for susceptibility of cancer. The effect of the variants on the expression levels and the possible functional role of the variants in different cancers should be addressed in further studies.

Mechanisms and regulation of mitotic recombination in Saccharomyces cerevisiae

Homology-dependent exchange of genetic information between DNA molecules has a profound impact on the maintenance of genome integrity by facilitating error-free DNA repair, replication, and chromosome segregation during cell division as well as programmed cell developmental events. This chapter will focus on homologous mitotic recombination in budding yeast Saccharomyces cerevisiae. However, there is an important link between mitotic and meiotic recombination (covered in the forthcoming chapter by Hunter et al. 2015) and many of the functions are evolutionarily conserved. Here we will discuss several models that have been proposed to explain the mechanism of mitotic recombination, the genes and proteins involved in various pathways, the genetic and physical assays used to discover and study these genes, and the roles of many of these proteins inside the cell.

RAD51 135G>C substitution increases breast cancer risk in an ethnic-specific manner: a meta-analysis on 21,236 cases and 19,407 controls

RAD51 is a homolog of bacterial RecA protein, which plays an important role in preserving stability of the genome. RAD51 interacts with BRCA1 and BRCA2 for homologous recombination repair. A functional polymorphism (135G > C) in the RAD51 gene has been a subject of great interest, which is evidenced by at least 28 case-control studies and eight meta-analyses undertaken on this polymorphism till now. We undertook a meta-analysis on RAD51 135G > C data for 21236 cases and 19407 controls pooled from 28 studies on breast cancer in women. Pooled data analysis suggested a significant association of the substitution with breast cancer in the recessive model (GG + GC versus CC) and in the co-dominant models comparing GG versus CC and GC versus CC. Analysis of the results suggested that ‘CC’ genotype is a significant breast cancer risk factor in comparison to ‘GG’ and ‘GC’ genotypes. We also undertook pooled analyses on different ethnic groups and found that ‘CC’ was a strong risk factor in Caucasians, but not in East-Asians and populations of mixed ethnicity. In conclusion, the RAD51 135G > C substitution in the homozygous form (CC) increases the risk of breast cancer in an ethnic-specific manner.

RAD51 135G>C and TP53 Arg72Pro polymorphisms and susceptibility to breast cancer in Serbian women

Breast cancer is a complex disease with both genetic and environmental factors involved in its etiology. An important role of polymorphisms in genes involved in DNA repair has been reported related to breast cancer risk. We conducted a case-control study in order to investigate the association of RAD51 135G>C and TP53 Arg72Pro polymorphisms with breast cancer in Serbian women.48 BRCA negative women with breast cancer and family history of breast/ovarian cancer (hereditary group), 107 women with breast cancer but without family history of the disease (sporadic group) and 114 healthy women without a history of the disease (control group) were included. Restriction fragment length polymorphism was used for genotyping. Genotype and allelic frequencies, the odds ratio (OR) and the 95 % confidence interval (CI) were calculated as an estimate of relative risk. The Hardy-Weinberg equilibrium was tested using χ(2) test. Significance was considered for p < 0.05. RAD51 135G>C showed statistically significant association of CC genotype and increased breast cancer risk (OR 10.28, 95 % CI 1.12-94.5) in hereditary group of patients compared to the control group. Regarding the TP53 Arg72Pro, we showed statistical significance for ProPro + ProArg comparing to ArgArg (OR 2.34, 95 %, CI 1.17-4.70) in hereditary compared to sporadic group. RAD51 135G>C contributes to hereditary breast cancer in Serbian population, with CC genotype as a risk factor. We also found that carriers of Pro allele of TP53 codon 72 is related to hereditary cancer comparing to sporadic one, which indicates it as a potential risk factor for hereditary form of disease.

Haplotype analyses of DNA repair gene polymorphisms and their role in ulcerative colitis

Ulcerative colitis (UC) is a major clinical form of inflammatory bowel disease. UC is characterized by mucosal inflammation limited to the colon, always involving the rectum and a variable extent of the more proximal colon in a continuous manner. Genetic variations in DNA repair genes may influence the extent of repair functions, DNA damage, and thus the manifestations of UC. This study thus evaluated the role of polymorphisms of the genes involved in DNA repair mechanisms. A total of 171 patients and 213 controls were included. Genotyping was carried out by ARMS PCR and PCR-RFLP analyses for RAD51, XRCC3 and hMSH2 gene polymorphisms. Allelic and genotypic frequencies were computed in both control & patient groups and data was analyzed using appropriate statistical tests. The frequency of 'A' allele of hMSH2 in the UC group caused statistically significant increased risk for UC compared to controls (OR 1.64, 95% CI 1.16-2.31, p = 0.004). Similarly, the CT genotype of XRCC3 gene was predominant in the UC group and increased the risk for UC by 1.75 fold compared to controls (OR 1.75, 95% CI 1.15-2.67, p = 0.03), further confirming the risk of 'T' allele in UC. The GC genotype frequency of RAD51 gene was significantly increased (p = 0.02) in the UC group (50.3%) compared to controls (38%). The GC genotype significantly increased the risk for UC compared to GG genotype by 1.73 fold (OR 1.73, 95% CI 1.14-2.62, p = 0.02) confirming the strong association of 'C' allele with UC. Among the controls, the SNP loci combination of hMSH2:XRCC3 were in perfect linkage. The GTC and ACC haplotypes were found to be predominant in UC than controls with a 2.28 and 2.93 fold significant increase risk of UC.

Relationship between Rad51 G135C and G172T variants and the susceptibility to cancer: a meta-analysis involving 54 case-control studies

Background

The associations between Rad51 gene polymorphisms (G135C and G172T) and risk of cancer have been investigated, but the results were inconclusive. To get a comprehensive evaluation of the association above, we performed a meta-analysis of published studies.

Methods

A computerized search of PubMed, Embase and Web of Knowledge databases for all relevant studies was performed and the data were analyzed in a meta-analysis. The overall odds ratio (OR) with the 95% confidence interval (95% CI) was calculated to assess the strength of the association between Rad51 polymorphisms and cancer risk. Data were analyzed using fixed- or random-effects model when appropriate. Sensitivity analysis and publication bias test were also estimated.

Results

Overall, a total of 54 case-control studies were included in the current meta-analysis, among which 42 studies with 19,142 cases and 20,363 controls for RAD51 G135C polymorphism and 12 studies with 6,646 cases and 6,783 controls for G172T polymorphism. For G135C polymorphism, the pooled results indicated that significantly increased risk was found in overall cancers (homozygote model: OR = 1.776, 95% CI = 1.288–2.449; allelic genetic model: OR = 1.169, 95% CI = 1.016–1.345; recessive model: OR = 1.946, 95% CI = 1.336–2.835), especially in breast cancer (homozygote model: OR = 1.498, 95% CI = 1.026–2.189; recessive model: OR = 1.732, 95% CI  =  1.170–2.562). For G172T polymorphism, a decreased cancer risk was observed in head and neck cancer (homozygote model: OR  =  0.621, 95% CI  =  0.460–0.837; allelic genetic model: OR  =  0.824, 95% CI  =  0.716–0.948; recessive model: OR  =  0.639, 95% CI = 0.488–0.837).

Conclusions

Our results suggested that the Rad51 G135C polymorphism is a candidate for susceptibility to overall cancers, especially to breast cancer, and that the Rad51 G172T might play a protective role in the development of head and neck cancer.

Association between the RAD51 135 G>C polymorphism and risk of cancer: a meta-analysis of 19,068 cases and 22,630 controls

BACKGROUND

RAD51 135G>C can modify promoter activity and the penetrance of BRCA1/2 mutations, which plays vital roles in the etiology of various cancer. To date, previous published data on the association between RAD51 135G>C polymorphism and cancer risk remained controversial. Recent meta-analysis only analyzed RAD51 135G>C polymorphism with breast cancer risk, but the results were also inconsistent.

METHODS

A meta-analysis based on 39 case-control studies was performed to investigate the association between cancer susceptibility and RAD51 135G>C. Odds ratios (OR) with 95% confidence intervals (CIs) were used to assess the association in different inheritance models. Heterogeneity among studies was tested and sensitivity analysis was applied.

RESULTS

Overall, no significant association was found between RAD51 135G>C polymorphism and cancer susceptibility in any genetic model. In further stratified analysis, significantly elevated breast cancer risk was observed in BRCA2 mutation carriers (recessive model: OR = 4.88, 95% CI = 1.10-21.67; additive model: OR = 4.92, 95% CI = 1.11-21.83).

CONCLUSIONS

This meta-analysis suggests that RAD51 variant 135C homozygote is associated with elevated breast cancer risk among BRCA2 mutation carriers. Moreover, our work also points out the importance of new studies for RAD51 135G>C association in acute myeloid leukemia, especially in Caucasians, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the RAD51 135G>C polymorphism in cancer development.

Two nonsynonymous polymorphisms (F31I and V57I) of the STK15 gene and breast cancer risk: a meta-analysis based on 5966 cases and 7609 controls

OBJECTIVES

This meta-analysis examined the relationship between two nonsynonymous polymorphisms (F31I and V57I) of the aurora kinase A (STK15) gene and breast cancer risk.

METHODS

A systematic search of the PubMed® and EMBASE™ databases was undertaken to identify case-control studies that investigated the relationship between STK15 gene polymorphisms and breast cancer risk.

RESULTS

This meta-analysis included seven case-control studies (5966 breast cancer cases; 7609 controls). Combined results, based on all seven studies, showed that breast cancer cases had a significantly higher frequency of the 31 Ile/Ile genotype. In a subgroup analysis by race, breast cancer cases had a significantly higher frequency of the 31 Ile/Ile genotype in Asians and Caucasians. Combined results, based on four studies, suggested that the STK15 V57I gene polymorphism was unlikely to be associated with breast cancer risk in either Asians or Caucasians.

CONCLUSIONS

The present meta-analysis suggests that the STK15 F31I polymorphism is a strong predisposing risk factor for breast cancer, but no significant association existed between the STK15 V57I polymorphism and the risk of breast cancer.

RAD51 and breast cancer susceptibility: no evidence for rare variant association in the Breast Cancer Family Registry study

Background

Although inherited breast cancer has been associated with germline mutations in genes that are functionally involved in the DNA homologous recombination repair (HRR) pathway, including BRCA1, BRCA2, TP53, ATM, BRIP1, CHEK2 and PALB2, about 70% of breast cancer heritability remains unexplained. Because of their critical functions in maintaining genome integrity and already well-established associations with breast cancer susceptibility, it is likely that additional genes involved in the HRR pathway harbor sequence variants associated with increased risk of breast cancer. RAD51 plays a central biological function in DNA repair and despite the fact that rare, likely dysfunctional variants in three of its five paralogs, RAD51C, RAD51D, and XRCC2, have been associated with breast and/or ovarian cancer risk, no population-based case-control mutation screening data are available for the RAD51 gene. We thus postulated that RAD51 could harbor rare germline mutations that confer increased risk of breast cancer.

Methodology/Principal Findings

We screened the coding exons and proximal splice junction regions of the gene for germline sequence variation in 1,330 early-onset breast cancer cases and 1,123 controls from the Breast Cancer Family Registry, using the same population-based sampling and analytical strategy that we developed for assessment of rare sequence variants in ATM and CHEK2. In total, 12 distinct very rare or private variants were characterized in RAD51, with 10 cases (0.75%) and 9 controls (0.80%) carrying such a variant. Variants were either likely neutral missense substitutions (3), silent substitutions (4) or non-coding substitutions (5) that were predicted to have little effect on efficiency of the splicing machinery.

Conclusion

Altogether, our data suggest that RAD51 tolerates so little dysfunctional sequence variation that rare variants in the gene contribute little, if anything, to breast cancer susceptibility.

Mutation analysis of RAD51L1 (RAD51B/REC2) in multiple-case, non-BRCA1/2 breast cancer families

Although a significant proportion of familial aggregation of breast cancer remains unexplained, many of the currently known breast cancer susceptibility genes, including BRCA1, BRCA2 and TP53, play a role in maintaining genome integrity by engaging in DNA repair. RAD51L1 is one of the five RAD51 paralogs involved in homologous recombination (HR) repair of DNA double-strand breaks (DSBs); it also interacts directly with p53. Deleterious mutations have been found in one RAD51 paralog, RAD51C (RAD51L2), in non-BRCA1/2 breast and ovarian cancer families, which suggests that all five paralogs are strong candidate breast cancer susceptibility genes. A genome-wide association study (GWAS) has already identified a single nucleotide polymorphism (SNP) deep within intron 10 of RAD51L1 as a risk locus for breast cancer. Based on its biological functions and association with RAD51C, there is reason to suggest that RAD51L1 (RAD51B/REC2) may also contain high risk mutations in the gene that give rise to multiple-case breast cancer families. In order to investigate this hypothesis, we have used high resolution melt (HRM) analysis to screen RAD51L1 for germline mutations in 188 non-BRCA1/2 multiple-case breast cancer families and 190 controls. We identified a total of seven variants: one synonymous, three intronic, and three previously identified SNPs, but no truncating or nonsense changes. Therefore, our results suggest that RAD51L1 is unlikely to represent a high-penetrance breast cancer susceptibility gene.