Association between RAD51 gene polymorphism (-135G/C) and susceptibility of myelodysplastic syndrome and acute leukemia: evidence based on a meta-analysis

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.

The association of three DNA repair genes polymorphisms on the frequency of chromosomal alterations detected by fluorescence in situ hybridization

PURPOSE

Gas station workers (GSWs) are exposed to carcinogenic agents. The aim was to study the association of high somatic chromosome alterations (CAs) rates in the blood of GSWs and the polymorphisms of three genes playing a role in DNA double-strand break repair.

METHODS

This is a cross-sectional study with 114 GSWs and 115 age-matched controls. Cytogenetic analyses, blood exams, medical interviews and genotypes for RAD51/G135C (rs1801320), ATM/P1054R (rs1800057) and CHEK2/T470C (rs17879961) genes were performed.

RESULTS

The CA rate in GSWs was 9.8 CAs/1000 metaphases, and 19.1% of the workers had > 10 CAs per 1000 metaphases (group two). GSWs had decreased levels of monocytes (P = 0.024) in their blood exams. The number of variant alleles of the RAD51/G135C polymorphism was higher in GSWs (P = 0.011) compared to the controls, and were associated with enhanced number of CAs per worker (P = 0.008). No allele variant was found for CHEK2/T470C in this study.

CONCLUSION

The RAD51/G135C polymorphism appears to be related to genome instability in gas station workers. Increasing the knowledge of DNA repair gene variations involved in maintaining genomic stability in GSWs may be crucial for future cancer prevention.

MicroRNA-107 promotes apoptosis of acute myelocytic leukemia cells by targeting RAD51

INTRODUCTION

This study aimed to investigate the role of microRNA (miRNA) that affects acute myelocytic leukemia (AML) and its potential molecular mechanism by constructing a miRNA-mRNA interaction network using bioinformatics methods.

MATERIAL AND METHODS

MicroRNA expression data of AML were retrieved from Gene Expression Omnibus (GEO) and analyzed by microarray analysis. Expression levels of miR-107 and RAD51 mRNA were detected by quantitative real time polymerase chain reaction (qRT-PCR). Protein expression of RAD51, pro-apoptotic protein Bax, apoptosis related protein CytC and anti-apoptotic protein Bcl-2 were determined by Western blot. The rate of cell apoptosis was detected by Annexin-V/PI. The predicted targeting relationship between miR-107 and the 3'UTR of RAD51 was first predicted by the online application TargetScan and then verified by dual-luciferase assay.

RESULTS

Acute myelocytic leukemia-associated genes (n = 197) and miRNAs (n = 1701) were retrieved from the database, the interaction network of miRNA-mRNA was constructed and the core position was occupied by RAD51. miR-107 exhibited a regulatory effect on RAD51 in which the mRNA and protein expression of RAD51 were both significantly inhibited by miR-107 mimics in vitro. Additionally, down-regulated expression of miR107 as well as up-regulated expression of RAD51 were detected not only in the plasma of AML patients compared to healthy volunteers, but also in AML cell lines compared to the normal bone marrow stromal cell line. Further study found that increased expression of miR-107 and the consequent down-regulation of RAD51 could aggravate the apoptosis of AML cells in vitro.

CONCLUSIONS

Our present results showed that the crucial role of RAD51 and miR-107 in the apoptosis of AML cells, i.e., miR-107 promotes the apoptosis of AML cells through down-regulating the expression of RAD51.

Applying a Weight-of-Evidence Approach to Evaluate Relevance of Molecular Landscapes in the Exposure-Disease Paradigm

Information on polymorphisms, mutations, and epigenetic events has become increasingly important in our understanding of molecular mechanisms associated with exposures-disease outcomes. Molecular landscapes can be developed to illustrate the molecular characteristics for environmental carcinogens as well as associated disease outcomes, although comparison of these molecular landscapes can often be difficult to navigate. We developed a method to organize these molecular data that uses a weight-of-evidence approach to rank overlapping molecular events by relative importance for susceptibility to an exposure-disease paradigm. To illustrate the usefulness of this approach, we discuss the example of benzene as an environmental carcinogen and myelodysplastic syndrome (MDS) as a causative disease endpoint. Using this weight-of-evidence method, we found overlapping polymorphisms in the genes for the metabolic enzymes GST and NQO1, both of which may infer risk of benzene-induced MDS. Polymorphisms in the tumor suppressor gene, TP53, and the inflammatory cytokine gene, TNF-α, were also noted, albeit inferring opposing outcomes. The alleles identified in the DNA repair gene RAD51 indicated an increased risk for MDS in MDS patients and low blood cell counts in benzene-exposed workers. We propose the weight-of-evidence approach as a tool to assist in organizing the sea of emerging molecular data in exposure-disease paradigms.

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.

Association of MDR1 G2677T polymorphism and leukemia risk: evidence from a meta-analysis

In the light of the relationship between the MDR1 G2677T polymorphism and the risk of leukemia remains inclusive or controversial. For better understanding of the effect of MDR1 G2677T polymorphism on leukemia risk, we performed a meta-analysis. Eligible studies were identified through a search of electronic databases such as PubMed, Excerpta Medica Database (Embase), Cochrane Library, and Chinese Biomedical Literature Database (CBM). The association between the MDR1 G2677T polymorphism and leukemia risk was conducted by odds ratios (ORs) and 95% confidence intervals (95% CI). A total of seven publications including eight studies with 1,229 cases and 1,097 controls were included in the meta-analysis. There was no association between MDR1 G2677T polymorphism and leukemia risk in all of five models in overall populations (T vs. G: OR = 1.00, 95% CI = 0.88-1.12, P = 0.914; TT vs. GG: OR = 0.97, 95% CI = 0.75-1.26, P = 0.812; TG vs. GG: OR = 1.00, 95% CI = 0.92-1.08, P = 0.939; TT vs.

TG/GG

OR = 0.98, 95% CI = 0.67-1.43, P = 0.906; TT/TG vs. GG: OR = 1.00, 95% CI = 0.95-1.06, P = 0.994). However, the significant association was found in others (Table 2) under the homozygote model (TT vs. GG: OR = 0.68, 95% CI = 0.48-0.94, P = 0.020) and recessive model (TT vs.

TG/GG

OR = 0.63, 95% CI = 0.43-0.92, P = 0.016). In the subgroup analysis, according to the type of leukemia, significant association was found between MDR1 G2677T polymorphism and myeloid leukemia but not lymphoblastic leukemia (TT vs. GG: OR = 0.66, 95% CI = 0.46-0.95, P = 0.026; TT vs.

TG/GG

OR = 0.56, 95% CI = 0.38-0.84, P = 0.005). The results suggested that there was no association between MDR1 G2677T polymorphism and leukemia risk in overall populations, but significant association was found in others populations (Asians and Africans), and myeloid leukemia indicated that G2677T polymorphism might be a protective factor in the susceptibility of myeloid leukemia and in Asians and Africans.

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.