A single-nucleotide polymorphism in the RAD51 gene modifies breast cancer risk in BRCA2 carriers, but not in BRCA1 carriers or noncarriers

TGFBR1*6A as a modifier of breast cancer risk and progression: advances and future prospects

There is growing evidence that germline mutations in certain genes influence cancer susceptibility, tumor evolution, as well as clinical outcomes. Identification of a disease-causing genetic variant enables testing and diagnosis of at-risk individuals. For breast cancer, several genes such as BRCA1, BRCA2, PALB2, ATM, and CHEK2 act as high- to moderate-penetrance cancer susceptibility genes. Genotyping of these genes informs genetic risk assessment and counseling, as well as treatment and management decisions in the case of high-penetrance genes. TGFBR1*6A (rs11466445) is a common variant of the TGF-β receptor type I (TGFBR1) that has a global minor allelic frequency (MAF) of 0.051 according to the 1000 Genomes Project Consortium. It is emerging as a high frequency, low penetrance tumor susceptibility allele associated with increased cancer risk among several cancer types. The TGFBR1*6A allele has been associated with increased breast cancer risk in women, OR 1.15 (95% CI 1.01–1.31). Functionally, TGFBR1*6A promotes breast cancer cell proliferation, migration, and invasion through the regulation of the ERK pathway and Rho-GTP activation. This review discusses current findings on the genetic, functional, and mechanistic associations between TGFBR1*6A and breast cancer risk and proposes future directions as it relates to genetic association studies and mechanisms of action for tumor growth, metastasis, and immune suppression.

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 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.

Use of Electrocatalysis for Differentiating DNA Polymorphisms and Enhancing the Sensitivity of Electrochemical Nucleic Acid-Based Sensors with Covalent Redox Tags-Part II

Single-nucleotide polymorphisms (SNPs), insertion/deletion (indel) polymorphisms, and DNA methylation are the most frequent types of genetic variations. As such, DNA polymorphisms play significant roles in genetic mapping and diagnostics. Thus, analytical methods enabling DNA polymorphism detection will provide an invaluable means for early disease diagnosis. However, no single electrochemical nucleic acid-based sensor has achieved the detection of the three major polymorphisms (SNPs, indel polymorphisms, and DNA methylation) with sufficient specificity and sensitivity. In response, we explore the utilization of a catalytic reaction between methylene blue (MB) covalently linked to surface-bound nucleic acid and freely diffusing ferricyanide (Fe(CN)₆^3-) to improve specificity and sensitivity of DNA polymorphism detection. We find that the dynamics of the nucleic acid tether is an additional rate-limiting factor for the electrocatalytic reaction, in addition to the more traditional kinetic and excess factors. Our proof-of-concept experiments demonstrate that the use of electrocatalysis enables differentiation of the three polymorphisms when target sequences are present at 10 nM. We hypothesize that this ability is a result of the distinct dynamics of the DNA probe with each respective polymorphism. In addition to the specificity the sensor displays, the sensor achieves a 20 pM limit of detection. We believe that the electrocatalysis between nucleic acid-tethered MB and Fe(CN)₆^3- is highly promising for electrochemical nucleic acid-based sensors to achieve better specificity and sensitivity.

Impact of intraoperative radiotherapy on the perioperative period of patients after breast-conserving surgery

BACKGROUND

To investigate the effect of intraoperative radiotherapy (IORT) in the perioperative period of patients after breast-conserving surgery (BCS).

METHODS

The clinical data of 100 patients with early breast cancer undergoing breast-conserving surgery (BCS) followed by treatment with IORT using the Intrabeam system (Carl Zeiss Meditec, Oberkochen, Germany) (BCS + IORT group, n=100) between June 2016 and December 2019 were analyzed and compared with the data of 60 matched patients who only underwent breast-conserving therapy over the same period (BCS group, n=60). The surgical settings and postoperative acute complications between the groups were assessed.

RESULTS

There was no significant statistical difference between the groups in terms of age, tumor size, grading, lymph node status, hormone receptor status, and human epidermal growth factor receptor 2 (HER-2) status (P>0.05). The BCS + IORT group had a significantly longer surgery duration (P<0.05), but there was no significant statistical difference in terms of intraoperative blood loss, amount of bleeding, drainage tube removal time, postoperative length of hospitalization, incision suture removal time, or incidence of postoperative complications (P>0.05).

CONCLUSIONS

IORT using the Intrabeam system safely delivers radiation therapy, is well-tolerated, has acceptable acute toxicity, and does not significant increase the risk of surgery or the incidence of perioperative complications.

Polymorphism of DNA repair genes in breast cancer

Aim

The aim of the study was to determine the relationship between single nucleotide polymorphisms (SNPs) of DNA repair genes and modulation of the risk of breast cancer. The following SNPs were analysed: XRCC1-Arg399Gln (rs25487), hMSH2-Gly322Asp (rs4987188), XRCC2-Arg188His (rs3218536), XPD- Lys751Gln (rs13181), RAD51--4719A/T (rs2619679) and RAD51--4601A/G (rs5030789).

Material and Methods

The study included n = 600 patients: 300 with breast cancer and 300 healthy controls. The HRM (High-Resolution Melter) technique was applied for polymorphism analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each genotype and allele.

Results

Statistically significant correlations were identified between four single nucleotide polymorphisms and the breast cancer risk: XRCC1-Arg399Gln, hMSH2-Gly322Asp, XPD- Lys751Gln and RAD51--4719A/T. Allele XRCC1-Gln (OR 6.37; 95% CI 4.86-8.35, p < .0001), hMSH2-Asp (OR 4.41; 95% CI 3.43-5.67, p < .0001), XPD -Gln (OR 2.56; 95% CI 2.02-3.25, p < .0001) and RAD51-T genes (OR 1.44; 95% CI 1.15-1.80, p = 0.002) strongly correlated with breast carcinoma. No relationship was observed between the studied polymorphisms and the cancer progression grade according to Scarf-Bloom-Richardson classification.

Conclusions

The results implies that polymorphisms of DNA repair genes may be associated with breast cancer occurrence.

Association between single nucleotide polymorphism of DNA repair genes and endometrial cancer: a case-control study

Aim: The aim of this study was to analyse the frequencies of genotypes and alleles of Single Nucleotide Polymorphisms (SNPs) of six DNA repair genes (XRCC1-rs25487, XPD-rs13181, hMSH2-rs4987188, XRCC2-rs3218536, BRCA1-rs799917 and BRCA2-rs144848 SNPs) and attempt to evaluate the effect this DNA marker on endometrial cancer (EC). Material and methods: The patients were recruited to the study at the Department of Operative Gynaecology of the Institute of the Polish Mother's Memorial Hospital in Lodz. The study comprised 510 patients treated for EC. 510 disease-free individuals were used as controls. SNPs were analysed by the high resolutionmelting technique (HRM). Results: Statistically significant correlations were identified between four SNPs and endometrial cancer risk: rs25487, rs4987188, rs13181 and rs799917. The alleles XRCC1-Gln (OR 2.89; 95% CI 2.39-3.49, P<0.0001), hMSH2-Asp (OR 1.65; 95% CI 1.38-1.96, P<0.0001), XPD-Gln (OR 3.24; 95% CI 2.69-3.91, P<0.0001) and BRCA1-L (OR 1.56; 95% CI 1.31-1.85, P<0.0001) genes were strongly correlated with this malignancy. No relationship was found between the studied polymorphisms of XRCC2 and BRCA2 and the incidence of endometrial cancer. There was also not any association between polymorphisms of XRCC1, hMSH2, XPD, XRCC2, BRCA1, BRCA2, i.e., the polymorphisms of the analysed repair genes, and the cancer stage progression acc. to FIGO, the body mass index, the number of pregnancies in history, replacement therapy, diabetes mellitus and hypertension. Conclusions: The results indicate that rs25487, rs4987188, rs13181, and rs799917 SNPs may be associated with the incidence of endometrial cancer.

Data on Single Nucleotide Polymorphism of DNA Repair Genes and Breast Cancer Risk from Poland

Single nucleotide polymorphisms (SNPs) may modify the risk of cancer. They may be then regarded as potential markers of carcinogenesis. The aim of this study was to analyze the frequency of genotypes and alleles of SNPs in DNA repair genes and to investigate the influence this genetic variation exerts on breast cancer in Polish females. The test group comprised 600 females with breast cancer and 600 healthy controls. Genomic DNA was isolated and the SNPs in DNA repair genes were determined by High-Resolution Melter (HRM) technique. Following polymorphisms were analysed: Arg399Gln (rs25487) of the XRCC1, Gly322Asp (rs4987188) of the hMSH2, Lys751Gln (rs13181) of the XPD, Arg188His (rs3218536) of the XRCC2, P871L (rs799917) of the BRCA1 and N372H (rs144848) of the BRCA2 gene. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each genotype and allele. Statistically significant correlations were identified between 4 single nucleotide polymorphisms and the breast cancer risk: rs25487 rs4987188 rs13181 and rs799917. The alleles XRCC1-Gln (OR 5.11; 95% CI 5.68-11.64, p < .0001), hMSH2-Asp (OR 4.66; 95% CI 3.90-5.56, p < .0001), XPD-Gln (OR 2.65; 95% CI 2.24-3.14, p < .0001) and BRCA1-L (OR 1.45; 95% CI 1.24-1.71, p < .0001) genes were strongly correlated with this malignancy. No correlation was found between the studied SNPs and tumor grading nor the lymph node status. Further research on larger groups is warranted to determine the influence of above-mentioned genetic variants on breast cancer risk.

Polymorphisms and mutations in GSTP1, RAD51, XRCC1 and XRCC3 genes in breast cancer patients

BACKGROUND

Genotoxic factors, including ionizing radiation and oxidative stress, are associated with genomic instability and development of breast cancer (BC). The homologous recombination DNA repair (HRR) pathway, base excision repair (BER) mechanism, and antioxidative enzymes are required as defense mechanisms against these DNA damaging agents. GSTP1, XRCC1, XRCC3 and RAD51 proteins are essential components of antioxidation, BER and HRR of DNA, respectively. Deficiencies in BER, HRR and antioxidation pathways are involved in the progression of cancer.

METHODS

Genomic DNA was extracted from formalin-fixed, paraffin-embedded tissue and blood samples of BC patients of an Italian population. Genomic DNA was also extracted from blood specimens of a control group. DNA sequencing was performed for six single-nucleotide polymorphisms (SNPs) in the GSTP1, RAD51, XRCC1 and XRCC3 genes in BC patients and the control group.

RESULTS

Two variants in the 5'-UTR of the XRCC3 (rs1799794 A/G) and RAD51 (rs1801321) genes showed a significant association with susceptibility to BC (OR = 4.125; 95% CI 1.057-16.102; p = 0.03 and OR = 2.04; 95% CI 0.4925-8.449; p = 0.007, respectively). Additionally, we reported 2 mutations in intron 7 of the XRCC3 gene, CTdel (rs543072564) and A/G (rs369703243).

CONCLUSIONS

Our results underscored the existence of an association between XRCC3-5'-UTR-A/G (rs1799794) and RAD51-5'-UTR G172T (rs1801321) genotypes and BC risk in an Italian population. The presence of mutations in the intronic region of the XRCC3 gene highlights the importance of more sequence screening of DNA repair genes for possible genetic penetrance in BC.

Polymorphisms in RAD51 and their relation with breast cancer in Saudi females

The present study aimed at investigating the relationship between rs1801320 (G>C), rs1801321 (G>T), and rs2619681 (C>T) RAD51 gene polymorphisms and the risk of breast cancer development in Saudi females. The genotypes were analyzed using TaqMan genotyping assay and polymerase chain reaction-restriction fragment length polymorphism. The genotype and allele frequencies were computed using chi-square or Fisher’s exact test (two-tailed) by SPSS 21 software. The results showed that rs1801321G>T GG genotype and G allele frequency were strongly (P<0.0001) related to an elevated risk of breast cancer, while the mutant T allele appeared to provide protection against breast cancer development as observed from the significantly lower (P<0.0001) frequencies of the TT and GT genotypes in cancer patients compared to the healthy controls. The variant rs1801320G>C showed no significant differences in the frequencies of the genotypes and alleles in the patients and the control groups. The CC genotype and C allele frequency of rs2619681 (C>T) variant were significantly (P=0.012) higher in cancer patients, whereas the T allele showed a protective effect against cancer development. The frequencies of the three single-nucleotide polymorphisms did not differ in cancer patients with different tumor grades and human epidermal growth factor receptor 2 status (+ or −). However, the genotype frequency of rs1801320 (135G>C) differed in the patients with estrogen receptor (ER)+ and ER−, where CC genotype showed a significantly higher prevalence in the females with ER− who were suffering from breast cancer. In addition, the frequency of C allele of rs2619681 (C>T) was also significantly higher in the breast cancer patients who were ER+ and progesterone receptor (PR)+ compared to those with ER− and PR−. In the Saudi females, rs1801320 did not show an association with risk of breast cancer. Taken together, the results suggest that RAD51 rs1801321 polymorphism may be involved in the etiology of breast cancer in the Saudi females; however, further studies are necessary to confirm this relation.

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.

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.

Association between RAD51 polymorphism and breast cancer susceptibility: a meta analysis

BACKGROUND

RAD51 interacting with BRCA1 and BRCA2 could modulate the penetrance of BRCA1/BRCA2 mutations, which may increase susceptibility for breast cancer by inhibiting DNA repair and genome stability. The purpose of this study was to provide refined statistical evidence for the association between RAD51 polymorphism and breast cancer risk.

DESIGN AND RESULTS

We conducted a meta-analysis of 15 publications with a total of 11,766 cancer cases and 11,227 controls. We summarized the data on the association of RAD51 polymorphism with breast cancer risk and performed subgroup analyses by ethnicity and control source. The pooled ORs based on fixed-effects model did not indicate a modified risk of breast cancer associated with RAD51 polymorphism in the overall population. Nor did we find a significant association in any stratified analysis.

CONCLUSIONS

This meta-analysis suggested that RAD51 polymorphism did not appear to represent a significant risk factor for breast cancer.

Tumor-associated mutations in a conserved structural motif alter physical and biochemical properties of human RAD51 recombinase

Human RAD51 protein catalyzes DNA pairing and strand exchange reactions that are central to homologous recombination and homology-directed DNA repair. Successful recombination/repair requires the formation of a presynaptic filament of RAD51 on ssDNA. Mutations in BRCA2 and other proteins that control RAD51 activity are associated with human cancer. Here we describe a set of mutations associated with human breast tumors that occur in a common structural motif of RAD51. Tumor-associated D149N, R150Q and G151D mutations map to a Schellman loop motif located on the surface of the RecA homology domain of RAD51. All three variants are proficient in DNA strand exchange, but G151D is slightly more sensitive to salt than wild-type (WT). Both G151D and R150Q exhibit markedly lower catalytic efficiency for adenosine triphosphate hydrolysis compared to WT. All three mutations alter the physical properties of RAD51 nucleoprotein filaments, with G151D showing the most dramatic changes. G151D forms mixed nucleoprotein filaments with WT RAD51 that have intermediate properties compared to unmixed filaments. These findings raise the possibility that mutations in RAD51 itself may contribute to genome instability in tumor cells, either directly through changes in recombinase properties, or indirectly through changes in interactions with regulatory proteins.

The RAD51 135G>C polymorphism is related to the effect of adjuvant therapy in early breast cancer

PURPOSE

RAD51, a central player in the response to DNA damage, has been suspected to contribute to tumour resistance to therapy. A single-nucleotide polymorphism, RAD51 135G>C, in the untranslated region of the RAD51 gene elevates breast cancer risk among BRCA2 carriers. In this study, it was investigated whether this polymorphism is related to prognosis of breast cancer and RAD51 protein expression and whether it is indicative of resistance to radiotherapy or cyclophosphamide/methotrexate/5-fluorouracil (CMF) chemotherapy.

PATIENTS AND METHODS

We genotyped 306 patients with early breast cancer, who were randomised to receive post-operative radiotherapy or CMF chemotherapy, for the RAD51 135G>C polymorphism. RAD51 protein expression was evaluated with immunohistochemistry.

RESULTS

15.4 % of the patients had at least one C-allele (three were C homozygotes). There was no correlation between genotype and protein expression. Patients who were G homozygotes benefitted from radiotherapy with decreased risk of local recurrences (RR = 0.32, 95 % C.I. 0.16-0.64, p = 0.001). CMF chemotherapy reduced the risk of distant recurrence for patients carrying at least one C-allele (RR = 0.29, 95 % C.I. 0.10-0.88, p = 0.03), whereas G homozygotes had no benefit from chemotherapy. There was a significant interaction between chemotherapy and genotype (p = 0.02).

CONCLUSION

The results suggest that the RAD51 135G>C polymorphism predicts CMF chemotherapy effect in early breast cancer.

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

XRCC2 and XRCC3 genes involved in homologous recombination repair (HRR) of DNA and in the maintenance of the genome integrity play a crucial role in protecting against mutations that lead to cancer. The aim of the present work was to evaluate associations between the risk of triple-negative breast cancer (TNBC) and polymorphisms in the genes, encoding for two key proteins of HRR: XRCC2 Arg188His (c. 563 G>A; rs3218536, Genbank Accession Number NT 007914) and XRCC3 Thr241Met (c. 722 C>T; rs861539, Genbank Accession Number NT 026437). The polymorphisms of the XRCC2 and XRCC3 were investigated by PCR–RFLP in 70 patients with TNBC and 70 age- and sex-matched non-cancer controls. In the present work, a relationship was identified between XRCC2 Arg188His polymorphism and the incidence of triple-negative breast cancer. The 188His allele and 188His/His homozygous variant increased cancer risk. An association was confirmed between XRCC2 Arg188His and XRCC3 Thr241Met polymorphisms and TNBC progression, assessed by the degree of lymph node metastases and histological grades. In conclusion, XRCC2 Arg188His and XRCC3 Thr241Met polymorphisms may be regarded as predictive factors of triple-negative breast cancer in female population.

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.

BRCA1 polymorphisms and breast cancer epidemiology in the Western New York exposures and breast cancer (WEB) study

Results of studies for the association of BRCA1 genotypes and haplotypes with sporadic breast cancer have been inconsistent. Therefore, a candidate single nucleotide polymorphism (SNP) approach was used in a breast cancer case-control study to explore genotypes and haplotypes that have the potential to affect protein functions or levels. In a breast cancer case-control study, genotyping of BRCA1 polymorphisms Q356R, D693N, and E1038G was performed on 1,005 cases and 1,765 controls. Unconditional, polytomous logistic regression and χ(2) -tests were used to examine the associations of breast cancer with genotypes and haplotypes. In addition, interactions between genotype and smoking, benign breast disease, family history of breast cancer, body mass index (BMI), alcohol consumption, and hormonal risk factors, hormone receptor status, and breast cancer pathology were calculated also using logistic regression and χ(2) . Although sporadic breast cancer was not associated with BRCA1 genotypes or haplotypes overall or by menopausal status, there was evidence of an interaction between the E1038G BRCA1 genotype, smoking, and BMI among premenopausal women (P for interaction = 0.01 and 0.045, respectively) and between E1038G and D693N BRCA1 genotypes and hormone therapy use among postmenopausal women (P for interaction = 0.01 and 0.02, respectively). There were no other associations found between BRCA1 genotypes and stage, histological grade, or nuclear grade. However, the D693N SNP was associated with the risk of triple negative breast cancer (odds ratio = 2.31 95% confidence interval 1.08-4.93). The BRCA1 variants studied may play a role in the etiology of triple negative breast cancer and may interact with environmental factors such as hormone therapy or smoking and increase sporadic breast cancer risk.

DNA repair and cytotoxic drugs: the potential role of RAD51 in clinical outcome of non-small-cell lung cancer patients

Many of the cytotoxic drugs used in the treatment of non-small-cell lung carcinoma patients can interfere with DNA activity and the definition of an individual DNA repair profile could be a key strategy to achieve better response to chemotherapeutic treatment. Although DNA repair mechanisms are important factors in the prevention of carcinogenesis, these molecular pathways are also involved in therapy response. RAD51 is a crucial element in DNA repair by homologous recombination and has been shown to interfere with the prognosis of patients treated with chemoradiotherapy. There is increasing evidence that genetic polymorphisms in repair enzymes can influence DNA repair capacity and, consequently, affect chemotherapy efficacy. We conducted this review to show the possible influence of the RAD51 genetic variants in damage repair capacity and treatment response in non-small-cell lung carcinoma patients.

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.

Genetic variability of Xrcc3 and Rad51 modulates the risk of head and neck cancer

A case-control study was conducted to analyze the possible associations between the head and neck cancer (HNC) risk and fourteen single nucleotide polymorphisms (SNPs) and haplotypes in Xrcc3 and Rad51 genes. This study involved 81 HNC cases and 111 healthy control subjects. A significant risk-increasing effect of rs3212057 (p.Arg94His) SNP in Xrcc3 (OR=6.6; p<0.01) was observed. On the other hand, risk-decreasing effect was found for rs5030789 (g.3997A>G) and rs1801321 (c.-60G>T) in 5' near gene and 5'UTR regions of Rad51, respectively (OR=0.3 and OR=0.2, p<0.05, respectively). Moreover, these effects were shown to be modulated by tobacco-smoking status and gene-gene interactions. Concluding, the genetic variability of Xrcc3 and/or Rad51 genes might be of relevance with respect to HNC risk.

Unravelling modifiers of breast and ovarian cancer risk for BRCA1 and BRCA2 mutation carriers: update on genetic modifiers

Pathogenic mutations in the tumour suppressor genes BRCA1 and BRCA2 confer increased risks for breast and ovarian cancer and account for approximately 15% of the excess familial risk of breast cancer amongst first-degree relatives of patients with breast cancer. There is considerable evidence indicating that these risks vary by other genetic and environmental factors clustering in families. In the past few years, based on the availability of genome-wide association data and samples from large collaborative studies, several common alleles have been found to modify breast or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. These common alleles explain a small proportion of the genetic variability in breast or ovarian cancer risk for mutation carriers, suggesting more modifiers remain to be identified. We review the so far identified genetic modifiers of breast and ovarian cancer risk and consider the implications for risk prediction. BRCA1 and BRCA2 mutation carriers could be some of the first to benefit from clinical applications of common variants identified through genome-wide association studies. However, to be able to provide more individualized risk estimates, it will be important to understand how the associations vary with different tumour characteristics and their interactions with other genetic and environmental modifiers.

Modification of BRCA1-Associated Breast and Ovarian Cancer Risk by BRCA1-Interacting Genes

Inherited BRCA1 mutations confer elevated cancer risk. Recent studies have identified genes that encode proteins that interact with BRCA1 as modifiers of BRCA1-associated breast cancer. We evaluated a comprehensive set of genes that encode most known BRCA1 interactors to evaluate the role of these genes as modifiers of cancer risk. A cohort of 2,825 BRCA1 mutation carriers was used to evaluate the association of haplotypes at ATM, BRCC36, BRCC45 (BRE), BRIP1 (BACH1/FANCJ), CTIP, ABRA1 (FAM175A), MERIT40, MRE11A, NBS1, PALB2 (FANCN), RAD50, RAD51, RAP80, and TOPBP1, and was associated with time to breast and ovarian cancer diagnosis. Statistically significant false discovery rate (FDR) adjusted P values for overall association of haplotypes (P(FDR)) with breast cancer were identified at ATM (P(FDR) = 0.029), BRCC45 (P(FDR) = 0.019), BRIP1 (P(FDR) = 0.008), CTIP (P(FDR) = 0.017), MERIT40 (P(FDR) = 0.019), NBS1 (P(FDR) = 0.003), RAD50 (P(FDR) = 0.014), and TOPBP1 (P(FDR) = 0.011). Haplotypes at ABRA1 (P(FDR) = 0.007), BRCC45 (P(FDR) = 0.016 and P(FDR) = 0.005 in two haplotype blocks), and RAP80 (P(FDR) < 0.001) were associated with ovarian cancer risk. Overall, the data suggest that genomic variation at multiple loci that encode proteins that interact biologically with BRCA1 are associated with modified breast cancer and ovarian cancer risk in women who carry BRCA1 mutations.

Susceptibility of XPD and RAD51 genetic variants to carcinoma of urinary bladder in North Indian population

For the present study, two polymorphisms, xeroderma pigmentosum, complementation group D (XPD) Lys751Gln and RAD51 135G/C were studied with regard to bladder cancer. For XPD Lys751Gln polymorphism, an increased risk of bladder cancer was found to be associated with the Gln variant allele (odds ratio [OR]=1.86, 95% confidence interval [CI]=1.27-2.73), on taking AA (Lys/Lys) as the referent genotype. In males, the XPD 751C (Gln) allele was found to be associated with a significantly increased risk (OR=2.33, 95% CI=1.52-3.56). The inhabitants of rural areas showed a significantly increased risk with the XPD Gln allele (OR=2.59, 95% CI=1.46-4.62) when compared with those of urban areas. In smokers (OR=5.30, 95% CI=2.42-11.68), alcohol drinkers (OR=4.33, 95% CI=2.17-8.70), and nonvegetarians (OR=2.21, 95% CI=1.26-3.87), the XPD Gln allele showed a significantly increased risk toward bladder cancer. For RAD51 135G/C polymorphism, no significant difference was observed in the allelic and genotypic frequencies. Even after stratification, no significant association could be seen. After stratifying histopathologically, the RAD51 CC genotype was associted with decreased risk in subjects having superficial stage (OR=0.51, 95% CI=0.27-0.99) and with those having G2 grade (OR=0.24, 95% CI=0.09-0.62) of bladder cancer. XPD polymorphism may be a predisposing factor, but the same cannot be said for RAD51 gene polymorphism.

Association of Rad51 polymorphism with DNA repair in BRCA1 mutation carriers and sporadic breast cancer risk

BACKGROUND

Inter-individual variation in DNA repair capacity is thought to modulate breast cancer risk. The phenotypic mutagen sensitivity assay (MSA) measures DNA strand breaks in lymphocytes; women with familial and sporadic breast cancers have a higher mean number of breaks per cell (MBPC) than women without breast cancer. Here, we explore the relationships between the MSA and the Rad51 gene, which encodes a DNA repair enzyme that interacts with BRCA1 and BRCA2, in BRCA1 mutation carriers and women with sporadic breast cancer.

METHODS

Peripheral blood lymphoblasts from women with known BRCA1 mutations underwent the MSA (n = 138 among 20 families). BRCA1 and Rad51 genotyping and sequencing were performed to identify SNPs and haplotypes associated with the MSA. Positive associations from the study in high-risk families were subsequently examined in a population-based case-control study of breast cancer (n = 1170 cases and 2115 controls).

RESULTS

Breast cancer diagnosis was significantly associated with the MSA among women from BRCA1 families (OR = 3.2 95%CI: 1.5-6.7; p = 0.004). The Rad51 5'UTR 135 C>G genotype (OR = 3.64; 95% CI: 1.38, 9.54; p = 0.02), one BRCA1 haplotype (p = 0.03) and in a polygenic model, the E1038G and Q356R BRCA1 SNPs were significantly associated with MBPC (p = 0.009 and 0.002, respectively). The Rad51 5'UTR 135C genotype was not associated with breast cancer risk in the population-based study.

CONCLUSIONS

Mutagen sensitivity might be a useful biomarker of penetrance among women with BRCA1 mutations because the MSA phenotype is partially explained by genetic variants in BRCA1 and Rad51.

Association between single nucleotide polymorphisms in the XRCC1 and RAD51 genes and clinical radiosensitivity in head and neck cancer

PURPOSE

Individual variability in radiosensitivity is large in cancer patients. Single nucleotide polymorphisms (SNPs) in genes involved in DNA repair and in protection against reactive oxygen species (ROS) could be responsible for such cases of radiosensitivity. We investigated the association between the occurrence of acute reactions in 101 patients with squamous cell carcinoma of the head and neck (SCCHN) after radiotherapy (RT) and five genetic polymorphisms: XRCC1 c.1196A>G, XRCC3 c.722C>T, RAD51 (c.-3429G>C, c.-3392G>T), and GSTP1 c.313A>G.

MATERIALS AND METHODS

Genetic polymorphisms were detected by high resolution melting analysis (HRMA). The development of acute reactions (oral mucositis, skin erythema and dysphagia) associated with genetic polymorphisms was modeled using Cox proportional hazards, accounting for biologically effective dose (BED).

RESULTS

Development of grade ≥2 mucositis was increased in all patients (chemo-radiotherapy and radiotherapy alone) with XRCC1-399Gln allele (HR=1.72). The likelihood of developing grade ≥2 dysphagia was higher in carriers of RAD51 c.-3429 CC/GC genotypes (HR=4.00). The presence of at least one SNP or the co-presence of both SNPs in XRCC1 p.Gln399Arg /RAD51 c.-3429 G>C status were associated to higher likelihood of occurrence of acute toxicities (HR=2.03).

CONCLUSIONS

Our findings showed an association between genetic polymorphisms, XRCC1 c.1196A>G and RAD51 c.-3429 G>C, and the development of radiation-induced toxicities in SCCHN patients.

Genetic modifiers of cancer risk for BRCA1 and BRCA2 mutation carriers

Germline mutations in BRCA1 and BRCA2 confer high risks of female breast and ovarian cancer. However, there is strong evidence that these risks are modified by other factors, including familial or genetic factors. Genome-wide association studies have identified several breast cancer genetic susceptibility variants in the general population that are also associated with breast cancer risk for mutation carriers. The patterns of association for these variants vary between BRCA1 and BRCA2 mutation carriers and this variation appears to be driven by their differential associations with breast cancer subtypes defined by estrogen receptor status. We review the latest evidence regarding genetic modifiers of cancer risk for female BRCA1 and BRCA2 mutation carriers emerging from candidate gene studies, variants found in genome-wide association studies (GWAS) to be associated with cancer risk in the general population and GWAS specifically in mutation carriers. We also discuss the implications of these findings for cancer risk prediction in these women. BRCA1 and BRCA2 mutation carriers could potentially be among the first groups of individuals for whom clinically applicable risk profiling could be developed using the common breast cancer susceptibility variants identified through GWAS.

Prioritizing candidate genetic modifiers of BRCA1 and BRCA2 using a combinatorial analysis of global expression and polymorphism association studies of breast cancer

Epidemiological evidence from different studies has shown that genes harboring sequence variations may modify breast cancer risk in BRCA1 and BRCA2 mutation carriers. Current attempts to identify genetic modifiers of BRCA1 and BRCA2 associated risk have focused on a candidate gene-based approach or the development of large genome-wide association studies. However, both methods have notable limitations. This chapter describes a novel approach for analyzing gene expression differences to prioritize candidate modifier genes for single nucleotide polymorphism association studies. The advantage that gives this strategy an edge over other candidate gene-based studies is its potential to identify candidate genes that interact with exogenous risk factors to cause or modify cancer, without detailed a priori knowledge of the molecular pathways involved.

RAD51 135G/C polymorphism and breast cancer risk: a meta-analysis from 21 studies

Growing evidence suggests that RAD51 plays a pivotal role in the repair of DNA double-strand breaks and the maintenance of genomic stability. A single nucleotide polymorphism, 135G/C, has been identified in the 5' untranslated region of the RAD51 gene and has been shown to influence gene transcription activity. Previous studies yielded conflicting results as to the association of 135G/C polymorphism with breast cancer. We aimed to assess the effect of 135G/C of RAD51 on breast cancer susceptibility with the use of a meta-analysis. We performed a meta-analysis of 21 published case-control studies up to April 2010. We found that the CC genotype was associated with a significantly increased risk of breast cancer when compared with the GG, CG, and CG/GG genotypes. Subgroup analyses showed that individuals carrying the CC genotype were associated with an elevated tumor risk in European populations and in sporadic breast cancer. After stratified analyses according to manuscript quality, the CC genotype was associated with a significantly increased risk of breast cancer compared with the CG genotype in studies of both higher and lower quality. However, significantly elevated risk was found in studies of higher quality, but not in studies of lower quality when homozygote and a recessive comparison model were tested. This meta-analysis indicates that RAD51 135G/C polymorphism may be identified as a susceptibility locus for breast cancer.

RAD51 135G>C polymorphism and breast cancer risk: a meta-analysis

Mutations in RAD51 gene are believed to be associated with elevated breast cancer risk. However, several case-control studies focusing on the association between RAD51 135G>C and breast cancer risk failed to achieve consensus. To clarify the effect of RAD51 135G>C polymorphism on breast cancer, a meta-analysis was performed. By searching PubMed and EMBASE, a total of 14 case-control studies, containing 12,183 cases and 10,183 controls, were included. The strength of association between RAD51 135G>C polymorphism and breast cancer risk was assessed by odds ratio (OR) with the corresponding 95% confidence interval (95% CI). When all the eligible studies were pooled into the meta-analysis, an elevated cancer risk was revealed in additive model (OR, 1.34; 95% CI, 1.01-1.78; P = 0.044) and recessive model (OR, 1.37; 95% CI, 1.03-1.82; P = 0.032). In subgroup analyses by ethnicity, BRCA1/2 mutation status, and family history, a significant association was found only among BRCA2 mutation carriers (additive model: OR, 4.92; 95% CI, 1.11-21.83; P = 0.036; recessive model: OR, 4.88; 95% CI, 1.10-21.67; P = 0.037). Sensitivity analysis did not perturb the results. In conclusion, this meta-analysis suggests that RAD51 variant 135C homozygote is associated with elevated breast cancer risk among BRCA2 mutation carriers.

RAD51 135G>C does not modify breast cancer risk in non-BRCA1/2 mutation carriers: evidence from a meta-analysis of 12 studies

A single-nucleotide polymorphism (SNP) in the 5'-untranslated region (UTR) of RAD51, 135G>C (rs1801320), was reported to be associated with an increased risk of breast cancer among BRCA2 as well as BRCA1 carriers. A few studies have also investigated the genetic contribution of RAD51 135G>C to the risk of sporadic breast cancers or breast cancer in non-BRCA1/2 carriers, though the results are yet controversial and inconclusive. We, in this study, performed a more precise estimation of the relationship between 135G>C and breast cancer among non-BRCA1/2 mutation carriers by meta-analyzing the currently available evidence from the literature. A total of 12 studies involving 7,065 cases and 6,981 controls were identified. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. When all the studies were pooled into the meta-analysis, there was no evidence for a significant association between 135G>C and breast cancer risk in non-BRCA1/2 mutation carriers (for CC vs. GG: OR = 0.995, 95%CI: 0.741-1.336; for GC vs. GG: OR = 0.959, 95%CI: 0.869-1.057; for dominant model: OR = 0.988, 95%CI: 0.902-1.082; and for recessive model: OR = 1.037, 95%CI: 0.782-1.376). We also performed subgroup analysis by ethnicity (Caucasian) as well as did analysis using the studies fulfilling Hardy-Weinberg equilibrium, and the results did not change. In summary, the present meta-analysis suggests that the RAD51 135G>C does not modify breast cancer risk in non-BRCA1/2 mutation carriers.

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

Several studies have investigated the associations between RAD51 G135C polymorphism and the susceptibility to breast cancer, but results have been inconclusive. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 17 case control studies, including 12,153 cases and 10,245 controls, were selected. Overall, significant decreased risk was found for the additive model (OR = 0.995, 95% CI = 0.991-0.998) and dominant model (OR = 0.994, 95% CI = 0.991-0.998). In the subgroup analysis by ethnicity, statistically significantly decreased risk was found in Asians (additive model: OR = 0.977, 95% CI = 0.954-1.000 and dominant model: OR = 0.981, 95% CI = 0.963-1.000). In conclusion, this meta-analysis suggests that the RAD51 G135C polymorphism is a low-penetrant risk factor for developing breast cancer.

Influence of DNA repair RAD51 gene variants in overall survival of non-small cell lung cancer patients treated with first line chemotherapy

PURPOSE

Lung cancer continues to be the most frequent cancer with approximately one million people worldwide dying of this disease each year. Non-small-cell lung cancer (NSCLC) accounts for approximately 80% of all lung cancers. The RAD51 protein is the key protein for homologous recombination, an evolutionarily conserved mechanism for DNA damage repair and the generation of genetic diversity. We conducted this study in order to investigate the effect of the RAD51 G135C polymorphism in treatment response to combined platinum taxanes/gemcitabine first line chemotherapy in NSCLC patients.

METHODS

We analysed RAD51 G135C polymorphism in 243 NSCLC patients using PCR-RFLP methodology.

RESULTS

There were no statistically significant differences between the groups of NSCLC patients with the different genotypes regarding tumour stage (p = 0.232). Our results indicate that the mean survival rates were statistically different according to the patient's genotypes. The group of patients carrying the C allele presented a higher mean survival rate than the other patients (56.0 months vs. 41.7 months; p = 0.024). Moreover, regarding smoking history, our results demonstrate that overall survival time differed significantly according to the patient's genotypes in smoker and ex-smoker individuals (p = 0.034). No statistically significant differences were found in the genotype frequencies and overall survival rate among non-smoker NSCLC patients (p = 0.413).

CONCLUSIONS

This is the first study evaluating the effect of the RAD51 G135C polymorphism in NSCLC patient survival. Our results suggest that RAD51 genotypes could be useful molecular markers for predicting the clinical outcome of NSCLC patients.

Modification of ovarian cancer risk by BRCA1/2-interacting genes in a multicenter cohort of BRCA1/2 mutation carriers

Inherited BRCA1/2 mutations confer elevated ovarian cancer risk. Knowledge of factors that can improve ovarian cancer risk assessment in BRCA1/2 mutation carriers is important because no effective early detection for ovarian cancers exists. A cohort of 1,575 BRCA1 and 856 BRCA2 mutation carriers was used to evaluate haplotypes at ATM, BARD1, BRIP1, CTIP, MRE11, NBS1, RAD50, RAD51, and TOPBP1 in ovarian cancer risk. In BRCA1 carriers, no associations were observed with ATM, BARD1, CTIP, RAD50, RAD51, or TOPBP1. At BRIP1, an association was observed for one haplotype with a multiple testing corrected P (P(corr)) = 0.012, although no individual haplotype was significant. At MRE11, statistically significant associations were observed for one haplotype (P(corr) = 0.007). At NBS1, we observed a P(corr) = 0.024 for haplotypes. In BRCA2 carriers, no associations were observed with CTIP, NBS1, RAD50, or TOPBP1. Rare haplotypes at ATM (P(corr) = 0.044) and BARD1 (P(corr) = 0.012) were associated with ovarian cancer risk. At BRIP1, two common haplotypes were significantly associated with ovarian cancer risk (P(corr) = 0.011). At MRE11, we observed a significant haplotype association (P(corr) = 0.012), and at RAD51, one common haplotype was significantly associated with ovarian cancer risk (P(corr) = 0.026). Variants in genes that interact biologically withBRCA1 and/or BRCA2 may be associated with modified ovarian cancer risk in women who carry BRCA1/2 mutations.

Associations between single nucleotide polymorphisms in double-stranded DNA repair pathway genes and familial breast cancer

PURPOSE

DNA damage recognition and repair play a major role in risk for breast cancer. We investigated 104 single nucleotide polymorphisms (SNP) in 17 genes whose protein products are involved in double-stranded break repair (DSBR).

EXPERIMENTAL DESIGN

We used a case-control design. Both the case individuals affected with breast cancer or with both breast and ovarian cancers and the controls had similar familial risk of breast cancer and were participants in a high-risk cancer registry.

RESULTS

We found that 12 of the polymorphisms are associated with breast or breast and ovarian cancers, most notably rs16888927, rs16888997, and rs16889040, found in introns of RAD21, suggesting that SNPs in other genes in the DSBR pathway in addition to BRCA1 and BRCA2 may affect breast cancer risk.

CONCLUSIONS

SNPs within or near several DSBR DNA repair pathway genes are associated with breast cancer in individuals from a high-risk population. In addition, our study reemphasizes the unique perspective that recruitment of cases and controls from family cancer registries has for gene discovery studies.

Effects of the single nucleotide polymorphism at MDM2 309 on breast cancer patients with/without BRCA1/2 mutations

BACKGROUND

A germ line single nucleotide polymorphism (SNP) in the first intron of the gene encoding MDM2 at position 309, an important modulator of p53, has been described. BRCA1/2 mutation have been associated with increased rates of breast cancers with mutated P53. It was shown that the presence of MDM2 309 SNP correlated with younger cancer onset age in individuals with a p53 mutations. The differential effects of this SNP were also linked to estrogen receptor activation. Here we report on our study of 453 Ashkenazi breast cancer patients of whom 180 were positive for the known Ashkenazi BRCA1/2 mutations

METHODS

DNA from breast cancer patients was obtained for analysis of one of the three common BRCA1/2 mutations and MDM2 SNP309. Data regarding cancer onset and death ages was obtained from our database and Statistical analysis was performed using the SPSS statistical package (SPCC Inc., Chicago, IL), and JMP software (SAS Institute, Cary, NC).

RESULTS

The percentage of MDM2 SNP309 in control and BRCA 1/2 population which is similar to that reported for other Jewish Ashkenazi populations at 52.2% for the heterozygotes and 25.0% for MDM2SNP309G/G and 22.8% for MDM2SNP309T/T.There was not a statistical significant difference in median age of disease onset in the different MDM2 SNP309 subgroups of the BRCA1/2 carriers. When we further divided the group into under and above 51 years old ( presumed menopause age) in the BRCA1 positive subset we found that there were less patients of the MDM2SNP309 G/G versus the MDM2SNP309 T/T in the over 51 patient group (p = 0.049). This result has been obtained in a relatively small subgroup and is of borderline statistical significance. Interestingly, in the BRCA1/2 mutation carriers, we found a survival advantage for patients harboring the SNP309 G/G genotype (p = 0.0086) but not for the 272 patients not harbouring this mutations.

CONCLUSION

MDM2SNP309G/G main effect on BRCA1/2 positive mutation carriers is linked to its effect on patients survival. Further research is needed in order to understand the reason for this difference.

Breast cancer susceptibility: current knowledge and implications for genetic counselling

Breast cancer is the most common malignancy in women in the Western world. Except for the high breast cancer risk in BRCA1 and BRCA2 mutation carriers as well as the risk for breast cancer in certain rare syndromes caused by mutations in TP53, STK11, PTEN, CDH1, NF1 or NBN, familial clustering of breast cancer remains largely unexplained. Despite significant efforts, BRCA3 could not be identified, but several reports have recently been published on genes involved in DNA repair and single nucleotide polymorphisms (SNPs) associated with an increased breast cancer risk. Although candidate gene approaches demonstrated moderately increased breast cancer risks for rare mutations in genes involved in DNA repair (ATM, CHEK2, BRIP1, PALB2 and RAD50), genome-wide association studies identified several SNPs as low-penetrance breast cancer susceptibility polymorphisms within genes as well as in chromosomal loci with no known genes (FGFR2, TOX3, LSP1, MAP3K1, TGFB1, 2q35 and 8q). Some of these low-penetrance breast cancer susceptibility polymorphisms also act as modifier genes in BRCA1/BRCA2 mutation carriers. This review not only outlines the recent key developments and potential clinical benefit for preventive management and therapy but also discusses the current limitations of genetic testing of variants associated with intermediate and low breast cancer risk.

Genetic variations in DNA repair genes, radiosensitivity to cancer and susceptibility to acute tissue reactions in radiotherapy-treated cancer patients

Ionizing radiation is a well established carcinogen for human cells. At low doses, radiation exposure mainly results in generation of double strand breaks (DSBs). Radiation-related DSBs could be directly linked to the formation of chromosomal rearrangements as has been proven for radiation-induced thyroid tumors. Repair of DSBs presumably involves two main pathways, non-homologous end joining (NHEJ) and homologous recombination (HR). A number of known inherited syndromes, such as ataxia telangiectasia, ataxia-telangiectasia like-disorder, radiosensitive severe combined immunodeficiency, Nijmegen breakage syndrome, and LIG4 deficiency are associated with increased radiosensitivity and/or cancer risk. Many of them are caused by mutations in DNA repair genes. Recent studies also suggest that variations in the DNA repair capacity in the general population may influence cancer susceptibility. In this paper, we summarize the current status of DNA repair proteins as potential targets for radiation-induced cancer risk. We will focus on genetic alterations in genes involved in HR- and NHEJ-mediated repair of DSBs, which could influence predisposition to radiation-related cancer and thereby explain interindividual differences in radiosensitivity or radioresistance in a general population.