BRCA1 is an essential regulator of heart function and survival following myocardial infarction

Association of OX40L polymorphisms with sporadic breast cancer in northeast Chinese Han population

OX40L is an important costimulatory molecule that plays a crucial role in the regulation of T-cell-mediated immunity. The interaction of OX40-OX40L is involved in the pathogenesis of multiple autoimmune and inflammatory diseases such as systemic lupus erythematosus (SLE), carotid artery disease and cancer. The genetic variants of OX40L can increase the risk of SLE, atherosclerosis, systemic sclerosis and show gender-specific effects in some studies. Accordingly, we performed a case-control study including 557 breast cancer patients and 580 age- and sex-matched healthy controls to investigate whether single nucleotide polymorphisms (SNPs) in the OX40L gene are associated with sporadic breast cancer susceptibility and progression in Chinese Han women. Seven SNPs of OX40L (rs6661173, rs1234313, rs3850641, rs1234315, rs12039904, rs844648 and rs10912580) were genotyped with the method of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results indicated that rs3850641G allele could increase the susceptibility to breast cancer (P = 0.009662), even in the validation study (P = 0.0001515). A significant association between rs3850641 and breast cancer risk was observed under the additive model and dominant model (P = 0.01042 and 0.01942, respectively). The haplotype analysis showed that haplotype A(rs844648)A(rs10912580) was significantly associated with breast cancer, even after 10,000 permutations for haplotypes in block only (P = 0.0003). In clinicopathologic features analysis, the association between rs1234315 and C-erbB2 status was significant (P = 0.02541). Our data primarily indicates that rs3850641 of OX40L gene contributes to sporadic breast carcinogenesis in a northeast Chinese Han population.

BRCA2 variants and cardiovascular disease in a multi-ethnic study

Background

Germline mutations of BRCA1/2 are associated with hereditary breast and ovarian cancer. Recent data suggests excess mortality in mutation carriers beyond that conferred by neoplasia, and recent in vivo and in vitro studies suggest a modulatory role for BRCA proteins in endothelial and cardiomyocyte function. We therefore tested the association of BRCA2 variants with clinical cardiovascular disease (CVD).

Methods

Using data from 1,170 individuals included in two multi-ethnic population-based studies (SHARE and SHARE-AP), the association between BRCA2 variants and CVD was evaluated. 15 SNPs in BRCA2 with minor allele frequencies (MAF) > 0.01 had been previously genotyped using the cardiovascular gene-centric 50 k SNP array. 115 individuals (9.8%) reported a CVD event, defined as myocardial infarction (MI), angina, silent MI, stroke, and angioplasty or coronary artery bypass surgery. Analyses were adjusted for age and sex. The SNPs rs11571836 and rs1799943 were subsequently genotyped using the MassARRAY platform in 1,045 cases of incident MI and 1,135 controls from the South Asian subset of an international case-control study of acute MI (INTERHEART), and rs11571836 was imputed in 4,686 cases and 4500 controls from the Pakistan Risk of Myocardial Infarction Study (PROMIS).

Results

Two BRCA2 SNPs, rs11571836 and rs1799943, both located in untranslated regions, were associated with lower risk of CVD (OR 0.47 p = 0.01 and OR 0.56 p = 0.03 respectively) in the SHARE studies. Analysis by specific ethnicities demonstrated an association with CVD for both SNPs in Aboriginal People, and for rs11571836 only in South Asians. No association was observed in the European and Chinese subgroups. A non-significant trend towards an association between rs11571836 and lower risk of MI was observed in South Asians from INTERHEART [OR = 0.87 (95% CI: 0.75-1.01) p = 0.068], but was not evident in PROMIS [OR = 0.96 (95% CI: 0.90-1.03) p = 0.230]. Meta-analysis of both case-control studies resulted in a combined OR of 0.94 (95% CI: 0.89-1.004, p = 0.06).

Conclusions

Although there was an association between two SNPs in BRCA2 and CVD in a multi-ethnic population, these results were not replicated in two South Asian case-control studies of incident MI. Future studies exploring the association between BRCA variants and cardiovascular disorders are needed to clarify the role, if any, for BRCA variants in CVD pathogenesis.

BRCA2 protein deficiency exaggerates doxorubicin-induced cardiomyocyte apoptosis and cardiac failure

The tumor suppressor breast cancer susceptibility gene 2 (BRCA2) plays an important role in the repair of DNA damage, and loss of BRCA2 predisposes carriers to breast and ovarian cancers. Doxorubicin (DOX) remains the cornerstone of chemotherapy in such individuals. However, it is often associated with cardiac failure, which once manifests carries a poor prognosis. Because BRCA2 regulates genome-wide stability and facilitates DNA damage repair, we hypothesized that loss of BRCA2 may increase susceptibility to DOX-induced cardiac failure. To this aim, we generated cardiomyocyte-specific BRCA2 knock-out (CM-BRCA2(-/-)) mice using the Cre-loxP technology and evaluated their basal and post-DOX treatment phenotypes. Although CM-BRCA2(-/-) mice exhibited no basal cardiac phenotype, DOX treatment resulted in markedly greater cardiac dysfunction and mortality in CM-BRCA2(-/-) mice compared with control mice. Apoptosis in left ventricular (LV) sections from CM-BRCA2(-/-) mice compared with that in corresponding sections from wild-type (WT) littermate controls was also significantly enhanced after DOX treatment. Microscopic examination of LV sections from DOX-treated CM-BRCA2(-/-) mice revealed a greater number of DNA double-stranded breaks and the absence of RAD51 focus formation, an essential marker of double-stranded break repair. The levels of p53 and the p53-related proapoptotic proteins p53-up-regulated modulator of apoptosis (PUMA) and Bax were significantly increased in samples from CM-BRCA2(-/-) mice. This corresponded with increased Bax to Bcl-2 ratios and elevated cytochrome c release in the LV sections of DOX-treated CM-BRCA2(-/-) mice. Taken together, these data suggest a critical and previously unrecognized role of BRCA2 as a gatekeeper of DOX-induced cardiomyocyte apoptosis and susceptibility to overt cardiac failure. Pharmacogenomic studies evaluating cardiac function in BRCA2 mutation carriers treated with doxorubicin are encouraged.