Functional validation of a genome-wide association study (GWAS) SNP associated with anthracycline-induced congestive heart failure

Anthracyclines are commonly used chemotherapies for the treatment of breast cancer, but they can cause dose-related cardiotoxicities and lead to congestive heart failure (CHF) in ~2% of patients. There are no clinically available predictive biomarkers for this toxicity. Previously we have identified and validated the association of a single nucleotide polymorphism (SNP), rs28714259, with CHF in three large adjuvant phase III breast cancer trials. rs28714259 locates in a putative glucocorticoid receptor (GR) binding site and the risk (minor) allele is predicted to disrupt GR binding. Interestingly, activation of GR-signaling by dexamethasone has been shown to protect cardiomyocytes from doxorubicin-induced apoptosis in rat. To test whether the risk allele affects GR binding efficiency in vitro, we performed electrophoretic mobility shift assay (EMSA) in MCF-7 and A549 cells. 100nM of dexamethasone for 4 hours induced a prominent band shift in either the major- or risk-allele probes. Notably, we observed a ~50% reduction in the shifted band intensity of risk-allele probes compared to major-allele probes, suggesting decreased binding in risk-allele probes. No additional supershift was detected after the binding reaction was co-incubated with a GR antibody. However, the previously shifted band was significantly diminished in both the major- and risk-allele probes, probably due to a conformational change induced by GR antibody and leading to the disruption of GR/DNA binding, which in turn suggests the observed shift was specifically caused by GR. Further validations are ongoing using cardiomyocytes derived from human induced pluripotent stem cells (iPSCs). These studies provide further insight into the function and role of rs28714259 in anthracycline-induced CHF. Citation Format: Xi Wu, Gloria Xue, Laura Gardner, Fei Shen, Guanglong Jiang, Santosh Philips, Geneva Cunningham, Bryan P. Schneider. Functional validation of a genome-wide association study (GWAS) SNP associated with anthracycline-induced congestive heart failure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3882.