BRCA1 as a predictive marker of survival in sporadic ovarian cancer
5512 Background: First line treatment of ovarian cancer (OC) involves both Platinum and Taxane based chemotherapy and reduced BRCA1 mRNA and protein expression levels are observed in up to 70% of sporadic ovarian tumours. We, therefore, investigated whether BRCA1 may represent a biomarker of response to chemotherapy in sporadic ovarian cancer. Methods: As in vitro models of sporadic ovarian cancer, we used both antisense and siRNA to abrogate BRCA1 expression in BG-1 and OVCAR5 ovarian cancer cells, respectively. Apoptotic responses to DNA damaging agents and antimicrotubule agents were measured using dose inhibition assays and Annexin V flow cytometry. Quantitiative real time PCR analysis (qRTPCR) was employed to measure BRCA1 mRNA expression in 54 surgically resected ovarian tumours. Univariate analysis provided an evaluation of the effect of BRCA1 mRNA expression and response to platinum or platinum/Taxane containing chemotherapy. Results: We provide in vitro evidence that BRCA1 differentially modulates chemosensitivity in sporadic ovarian cancer. Specifically, we demonstrate that antisense and siRNA inhibition of BRCA1 expression in both BG1 and OVCAR5 ovarian cancer cells, respectively, results in increased sensitivity to both cisplatin and carboplatin and decreased apoptotic response to both paclitaxel and docetaxel. Subsequently, by retrospective clinical analysis of 54 fresh frozen sporadic ovarian tumours we demonstrate that patients with low levels of BRCA1 have a significantly improved overall survival when treated with a platinum based chemotherapy regimen in comparison to patients with high levels of BRCA1 (30.4 months vs 21 months, p=0.047, HR 0.5). In addition, overall median survival for high BRCA1 expressing patients was found to double upon the addition of a taxane containing regimen (46.82 months vs 21 months, p=0.068, HR 0.44). Conclusions: We demonstrate both in vitro and in vivo evidence to support a role for BRCA1 as a predictive marker of response to chemotherapy in sporadic ovarian cancer. We believe that this study is significant given the high incidence of reduced BRCA1 mRNA and protein levels observed in sporadic ovarian cancer and may therefore have implications for the future management of this disease. No significant financial relationships to disclose.