Abstract 2030: A novel role for the 185delAG BRCA1 mutant protein, BRAT, in ovarian cancer pathology

Abstract

Objective: Familial history is the strongest risk factor for developing ovarian cancer (OC) and is associated with BRCA1 truncation mutations, such as the founder mutation 185delAG. Studying these risk-associated mutations may reveal signaling pathways important in OC etiology. Normal human ovarian surface epithelial (HOSE) cells expressing the 185delAG mutant, BRAT, exhibit phenotypic changes due, in part, to up-regulation of maspin, a tumor suppressor important in apoptosis, invasion, and metastasis that exhibits unique up-regulation in some cancer types. In the current study, we determined BRAT's impact on expression of Interleukin-1beta (IL1β), another key player in invasion and metastasis. Methods: HOSE cells transiently and stably expressing the 185delAG mutation and HOSE cells with endogenous 185delAG were analyzed for differential target gene expression by semi-quantitative, real time PCR, western blot; as well as, IL1β bioactivity. Western blot was used to identify cell signaling targets of BRAT mediated IL1β expression via MAPK pathways. Breast epithelial and breast cancer cells transiently and stably expressing BRAT were evaluated by real time PCR to determine whether BRAT induced IL1β is tissue specific. Results: BRAT-expressing HOSE cells exhibited enhanced IL1β mRNA expression. Higher levels of pro-IL1β protein were detected by Western blotting of cell lysate and conditioned media. Increased phosphorylation of MAPK pathway constituents were seen in BRAT-expressing HOSE cells as detected by Western blotting of cell lysate. However, expression of BRAT in normal breast and breast cancer cell lines failed to significantly alter IL1β expression levels. Conclusion: Normal HOSE cells expressing the BRAT mutation exhibit increased expression of IL1β. Further investigation is warranted to elucidate the mechanism of tissue-specific BRAT-mediated IL1β expression since increased IL1β expression may represent an early step of malignant transformation contributing to ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2030. doi:10.1158/1538-7445.AM2011-2030