Abstract 1852: A novel role for the 185delAG BRCA1 mutant protein, BRAT, in ovarian cancer pathology

Abstract

Abstract Objective: Familial history is the strongest risk factor for developing ovarian cancer (OC). Studying risk-associated BRCA1 truncation mutations, such as the founder mutation 185delAG, may reveal signaling pathways important in OC etiology. Normal human ovarian surface epithelial (HOSE) cells expressing the 185delAG mutant, BRAT, exhibit phenotypic changes due possibly 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 wish to determine BRAT's impact on expression and activity of matrix metalloprotease 1 (MMP1), another key player in invasion and metastasis, and the mechanism of this modulation. Methods: HOSE, breast epithelial cells, and breast cancer cells transiently and stably expressing the 185delAG mutation were analyzed for differential target gene expression by semi-quantitative and real time PCR. SiRNA transfection was performed to achieve knockdown of c-Jun. Western blotting was used to evaluate MMP1 and c-Jun protein levels. FRET ELISA was performed on conditioned media to evaluate levels and functionality of secreted MMP1. Cells were treated with cisplatin and subjected to MTS assay to evaluate chemosensitivity. Results: BRAT-expressing HOSE cells exhibited enhanced MMP1 mRNA expression. Higher levels of pro-MMP1 protein were detected by Western blotting of conditioned media. FRET ELISA revealed total MMP1 (pro and active forms) was also higher in BRAT-expressing cells, and that MMP1 in the conditioned media was functional. c-Jun knockdown diminished MMP-1 expression and secretion in HOSE. Expression of BRAT in normal breast and breast cancer cell lines failed to significantly alter chemosensitivity or MMP1 expression levels. Conclusion: Normal HOSE cells expressing the BRAT mutation exhibit c-Jun-dependent changes in expression of MMP1. Further investigation is warranted to elucidate the mechanism of this change since increased expression of this gene may represent an initial step forward on the continuum of malignant transformation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1852.