The role of the breast cancer susceptibility gene 1 (BRCA1) in sporadic epithelial ovarian cancer.

Mutations within the BRCA1 tumor suppressor gene occur frequently in familial epithelial ovarian carcinomas but they are a rare event in the much more prevalent sporadic form of the disease. However, decreased BRCA1 expression occurs frequently in sporadic tumors, and the magnitude of this decrease has been correlated with increased disease progression. The near absence of somatic mutations consequently suggests that there are alternative mechanisms that may contribute to the observed loss of BRCA1 in sporadic tumors. Indeed, both allelic loss at the BRCA1 locus and epigenetic hypermethylation of the BRCA1 promoter play an important role in BRCA1 down-regulation; yet these mechanisms alone or in combination do not always account for the reduced BRCA1 expression. Alternatively, misregulation of specific upstream factors that control BRCA1 transcription may be a crucial means by which BRCA1 is lost. Therefore, determining how regulators of BRCA1 expression may be co-opted during sporadic ovarian tumorigenesis will lead to a better understanding of ovarian cancer etiology and it may help foster the future development of novel therapeutic strategies aimed at halting ovarian tumor progression.