BRCA1 expression in a large series of sporadic ovarian carcinomas: a Gynecologic Oncology Group study.

BRCA1 is a tumor suppressor gene that, when mutated, is associated with the development of hereditary ovarian cancer. A role for BRCA1 in the pathoetiology of sporadic ovarian epithelial cancer (OEC) development has been suggested, although spontaneous mutations of the BRCA1 gene in this disease are uncommon. Loss of gene function by epigenetic alteration is observed more commonly, while other means of gene inactivation have not been intensively investigated. We examined expression and localization of the BRCA1 gene product by immunohistochemistry and sought to clarify the relationship between protein expression and tumor stage, grade, histopathologic subtype, and outcome. Among 230 spontaneous OEC tumors, we found a statistically significant decrease in BRCA1 protein expression with advancing stages of OEC. There was no relationship between expression and tumor grade. There was a statistically significant relationship between the pathologic subtypes of OEC and BRCA1 expression. Minimal BRCA1 expression was protective for survival. These findings confirm a high rate of loss of BRCA1 protein expression in sporadic OEC and suggest a role of BRCA1 in the progression of sporadic ovarian carcinoma.