BRCA1 185delAG mutant protein, BRAt, up-regulates maspin in ovarian epithelial cells.
OBJECTIVE
Aggressive clinical course and difficult detection of ovarian cancer are major challenges to improving patient survival and necessitate avid investigation into more effective therapeutic approaches. Understanding early molecular and pathological changes in high risk patients, such as BRCA1 mutation carriers, can provide candidates for molecular profiling and novel targets for effective therapies.


METHODS
Using a culture model system for normal human ovarian surface epithelial cells with and without the BRCA1 185delAG frameshift mutation for the truncated protein product, BRAt, we investigated the role of BRAt in enhanced chemosensitivity. We used MTS, Western immunoblot, semi-quantitative RT-PCR, luciferase reporter and siRNA assays, to identify novel downstream targets of BRAt that promote apoptosis following chemotherapeutic treatment.


RESULTS
We identified maspin as a novel downstream target of BRAt. BRAt increases maspin expression with preferential nuclear localization of maspin. Further, Brat-mediated maspin expression is transcriptionally regulated through an AP1 site within the (-520) to (-297) region of the promoter. Lastly, BRAt, enhances chemosensitivity in normal ovarian surface epithelial cells through c-Jun by a mechanism that may involve maspin.


CONCLUSIONS
BRAt-mediated enhanced chemosensitivity correlates clinically with enhanced chemotherapeutic response in BRCA1 mutation carriers. BRAt-mediated maspin expression also correlates with improved prognostic outlook for ovarian tumors with high levels of nuclear maspin. Consequently, understanding early genotypic and phenotypic changes in the context of high risk disease may provide a better understanding of the mechanism of mutation-associated ovarian cancer and provide new targets for therapeutic intervention.
O'Donnell
Joshua D
JD
Department of Pathology and Cell Biology, College of Medicine, University of South Florida,Tampa, FL 33612, USA.
Linger
Rebecca J
RJ
Kruk
Patricia A
PA
D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D005260:Female; D016368:Frameshift Mutation; D019398:Genes, BRCA1; D006801:Humans; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D015843:Serpins / Q000096:biosynthesis / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D019313:BRCA1 Protein; C492913:BRCA1 protein, human; C085344:SERPIN-B5; D015843:Serpins; D018808:Transcription Factor AP-1