title: BRCA1 185delAG truncation protein, BRAt, amplifies caspase-mediated apoptosis in ovarian cells.
abstract: Breast and ovarian cancer patients with germline mutations in BRCA1 respond more favorably to initial chemotherapy. We previously reported that cells from women carrying the BRCA1 185delAG founder mutation undergo an enhanced caspase-3-mediated apoptotic response. Here, we report on the transient and stable transfection of cDNA coding for the putative truncated protein product of the BRCA1 185delAG mutant gene into BRCA1 wild-type human ovarian surface epithelial cells and ovarian cancer cells, resulting in cells with a heterozygous background containing two BRCA1 wild-type alleles and the BRCA1 185delAG transcript. The BRCA1 185delAG truncation (BRAt) protein did not alter epithelial cell morphology or induce tumorigenesis. However, upon treatment with staurosporine, BRAt cells showed increased levels of active caspase-3 and increased cleavage of caspase-3 substrates, PARP and DFF45. Additionally, XIAP and cIAP-1 protein are at reduced levels in untreated BRAt cells as compared to control cells. BRAt also reduced levels of phosphorylated Akt and overexpression of activated Akt in BRAt cells restored caspase-3 activity to that seen in wild-type cells. Further, BRAt expression increased chemosensitivity in platinum-resistant ovarian cancer cells. Taken together, our data demonstrate that truncated proteins arising from BRCA1 185delAG mutation increase Akt-mediated apoptosis, suggesting a possible mechanism by which ovarian cancer patients with this germline BRCA1 mutation may respond better to initial chemotherapy.
authors.affiliation: Department of Pathology and Cell Biology, College of Medicine, University of South Florida, MDC Box 11, Tampa, FL 33612, USA.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: O'Donnell
authors.forename: Nicole C
authors.initials: NC
authors.lastname: Johnson
authors.forename: Tracy D
authors.initials: TD
authors.lastname: Turbeville
authors.forename: Michelle Y
authors.initials: MY
authors.lastname: Alfonso
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Kruk
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics*; D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D020169:Caspases / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D019313:BRCA1 Protein; D051034:Inhibitor of Apoptosis Proteins; D012333:RNA, Messenger; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C494833:BIRC2 protein, human; D044767:Ubiquitin-Protein Ligases; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases