title: Mechanisms underlying p53 regulation of PIK3CA transcription in ovarian surface epithelium and in ovarian cancer.
abstract: Inactivation of the transcription factor and tumor suppressor p53, and overexpression or mutational activation of PIK3CA, which encodes the p110alpha catalytic subunit of phosphatidylinositol-3-kinase (PI3K), are two of the most common deleterious genomic changes in cancer, including in ovarian carcinomas. We investigated molecular mechanisms underlying interactions between these two mediators and their possible roles in ovarian tumorigenesis. We identified two alternate PIK3CA promoters and showed direct binding of and transcriptional inhibition by p53 to one of these promoters. Conditional suppression of functional p53 increased p110alpha transcripts, protein levels and PI3K activity in immortalized, non-tumorigenic ovarian surface epithelial (OSE) cells, the precursors of ovarian carcinoma. Conversely, overexpression of p53 by adenoviral infection and activation of p53 by gamma-irradiation both diminished p110alpha protein levels in normal OSE and ovarian cancer cells. The demonstration that p53 binds directly to the PIK3CA promoter and inhibits its activity identifies a novel mechanism whereby these two mediators regulate cellular functions, and whereby inactivation of p53 and subsequent upregulation of PIK3CA might contribute to the pathophysiology of ovarian cancer.
authors.affiliation: Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada.
authors.forename: Arezoo
authors.initials: A
authors.lastname: Astanehe
authors.forename: David
authors.initials: D
authors.lastname: Arenillas
authors.forename: Wyeth W
authors.initials: WW
authors.lastname: Wasserman
authors.forename: Peter C K
authors.initials: PC
authors.lastname: Leung
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Dunn
authors.forename: Barry R
authors.initials: BR
authors.lastname: Davies
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mills
authors.forename: Nelly
authors.initials: N
authors.lastname: Auersperg
mesh_terms: D002277:Carcinoma / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D058534:Class I Phosphatidylinositol 3-Kinases; D015536:Down-Regulation / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D025461:Feedback, Physiological / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics
chemical_list: D016159:Tumor Suppressor Protein p53; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human