Mechanisms underlying p53 regulation of PIK3CA transcription in ovarian surface epithelium and in ovarian cancer

Inactivation of the transcription factor and tumor suppressor p53, and overexpression or mutational activation of PIK3CA, which encodes the p110α 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 p110α 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 γ-irradiation both diminished p110α 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.

[1]  P. Friedman,et al.  The p53 protein is an unusually shaped tetramer that binds directly to DNA. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[2]  H. Westphal,et al.  Abnormal structure and expression of the p53 gene in human ovarian carcinoma cell lines. , 1992, Cancer research.

[3]  K. Sobczak,et al.  Structural Determinants of BRCA1 Translational Regulation* , 2002, The Journal of Biological Chemistry.

[4]  D. Pinkel,et al.  Genetic analysis of benign, low-grade, and high-grade ovarian tumors. , 1995, Cancer research.

[5]  P. May,et al.  Twenty years of p53 research: structural and functional aspects of the p53 protein , 1999, Oncogene.

[6]  Chun-Fang Xu,et al.  Mutations and alternative splicing of the BRCA1 gene in UK breast/ovarian cancer families , 1997, Genes, chromosomes & cancer.

[7]  S. Kyo,et al.  Adenoviral expression of p53 represses telomerase activity through down-regulation of human telomerase reverse transcriptase transcription. , 2000, Clinical cancer research : an official journal of the American Association for Cancer Research.

[8]  G. Zambetti,et al.  Wild-type p53 binds to the TATA-binding protein and represses transcription. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[9]  K. Kinzler,et al.  Genetic instabilities in human cancers , 1998, Nature.

[10]  N A Kolchanov,et al.  Eukaryotic mRNAs encoding abundant and scarce proteins are statistically dissimilar in many structural features , 1998, FEBS letters.

[11]  Yong Liao,et al.  HER-2/neu induces p53 ubiquitination via Akt-mediated MDM2 phosphorylation , 2001, Nature Cell Biology.

[12]  G. Mills,et al.  Inhibition of phosphatidylinositol 3'-kinase increases efficacy of paclitaxel in in vitro and in vivo ovarian cancer models. , 2002, Cancer research.

[13]  P. Leung,et al.  Ovarian surface epithelium: biology, endocrinology, and pathology. , 2001, Endocrine reviews.

[14]  Brendan M Leung,et al.  Chemoresistance in human ovarian cancer: the role of apoptotic regulators , 2003, Reproductive biology and endocrinology : RB&E.

[15]  G. Mize,et al.  Role of two upstream open reading frames in the translational control of oncogene mdm2 , 1999, Oncogene.

[16]  P. Leung,et al.  Differentiation and growth potential of human ovarian surface epithelial cells expressing temperature-sensitive SV40 T antigen , 2001, In Vitro Cellular & Developmental Biology - Animal.

[17]  C. Prives,et al.  Functional interaction between p53, the TATA-binding protein (TBP), andTBP-associated factors in vivo , 1996, Molecular and cellular biology.

[18]  Y. Samuels,et al.  Oncogenic mutations of PIK3CA in human cancers. , 2004, Current topics in microbiology and immunology.

[19]  S. Duga,et al.  A new exon in the 5' untranslated region of the connexin32 gene. , 1999, European Journal of Biochemistry.

[20]  G. Mills,et al.  In vivo and in vitro ovarian carcinoma growth inhibition by a phosphatidylinositol 3-kinase inhibitor (LY294002). , 2000, Clinical cancer research : an official journal of the American Association for Cancer Research.

[21]  M. Frommer,et al.  CpG islands in vertebrate genomes. , 1987, Journal of molecular biology.

[22]  M. Barton,et al.  p53-Mediated Repression of Alpha-Fetoprotein Gene Expression by Specific DNA Binding , 1999, Molecular and Cellular Biology.

[23]  Armando Rodriguez.  What is MDM-2?: , 1994 .

[24]  A. Børresen-Dale,et al.  PIK3CA mutations in advanced ovarian carcinomas , 2005, Human mutation.

[25]  B. Davies,et al.  Immortalisation of human ovarian surface epithelium with telomerase and temperature-sensitive SV40 large T antigen. , 2003, Experimental cell research.

[26]  T. Unger,et al.  Critical role for Ser20 of human p53 in the negative regulation of p53 by Mdm2 , 1999, The EMBO journal.

[27]  N. Altorki,et al.  Inhibition of Cyclooxygenase-2 Gene Expression by p53* , 1999, The Journal of Biological Chemistry.

[28]  C. Ingles,et al.  Direct interaction between the transcriptional activation domain of human p53 and the TATA box-binding protein. , 1993, The Journal of biological chemistry.

[29]  Katsuo Suzuki,et al.  Protein synthesis—dependent cytoplasmic translocation of p53 protein after serum stimulation of growth‐arrested MCF‐7 cells , 1993, Molecular carcinogenesis.

[30]  F. Meric,et al.  Translation initiation in cancer: a novel target for therapy. , 2002, Molecular cancer therapeutics.

[31]  Jiandong Chen,et al.  Transcriptional Repression of the Anti-apoptoticsurvivin Gene by Wild Type p53* , 2002, The Journal of Biological Chemistry.

[32]  J. Chou,et al.  Differentiated mammalian cell lines immortalized by temperature-sensitive tumor viruses. , 1989, Molecular endocrinology.

[33]  A. Lash,et al.  Frequent Mutation of the PIK3CA Gene in Ovarian and Breast Cancers , 2005, Clinical Cancer Research.

[34]  K. McLure,et al.  How p53 binds DNA as a tetramer , 1998, The EMBO journal.

[35]  J W Gray,et al.  An approach to analysis of large-scale correlations between genome changes and clinical endpoints in ovarian cancer. , 2000, Cancer research.

[36]  P. Burns,et al.  Increased accumulation of p53 protein in cisplatin‐resistant ovarian cell lines , 1993, International journal of cancer.

[37]  D. Latchman,et al.  p53 Suppresses the Activation of the Bcl-2 Promoter by the Brn-3a POU Family Transcription Factor* , 1999, The Journal of Biological Chemistry.

[38]  Y Taya,et al.  DNA damage‐inducible phosphorylation of p53 at N‐terminal sites including a novel site, Ser20, requires tetramerization , 1999, The EMBO journal.

[39]  Hongbing Wang,et al.  The Human Sulfotransferase SULT1A1 Gene Is Regulated in a Synergistic Manner by Sp1 and GA Binding Protein , 2004, Molecular Pharmacology.

[40]  S. Cregan,et al.  Helper-dependent adenovirus vectors: their use as a gene delivery system to neurons , 2000, Gene Therapy.

[41]  Brendan M Leung,et al.  p53 is a determinant of X-linked inhibitor of apoptosis protein/Akt-mediated chemoresistance in human ovarian cancer cells. , 2003, Cancer research.

[42]  Terrence S. Furey,et al.  The UCSC Genome Browser Database , 2003, Nucleic Acids Res..

[43]  K. Kinzler,et al.  Definition of a consensus binding site for p53 , 1992, Nature Genetics.

[44]  T. Mak,et al.  Regulation of PTEN transcription by p53. , 2001, Molecular cell.

[45]  Arnold J Levine,et al.  p53 regulates cell survival by inhibiting PIK3CA in squamous cell carcinomas. , 2002, Genes & development.

[46]  Y. Sun,et al.  p53 Down-regulates Human Matrix Metalloproteinase-1 (Collagenase-1) Gene Expression* , 1999, The Journal of Biological Chemistry.

[47]  P. Kruk,et al.  Simian virus 40-transformed human ovarian surface epithelial cells escape normal growth controls but retain morphogenetic responses to extracellular matrix. , 1992, American journal of obstetrics and gynecology.

[48]  R. A. Johnson,et al.  Transcriptional Repression by p53 through Direct Binding to a Novel DNA Element* 210 , 2001, The Journal of Biological Chemistry.

[49]  J Gil,et al.  Ovarian dysplasia in epithelial inclusion cysts. A morphometric approach using neural networks , 1995, Cancer.

[50]  L. Mayo,et al.  A phosphatidylinositol 3-kinase/Akt pathway promotes translocation of Mdm2 from the cytoplasm to the nucleus , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[51]  Stephen N. Jones,et al.  Regulation of p53 stability by Mdm2 , 1997, Nature.

[52]  E. Stavridi,et al.  Phosphorylation of Ser-20 mediates stabilization of human p53 in response to DNA damage. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[53]  Joe W. Gray,et al.  PIK3CA is implicated as an oncogene in ovarian cancer , 1999, Nature Genetics.

[54]  P. Giannakakou,et al.  The importance of p53 location: nuclear or cytoplasmic zip code? , 2003, Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy.

[55]  A. Toker,et al.  Signalling through the lipid products of phosphoinositide-3-OH kinase , 1997, Nature.

[56]  F. McCormick,et al.  Phosphoinositide 3-OH Kinase (PI3K) and PKB/Akt Delay the Onset of p53-mediated, Transcriptionally Dependent Apoptosis* , 1999, The Journal of Biological Chemistry.

[57]  A. Levine,et al.  Role of T antigen interactions with p53 in tumorigenesis. , 2001, Seminars in cancer biology.

[58]  O. Elroy-Stein,et al.  Ataxia-telangiectasia: structural diversity of untranslated sequences suggests complex post-transcriptional regulation of ATM gene expression. , 1997, Nucleic acids research.

[59]  G. Chenevix-Trench,et al.  Frequent PTEN/MMAC mutations in endometrioid but not serous or mucinous epithelial ovarian tumors. , 1998, Cancer research.

[60]  J N Weinstein,et al.  Characterization of the p53 tumor suppressor pathway in cell lines of the National Cancer Institute anticancer drug screen and correlations with the growth-inhibitory potency of 123 anticancer agents. , 1997, Cancer research.

[61]  A. Thor,et al.  p53 gene mutations and protein accumulation in human ovarian cancer. , 1993, Proceedings of the National Academy of Sciences of the United States of America.