title: Cancer-derived p53 mutants suppress p53-target gene expression--potential mechanism for gain of function of mutant p53.
abstract: Tumour-derived p53 mutants are thought to have acquired 'gain-of-function' properties that contribute to oncogenicity. We have tested the hypothesis that p53 mutants suppress p53-target gene expression, leading to enhanced cellular growth. Silencing of mutant p53 expression in several human cell lines was found to lead to the upregulation of wild-type p53-target genes such as p21, gadd45, PERP and PTEN. The expression of these genes was also suppressed in H1299-based isogenic cell lines expressing various hot-spot p53 mutants, and silencing of mutant p53, but not TAp73, abrogated the suppression. Consistently, these hot-spot p53 mutants were able to suppress a variety of p53-target gene promoters. Analysis using the proto-type p21 promoter construct indicated that the p53-binding sites are dispensable for mutant p53-mediated suppression. However, treatment with the histone deacetylase inhibitor trichostatin-A resulted in relief of mutant p53-mediated suppression, suggesting that mutant p53 may induce hypo-acetylation of target gene promoters leading to the suppressive effects. Finally, we show that stable down-regulation of mutant p53 expression resulted in reduced cellular colony growth in human cancer cells, which was found to be due to the induction of apoptosis. Together, the results demonstrate another mechanism through which p53 mutants could promote cellular growth.
authors.affiliation: Laboratory of Molecular Carcinogenesis, National Cancer Centre, Singapore 169610, Singapore.
authors.forename: Faina
authors.initials: F
authors.lastname: Vikhanskaya
authors.forename: Ming Kei
authors.initials: MK
authors.lastname: Lee
authors.forename: Marco
authors.initials: M
authors.lastname: Mazzoletti
authors.forename: Massimo
authors.initials: M
authors.lastname: Broggini
authors.forename: Kanaga
authors.initials: K
authors.lastname: Sabapathy
mesh_terms: D017209:Apoptosis; D001665:Binding Sites; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D009154:Mutation; D009369:Neoplasms / Q000235:genetics*; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D016159:Tumor Suppressor Protein p53; C012589:trichostatin A