title: p53-Independent expression of wild-type p53-induced phosphatase 1 (Wip1) in methylmethane sulfonate-treated cancer cell lines and human tumors.
abstract: Wild-type p53-induced phosphatase 1 (Wip1, PPM1D) is induced by p53 in response to various stressors and dephosphorylates cellular target proteins involved in DNA repair and cell cycle checkpoint pathways. The Wip1 gene is frequently amplified or overexpressed in human cancers, promoting tumor growth by switching off major checkpoint kinases and p53. To explore wild-type p53-independent Wip1 induction, Wip1 promoter activity and its transcript level were evaluated by luciferase assay and real-time PCR, after methylmethane sulfonate (MMS) treatment in breast cancer cell lines and p53-null cell lines. Wip1 promoter activities in response to UV irradiation and various anti-cancer agents were compared between wild-type and a p53-response element (p53RE) mutated construct. Wip1 expression and its effects were examined in primary non-small cell lung cancer (NSCLC) and colon tumor cells by using Wip1-specific siRNA. MMS induced Wip1 promoter activity in Hs578T, MDA-MB-231, and SK-BR-3 cells expressing DNA binding-deficient p53 mutants. A549-E6 and HCT116 (p53(-/-)) cells retained substantial Wip1 induction. Wip1 promoter activity was reduced, but not eliminated, in cells expressing a promoter containing a mutated p53-response element. Wip1 induction was not blocked by SB202190 or SP600125. MMS increased Wip1 expression in primary non-small cell lung cancer cells expressing a p53 R175H mutant. Our data indicate that Wip1 is induced in the absence of functional p53, like p38 MAPK and JNK, as a stress response terminator.
authors.affiliation: Department of Pathology, University of Ulsan College of Medicine, Asan Medical center, Seoul, Republic of Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Park
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Song
authors.forename: Hyun Mi
authors.initials: HM
authors.lastname: Kim
authors.forename: Hye-Sook
authors.initials: HS
authors.lastname: Han
authors.forename: Hyang Sook
authors.initials: HS
authors.lastname: Seol
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Jang
authors.forename: Jene
authors.initials: J
authors.lastname: Choi
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D017931:DNA Primers; D020868:Gene Silencing; D006801:Humans; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D009369:Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D000071636:Protein Phosphatase 2C; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D016159:Tumor Suppressor Protein p53; D008741:Methyl Methanesulfonate; C000607458:PPM1D protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C