title: Repair Defect in p21 WAF1/CIP1 -/- human cancer cells.
abstract: p53 induction and cell cycle arrest occur following DNA damage, possibly to allow repair prior to replication. p21WAF1/CIP1, a cyclin-cyclin-dependent kinase inhibitor and proliferating cell nuclear antigen-interacting protein, is induced by p53 and mediates the cell cycle arrest. To investigate a role for p21 in DNA repair in vivo, we studied the expression of in vitro damaged reporter DNA transfected into p21 +/+ or -/- HCT116 human colon cancer cells. Introduction of UV-damaged or cisplatinum-damaged cytomegalovirus-driven beta-galactosidase reporter DNA into tumor cells revealed a significant decrease (2-5-fold) in reporter expression in p21 -/- versus +/+ cells. In the absence of DNA damage, there was a significant increase (2-3-fold) in the number of 6-TG-resistant colonies derived from p21 -/- versus +/+ cells. Reintroduction of wild-type p21, but not a p21 C-terminal truncation mutant which lacks the proliferating cell nuclear antigen interaction domain, stimulated (2-3-fold) the repair capacity of the p21-deficient cells. We conclude that p21 deficiency is associated with a defect in DNA repair, which could lead to an increased sensitivity of tumor cells to DNA damage.
authors.affiliation: Howard Hughes Medical Institute, Laboratory of Molecular Oncology and Cell Cycle Regulation, University of Pennsylvania Comprehensive Cancer Center, Philadelphia, 19104, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: McDonald
authors.forename: G S
authors.initials: GS
authors.lastname: Wu
authors.forename: T
authors.initials: T
authors.lastname: Waldman
authors.forename: W S
authors.initials: WS
authors.lastname: El-Deiry
mesh_terms: D002453:Cell Cycle / Q000235:genetics*; D002455:Cell Division; D002945:Cisplatin / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D004261:DNA Replication; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D017930:Genes, Reporter / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D009363:Neoplasm Proteins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D013866:Thioguanine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D014466:Ultraviolet Rays
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D018809:Proliferating Cell Nuclear Antigen; D016159:Tumor Suppressor Protein p53; D013866:Thioguanine; D002945:Cisplatin