title: p53 protein regulates the effects of amifostine on apoptosis, cell cycle progression, and cytoprotection.
abstract: To determine the role of p53 protein on the cellular effects of amifostine, we used molecularly engineered HCT116 colon cancer cells in which the p53 gene was inactivated by targeted homologous recombination or p53 protein was degraded by high-level expression of papillomavirus E6 protein. Amifostine induced a G1 arrest and protected against paclitaxel toxicity in p53-proficient but not in p53-deficient cells. In the absence of p53 protein, amifostine enhanced the cytotoxicity of paclitaxel. In addition, treatment of HCT116 cells with amifostine alone resulted in apoptotic cell death. Compared with p53-deficient cells, p53-proficient cells exhibited low-level resistance to amifostine-induced apoptosis. Amifostine induced the expression of p53 protein in p53-proficient cells and the expression of p21 protein in both p53-proficient and -deficient cells. These findings indicate that amifostine-induced G1 arrest and cytoprotection are mediated via a pathway that is dependent on p53 protein and that amifostine-induced expression of p21 protein is not sufficient to sustain a G1 arrest or to mediate cytoprotection. In addition, these findings identify p53 protein as a mechanism of resistance to amifostine-induced apoptosis.British
authors.affiliation: Department of Medicine and Cancer Center, University of California San Diego, La Jolla 92093, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Gerhold
authors.forename: M W
authors.initials: MW
authors.lastname: Palmer
authors.forename: R D
authors.initials: RD
authors.lastname: Christen
mesh_terms: D004999:Amifostine / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D019610:Cytoprotection; D006801:Humans; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53; D004999:Amifostine