title: Enhanced sensitivity to cis-diamminedichloroplatinum(II) of a human carcinoma cell line with mutated p53 gene by cyclin-dependent kinase inhibitor p21(WAF1) expression.
abstract: p53-mediated induction of p21(WAF1), a cyclin-dependent protein kinase inhibitor, is known to protect cancer cells from the cytotoxic effects of anti-cancer drugs or gamma-irradiation. Since the p53 gene is frequently inactivated in cancer cells, we examined whether p21(WAF1) expression may alter the sensitivity of cancer cells with mutated p53 gene to anti-cancer drugs. Cells of a colon cancer cell line DLD-1 were transfected with p21(WAF1) expression vector controlled by a tetracycline-repressable promoter and transfectants were cloned (Dp21-1). p21(WAF1) expression induced by removal of tetracycline from culture media repressed cell proliferation and resulted in altered cell shape, suggesting induction of differentiation. Dp21-1 cells with p21(WAF1) expression were more sensitive to cis-diamminedichloroplatinum(II) (CDDP) (IC(50) value, 10 microM) than those without p21(WAF1) expression (IC(50), 22 microM). Sensitivity to doxorubicin was not different between Dp21-1 cells with and without p21(WAF1) expression. DNA ladder formation was observed in Dp21-1 cells treated with CDDP, indicating that the enhanced sensitivity to CDDP involves apoptosis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cytosolic protein revealed that subunit protein bands with M(r) 55 kDa and 44 kDa were markedly increased in cells with p21(WAF1) expression. By immunoblotting, these proteins were identified as c-Jun N-terminal kinase (JNK) 2 and p38 mitogen-activated protein kinase (MAPK) delta, respectively, both of which are believed to be involved in apoptosis induction by CDDP. These results suggest that p21(WAF1) may enhance the sensitivity of colon cancer cells with mutated p53 gene to CDDP, possibly through the JNK and p38 MAPK pathways.
authors.affiliation: Second Department of Biochemistry, Hirosaki University School of Medicine, Hirosaki.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Satou
authors.forename: Syu
authors.initials: S
authors.lastname: Aizawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayakari
authors.forename: Keizou
authors.initials: K
authors.lastname: Ookawa
authors.forename: Shigeki
authors.initials: S
authors.lastname: Tsuchida
mesh_terms: D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000633:toxicity*; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002945:Cisplatin / Q000633:toxicity*; D003110:Colonic Neoplasms; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics*; D004317:Doxorubicin / Q000633:toxicity; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016158:Genes, p53; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D010446:Peptide Fragments; D004317:Doxorubicin; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D002945:Cisplatin