title: Role of p21 in apoptosis and senescence of human colon cancer cells treated with camptothecin.
abstract: Treatment of cells with the anti-cancer drug camptothecin (CPT) induces topoisomerase I (Top1)-mediated DNA damage, which in turn affects cell proliferation and survival. In this report, we demonstrate that treatment of the wild-type HCT116 (wt HCT116) human colon cancer cell line and the isogenic p53(-/-) HCT116 and p21(-/-) HCT116 cell lines with a high concentration (250 nm) of CPT resulted in apoptosis, indicating that apoptosis occurred by a p53- and p21-independent mechanism. In contrast, treatment with a low concentration (20 nm) of CPT induced cell cycle arrest and senescence of the wt HCT116 cells, but apoptosis of the p53(-/-) HCT116 and p21(-/-) HCT116 cells. Further investigations indicated that p53-dependent expression of p21 blocked apoptosis of wt HCT116 cells treated with 20 nm, but not 250 nm CPT. Interestingly, blocking of the apoptotic pathway, by Z-VAD-FMK, in p21(-/-) HCT116 cells following treatment with 20 nm CPT did not permit the cells to develop properties of senescence. These observations demonstrated that p21 was required for senescence development of HCT116 cells following treatment with low concentrations of CPT.
authors.affiliation: Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA. zhiyong_han@brown.edu
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Han
authors.forename: Wenyi
authors.initials: W
authors.lastname: Wei
authors.forename: Stephen
authors.initials: S
authors.lastname: Dunaway
authors.forename: James W
authors.initials: JW
authors.lastname: Darnowski
authors.forename: Paul
authors.initials: P
authors.lastname: Calabresi
authors.forename: John
authors.initials: J
authors.lastname: Sedivy
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hendrickson
authors.forename: Kannan V
authors.initials: KV
authors.lastname: Balan
authors.forename: Panayotis
authors.initials: P
authors.lastname: Pantazis
authors.forename: James H
authors.initials: JH
authors.lastname: Wyche
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology*; D002453:Cell Cycle; D016922:Cellular Senescence; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics* / Q000502:physiology*; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011485:Protein Binding; D013997:Time Factors; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53; D001616:beta-Galactosidase; D001973:Bromodeoxyuridine; D002166:Camptothecin