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Cellular effects of CPT‐11 on colon carcinoma cells: Dependence on p53 and hMLH1 status
Author(s) -
Magrini Roberta,
Bhonde Mandar R.,
Hanski MarieLuise,
Notter Michael,
Scherübl Hans,
Boland C. Richard,
Zeitz Martin,
Hanski Christoph
Publication year - 2002
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.10565
Subject(s) - apoptosis , cell cycle checkpoint , cell culture , cell cycle , poly adp ribose polymerase , cancer research , biology , colorectal cancer , dna fragmentation , dna damage , fragmentation (computing) , microbiology and biotechnology , programmed cell death , chemistry , polymerase , dna , cancer , genetics , ecology
Irinotecan (CPT‐11), a recently introduced component of a standard chemotherapy for colorectal cancer, induces in colon cancer cell lines in vitro cell cycle arrest and apoptosis. Since sporadic colon carcinomas exhibit in 50–60% mutations in the p53 gene and in 10–15% an MSI phenotype due in the great majority of the cases to hMLH1 inactivation, we investigated how these lesions influence the cellular effects of CPT‐11 by using colorectal carcinoma cell line HCT116 (which has the genotype p53 +/+ ,hMLH1 − ) and 2 derivative cell lines with the genotypes p53 +/+ ,hMLH1 + and p53 −/− ,hMLH1 − . CPT‐11 treatment induced G2/M arrest in all 3 cell lines within 48 hr. In the p53 +/+ ,hMLH1 + cell line, G2/M arrest was maintained for at least 12 days. There was little concomitant apoptosis, but this was enhanced when the hMLH1 protein was absent. This enhanced apoptosis was accompanied by a shorter duration of the G2/M arrest than in the hMLH1 + cell line. Partial abrogation of G2/M arrest by caffeine enhanced apoptosis in both hMLH1 + and hMLH1 − cells. By contrast, in the p53 −/− cell line, the G2/M arrest was terminated within 4 days. Termination of the G2/M arrest was accompanied by a high level of apoptosis detectable through poly(ADP‐ribose)polymerase (PARP) cleavage, DNA fragmentation and by the appearance of cells with a DNA content <2N. The triggering of G2/M arrest was accompanied in the 3 cell lines by a transient phosphorylation of cdc‐2, while the maintenance of the arrest in the p53 +/+ cell lines was accompanied by the overexpression of p53 and p21 proteins and, consequently, by the inhibition of cdc‐2 kinase activity. These data indicate that: (i) CPT‐11 induces long‐term arrest in p53 +/+ cells and a short‐term arrest followed by apoptosis in p53 −/− cells; (ii) triggering of the arrest is p53 independent and is associated with a brief increase of phosphorylation of cdc‐2, while the p53‐dependent maintenance of G2/M arrest is associated with the inhibition of cdc‐2 kinase activity by p21; and (iii) lack of hMLH1 protein enhances CPT‐11‐induced apoptosis. These results may be useful for designing rational therapies dependent on the p53 and mismatch‐repair status in the tumor. © 2002 Wiley‐Liss, Inc.