Cellular effects of CPT-11 on colon carcinoma cells: dependence on p53 and hMLH1 status

Int J Cancer. 2002 Sep 1;101(1):23-31. doi: 10.1002/ijc.10565.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis / drug effects*
  • Blotting, Western
  • CDC2 Protein Kinase / metabolism
  • Caffeine / pharmacology
  • Camptothecin / analogs & derivatives
  • Camptothecin / pharmacology*
  • Carrier Proteins
  • Cell Cycle / drug effects
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / pathology*
  • Drug Resistance, Neoplasm
  • Flow Cytometry
  • Gene Deletion
  • Humans
  • Irinotecan
  • MutL Protein Homolog 1
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Nuclear Proteins
  • Phosphorylation / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Time Factors
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • MLH1 protein, human
  • Neoplasm Proteins
  • Nuclear Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Suppressor Protein p53
  • Caffeine
  • Irinotecan
  • CDC2 Protein Kinase
  • MutL Protein Homolog 1
  • Camptothecin