Irinotecan activation by human carboxylesterases in colorectal adenocarcinoma cells

Clin Cancer Res. 2002 Aug;8(8):2696-700.


Carboxylesterases play a critical role in the bioactivation of the anticancer prodrug irinotecan [7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothecin; CPT-11] into its active metabolite SN-38 (ethyl-10-hydroxy-camptothecin). We reported recently that human carboxylesterase-2 (hCE-2) is a higher-affinity, higher-velocity enzyme for irinotecan hydrolysis when compared with hCE-1. To further investigate the role of these isoforms, we cloned both cDNAs into the human colorectal adenocarcinoma cell line HT29. Extracts of HT29 cells transfected with hCE-2 exhibited significantly higher irinotecan hydrolysis (5.2 pmol/mg protein/hr) than hCE-1 (1.0 pmol/mg protein/hr). HT29 cells over-expressing hCE-2 were more sensitive to the toxic effects of irinotecan than cells expressing hCE-1 (EC50 = 0.3 micro M and 6.8 micro M, respectively). Our data further support the notion that hCE-2 plays a substantial role in irinotecan activation in human tissue at relevant pharmacologic concentrations.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacology
  • Blotting, Western
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology*
  • Carboxylic Ester Hydrolases / chemistry
  • Carboxylic Ester Hydrolases / genetics
  • Carboxylic Ester Hydrolases / metabolism*
  • Cloning, Molecular
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / metabolism*
  • DNA, Complementary / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Inhibitors / pharmacology
  • Gene Library
  • Humans
  • Hydrolysis
  • Irinotecan
  • Isoelectric Focusing
  • Kinetics
  • Protein Isoforms
  • Time Factors
  • Transfection
  • Tumor Cells, Cultured


  • Antineoplastic Agents, Phytogenic
  • DNA, Complementary
  • Enzyme Inhibitors
  • Protein Isoforms
  • Irinotecan
  • Carboxylic Ester Hydrolases
  • Camptothecin