Carboxylesterases Expressed in Human Colon Tumor Tissue and Their Role in CPT-11 Hydrolysis

Sonal P. Sanghani, Sara K. Quinney, Tyler B. Fredenburg, Zejin Sun, Wilhelmina I. Davis, Daryl J. Murry, Oscar W. Cummings, David E. Seitz, William F. Bosron

Research output: Contribution to journalArticlepeer-review

102 Scopus citations


Purpose: The purpose is to develop new analytical methods to study the expression profile of CPT-11 carboxylesterases and topoisomerase I in colon tumor samples and understand the impact of their expression on CPT-11 metabolism in chemotherapy. Experimental Design: We investigated 24 colon tumors for expression of carboxylesterases CES1A1, CES2, CES3, hBr-3, and topoisomerase I genes by real-time PCR and correlated the gene expression with activity assays. The relative abundance of the carboxylesterase isoenzymes and topoisomerase I genes was determined by real-time PCR. Activity assays performed on colon tumor extracts included CPT-11 hydrolase, 4-methylumbelliferyl acetate hydrolase, and topoisomerase I activity assays. Additionally, nondenaturing activity gel electrophoresis with activity staining showed the distribution of carboxylesterases. Results: We detect the expression of CES1A1, CES2, and CES3 carboxylesterase genes in human colon tumors. We were unable to detect the hBr-3 (also called hCE-3) in human liver, colon, or brain. We find large interindividual variation, ≥150-fold, for both CES1A1 and CES3 genes, 23-fold for CES2, and 66-fold for topoisomerase I. Only CES2 gene expression correlated with the carboxylesterase activity assays (P < 0.01) with CPT-11 and 4-methylumbelliferyl acetate as substrates. Nondenaturing activity gel electrophoresis showed that CES2 was the most predominant activity. Topoisomerase I gene expression significantly correlated with topoisomerase I activity (P < 0.01) in the colon tumors, but interindividual variation was very high. Conclusions: We conclude that CES2 is the most abundant carboxylesterase in colon tumors that is responsible for CPT-11 hydrolysis. This pilot study reinforces the hypothesis that there is a large interindividual variation in expression of carboxylesterases that may contribute to variation in therapeutic outcome and/or toxicity of CPT-11 therapy for colon cancer.

Original languageEnglish (US)
Pages (from-to)4983-4991
Number of pages9
JournalClinical Cancer Research
Issue number13
StatePublished - Oct 15 2003
Externally publishedYes

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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