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

• Published in: Clinical cancer research Vol. 9; no. 13; pp. 4983 - 4991
• Main Authors: SANGHANI, Sonal P, QUINNEY, Sara K, FREDENBURG, Tyler B, ZEJIN SUN, DAVIS, Wilhelmina I, MURRY, Daryl J, CUMMINGS, Oscar W, SEITZ, David E, BOSRON, William F
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15.10.2003
• Subjects: Antineoplastic agents; Biological and medical sciences; Blotting, Northern; Blotting, Western; Brain - metabolism; Camptothecin - analogs & derivatives; Camptothecin - metabolism; Carboxylesterase - metabolism; Carboxylic Ester Hydrolases - biosynthesis; Carboxylic Ester Hydrolases - metabolism; Cell Line, Tumor; Chemotherapy; Colon - metabolism; Colonic Neoplasms - enzymology; Colonic Neoplasms - metabolism; DNA Topoisomerases, Type I - metabolism; Electrophoresis, Polyacrylamide Gel; Female; Humans; Hydrolases - metabolism; Hydrolysis; Liver - metabolism; Male; Medical sciences; Pharmacology. Drug treatments; Reverse Transcriptase Polymerase Chain Reaction; RNA - metabolism; Umbelliferones - metabolism; Antineoplastic agent; Human; Enzyme; Esterases; Malignant tumor; Carboxylesterase; Gene expression; Metabolism; In vitro; Carboxylic ester hydrolases; Colonic disease; Hydrolysis; Irinotecan; Digestive diseases; Hydrolases; Intestinal disease; Colon; Mechanism of action
• ISSN: 1078-0432; 1557-3265

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.