title: Xenobiotic metabolising enzyme expression in colonic neoplasia.
abstract: The cytochrome P450, epoxide hydrolase, and glutathione S-transferase enzyme families play an important part in the metabolism of many carcinogens and anti-cancer drugs. The expression of two forms of cytochrome P450 (P450 1A and P450 3A), epoxide hydrolase and of the alpha, mu, and pi forms of glutathione S-transferase in normal colon, colonic adenomas, and adenocarcinoma of the colon were studied by immunohistochemistry. This allowed the precise cellular site and distribution of each enzyme to be determined. Expression of all the xenobiotic metabolising enzymes studied was almost wholly confined to the epithelial cells, whether in normal, adenoma or carcinoma samples, except that cytochrome P450 3A was also identified in mast cells and glutathione S-transferase pi was also present in chronic inflammatory cells. Cytochrome P450 was present in only a small proportion of normal colon samples, whereas epoxide hydrolase and glutathione S-transferase mu were identified in about half, and glutathione S-transferase alpha and pi in most normal samples. By contrast all the enzyme forms studied were expressed in virtually all adenomas and in over half the carcinomas. These results suggest that cytochrome P450 1A and cytochrome P450 3A are more specific markers of colonic neoplasia than epoxide hydrolase or glutathione S-transferases alpha, mu, and pi.
authors.affiliation: Department of Pathology, University of Aberdeen.
authors.forename: J A
authors.initials: JA
authors.lastname: McKay
authors.forename: G I
authors.initials: GI
authors.lastname: Murray
authors.forename: R J
authors.initials: RJ
authors.lastname: Weaver
authors.forename: S W
authors.initials: SW
authors.lastname: Ewen
authors.forename: W T
authors.initials: WT
authors.lastname: Melvin
authors.forename: M D
authors.initials: MD
authors.lastname: Burke
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology*; D000236:Adenoma / Q000201:enzymology*; D001189:Aryl Hydrocarbon Hydroxylases; D014408:Biomarkers, Tumor / Q000032:analysis*; D003106:Colon / Q000201:enzymology; D003110:Colonic Neoplasms / Q000201:enzymology*; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D004851:Epoxide Hydrolases / Q000032:analysis*; D005982:Glutathione Transferase / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes; D010088:Oxidoreductases / Q000032:analysis*; D010089:Oxidoreductases, N-Demethylating / Q000032:analysis*; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D007527:Isoenzymes; D015262:Xenobiotics; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A; D010089:Oxidoreductases, N-Demethylating; D005982:Glutathione Transferase; D004851:Epoxide Hydrolases