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Published on: July 29, 2010
Xenobiotic metabolising enzyme expression in colonic neoplasia
J A McKay1, G I Murray, R J Weaver
1Department of Pathology, University of Aberdeen.
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.
Insights
Cytochrome P450 1A and 3A are more specific markers for colon neoplasia than other enzymes. These enzymes, crucial for metabolizing carcinogens and drugs, show distinct expression patterns in normal colon versus tumors.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Cytochrome P450, epoxide hydrolase, and glutathione S-transferase enzymes are vital for metabolizing carcinogens and anti-cancer drugs.
- Understanding their expression in the colon is crucial for cancer research.
Purpose of the Study:
- To investigate the expression and cellular distribution of specific xenobiotic metabolizing enzymes in normal colon, adenomas, and adenocarcinoma.
- To determine if these enzymes can serve as specific markers for colonic neoplasia.
Main Methods:
- Immunohistochemistry was used to study the expression of cytochrome P450 (1A and 3A), epoxide hydrolase, and glutathione S-transferase (alpha, mu, pi) forms.
- Enzyme localization was analyzed in normal colon tissue, colonic adenomas, and colon adenocarcinoma samples.
Main Results:
- All studied enzymes were primarily expressed in epithelial cells, with exceptions for cytochrome P450 3A (mast cells) and glutathione S-transferase pi (inflammatory cells).
- Cytochrome P450 1A and 3A showed significantly higher and more specific expression in adenomas and carcinomas compared to normal colon.
- Epoxide hydrolase and glutathione S-transferase mu/alpha/pi showed broader expression in normal colon tissue.
Conclusions:
- Cytochrome P450 1A and cytochrome P450 3A are more specific biomarkers for colonic neoplasia than epoxide hydrolase or glutathione S-transferases.
- These findings aid in understanding colon cancer development and identifying potential diagnostic markers.
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