Large-bowel mucosal biotransformation activity in persons at high risk for colorectal cancer. A preliminary report.

The transformation of xenobiotics and endogenous compounds to active carcinogens and their subsequent deactivation as an aid to eradication may be important in the etiology of some gastrointestinal cancers. In mammals the gastrointestinal tract has been shown to be an important site of inducible enzyme systems active in mucosal biotransformation, but few data are available in man. The mucosal activity of CYPIA1 (formerly aryl hydrocarbon hydroxylase), a potential carcinogen-activating enzyme, and catechol-O-methyl transferase, a potential carcinogen-inactivating enzyme were determined in colonic tissue obtained by biopsy. There were no significant differences in activity rates in normal mucosa between colorectal cancer and healthy persons, but significant differences are seen in patients with a history of neoplasia with no evidence of recurrence. The levels of activity of these carcinogen-inductive and -protective enzymes may be prognostic markers, in that the balance or imbalance could play a role in the recurrence of neoplasia. This will require confirmation and prospective studies.