Variation in enzymes of arylamine procarcinogen biotransformation among bladder cancer patients and control subjects

Arylamines such as 2-naphthylamine and 4-aminobiphenyl are suspected human bladder procarcinogens that require bioactivation to DNA-reactive species t o exert their carcinogenic potential. The goals of the present study were ( i) to assay for the presence of the arylamine acetyltransferases NAT1 and N AT2, and of the cytochrome P450 isoform CYP1A2, in human bladder epithelium ; and (ii) to determine whether the activities of these arylamine biotransf orming enzymes differ between bladder cancer patients and control subjects. We measured in-vitro enzyme activities in biopsies of normal, undiseased b ladder epithelium obtained from 103 bladder cancer patients. NAT1 activity was detectable in all samples, with mean levels higher than those found in human liver. Kinetic evidence also suggested low levels of NAT2 expression in this tissue, but there was no detectable CYP1A2 by either enzymatic or i mmunochemical measurements. We also compared several probe drug indices of in-vivo NAT1, NAT2 and CYP1A2 activity between 53 bladder cancer patients a nd 96 cancer-free control subjects who were carefully matched for age, gend er and smoking status, NAT1 and NAT2 genotypes were also determined. No sig nificant differences were found between bladder cancer patients and control subjects for a number of individual phenotypic or genotypic predictors of enzyme function. Our results suggest that although expression of particular arylamine biotransforming enzymes within the bladder tissue could play a s ignificant role in locally bioactivating arylamine procarcinogens in theory , interindividual variations in CYP1A2, NAT1 and NATL activities do not sig nificantly differ between bladder cancer patients and control subjects when potential arylamine exposures are controlled for in the experimental study design. Pharmacogenetics 11:7-20 (C) 2001 Lippincott Williams & Wilkins.