[Show abstract][Hide abstract] ABSTRACT: N-Acetyltransferases (NATs) and sulfotransferases (SULTs) are key phase II metabolizing enzymes that can be involved both in the detoxification and in the activation of many human promutagens and procarcinogens.
We investigated the expression of NATs and SULTs in human prostate and tested their role in the activation the N-hydroxy (N-OH) metabolite of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a dietary carcinogen, to form DNA adducts. Western blotting showed detectable levels of NAT1, SULT1A1 and SULT1A3 with marked inter-individual variation. NAT2 and other SULT enzymes were not detectable. NAT1 was localized by immunohistochemistry to the cytoplasm of epithelial cells. The presence of acetyl Co-enzyme A (acetyl CoA) and 3'-phosphoadenosine-5'-phosphosulfate (PAPS), NAT and SULT cofactors, respectively, significantly increased the level of DNA adducts, detected by P-postlabelling analysis, in calf thymus DNA incubated with N-OH-IQ and prostate cytosolic fractions. The enhancement in the level of DNA adducts in the presence of PAPS correlated with the level of SULT1A1 protein. A single prostate cytosol with the SULT1A1*2/*2 genotype produced less DNA adducts than cytosols with the *1/*2 and *1/*1 genotypes. No significant correlation was observed between NAT1 protein level and the formation of DNA adducts, even in the presence of acetyl CoA.
In conclusion, we demonstrated that NAT1, SULT1A1 and SULT1A3 are present in human prostate and that both enzyme classes significantly contribute to the activation of N-hydroxylated heterocyclic amines to DNA-damaging species in this tissue. Variation in expression levels, in combination with dietary and/or environmental exposure to carcinogens, could be influential in determining individual susceptibility to prostate cancer.
No preview · Article · Jul 2006 · Pharmacogenetics and Genomics
[Show abstract][Hide abstract] ABSTRACT: Dietary heterocyclic amines (HCAs) are carcinogenic in rodent prostate requiring activation by enzymes such as cytochrome P450 (CYP) and N-acetyltransferase (NAT).
We investigated by Western blotting and immunohistochemistry the expression of CYP1A1, CYP1A2, and NAT1 in human prostate and in prostate epithelial cells (PECs) derived from primary cultures and tested their ability to activate the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and its N-hydroxy metabolite (N-OH-IQ) to DNA-damaging moieties.
Western blotting identified CYP1A1, CYP1A2, and NAT1. Immunohistochemistry localized NAT1 to the cytoplasm of PECs. Inter-individual variation was observed in the expression levels of CYP1A1, 1A2, and NAT1 (11, 75, and 35-fold, respectively). PECs expressed CYP1A1 and NAT1 but not CYP1A2. When incubated with IQ or N-OH-IQ, PECs formed DNA adducts indicating their ability to metabolically activate these compounds.
Prostate cells possess the capacity to activate dietary carcinogens. PECs may provide a useful model system to study their role in prostate carcinogenesis.