Abstract

The UDP-glucuronosyltransferase (UGT) 2B subfamily of enzymes plays an important role in the metabolism of numerous endogenous and exogenous compounds, including various carcinogens present in tobacco smoke. The goal of the present study was to examine the levels of expression of individual UGT2B genes in various tissues that are targets for tobacco carcinogenesis. Using MT-ATP6 as the experimentally validated housekeeping gene, the highest extrahepatic expression of UGT2B genes was observed in human tonsil, with UGT2B expression levels similar to that observed in human liver. UGT2B17 exhibited high relative expression in most tissues examined, including lung, most tissues of the aerodigestive tract, and pancreas. UGT2B7 expression was highest in pancreas but low or undetectable in most other tissues examined. UGT2B10 expression was high in both tonsil and tongue. There was wide variability between individuals in the magnitude of expression in each tissue site, and there were strong correlations between UGT2B expression levels in different individuals within many of the tissue sites, suggesting coordinated regulation of UGT2B gene expression in extrahepatic tissues. In the liver, UGTs 2B4, 2B7, 2B10, and 2B15 were significantly correlated with each other (all r² > 0.70, P < 0.0001). In all examined tissues of the aerodigestive tract, UGTs 2B10, 2B11, and 2B17 exhibited a strong correlation with each other (all r² > 0.75, P < 0.05). UGTs 2B7 and 2B10 exhibited a strong inverse correlation in the pancreas (r² = –0.95, P < 0.01). These data suggest that specific UGT2B enzymes important in tobacco carcinogen metabolism are expressed and coordinately regulated in various target sites for tobacco-related cancers.