Characterization of UDP-glucuronosyltransferase 2A1 (UGT2A1) variants and their potential role in tobacco carcinogenesis

Pharmacogenet Genomics. 2011 Feb;21(2):55-65. doi: 10.1097/FPC.0b013e328341db05.

Abstract

Objective: To examine UGT2A1 expression in human tissues, determine its glucuronidation activity against tobacco carcinogens, and assess the potential functional role of UGT2A1 missense single nucleotide polymorphisms on UGT2A1 enzyme activity.

Methods: Reverse transcription polymerase chain reaction and real time polymerase chain reaction were used to assess UGT2A1 gene expression in various human tissues. A glucuronidation assay measured by reverse phase ultra-performance liquid chromatography was used to determine UGT2A1 activity.

Results: UGT2A1 was expressed in aerodigestive tract tissues including trachea, larynx, tonsil, lung, and colon; no expression was observed in breast, whole brain, pancreas, prostate, kidney, liver, or esophagus. UGT2A1 exhibited highest expression in the lung, followed by trachea >tonsil >larynx >colon >olfactory tissue. Cell homogenates prepared from wildtype UGT2A1(75Lys308Gly) overexpressing HEK293 cells showed significant glucuronidation activity against a variety of polycyclic aromatic hydrocarbons including, 1-hydroxy-benzo(a)pyrene, benzo(a)pyrene-7,8-diol, and 5-methylchrysene-1,2-diol. No activity was observed in UGT2A1 overexpressing cell homogenate against substrates that form N-glucuronides, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), nicotine, or N-OH-2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (N-OH PhIP). A significant (P<0.05) decrease (approximately 25%) in glucuronidation activity (Vmax/KM) was observed against all polycyclic aromatic hydrocarbons substrates for the UGT2A1(75Lys308Gly) variant compared with homogenates from wildtype UGT2A1(75Lys308Gly); no activity was observed for cell homogenates overexpressing the UGT2A1 variant for all substrates tested.

Conclusion: These data suggest that UGT2A1 is an important detoxification enzyme in the metabolism of polycyclic aromatic hydrocarbons within target tissues for tobacco carcinogens and functional polymorphisms in UGT2A1 may play a role in tobacco-related cancer risk.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Blotting, Western
  • Carcinogens / metabolism
  • Chromatography, Liquid
  • Conserved Sequence / genetics
  • Gene Expression Profiling
  • Gene Expression Regulation, Enzymologic
  • Glucuronides / metabolism
  • Glucuronosyltransferase / chemistry
  • Glucuronosyltransferase / genetics*
  • Glucuronosyltransferase / metabolism
  • Glycosylation
  • HEK293 Cells
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Organ Specificity / genetics
  • Polycyclic Aromatic Hydrocarbons / metabolism
  • Polymorphism, Single Nucleotide / genetics*
  • Precancerous Conditions / enzymology*
  • Precancerous Conditions / genetics*
  • Substrate Specificity
  • Tobacco / adverse effects*

Substances

  • Carcinogens
  • Glucuronides
  • Polycyclic Aromatic Hydrocarbons
  • Glucuronosyltransferase