Short Communication Expression of UGT1A and UGT2B mRNA in Human Normal Tissues and Various Cell Lines

UDP-glucuronosyltransferases (UGTs) are major phase II drug metabolism enzymes that catalyze the glucuronidation of numerous endogenous and exogenous compounds. UGTs are divided into two families, UGT1 and UGT2, based on evolutionary divergence and homology. Nine UGT1A and seven UGT2B functional isoforms have been identified in humans. Glucuronidation occurs mainly in liver but also in various extrahepatic tissues, possibly affecting the pharmacokinetics. In the present study, we comprehensively determined the expression of all functional UGT1A and UGT2B isoforms in normal human tissues including liver, lung, stomach, small intestine, colon, kidney, bladder, adrenal gland, breast, ovary, uterus, and testis by semiquantitative reverse transcription-polymerase chain reaction. In addition, the expressions of these UGTs mRNA in 15 kinds of human tissue-derived cell lines were also analyzed. Many UGT isoforms were abundantly expressed in the liver, gastrointestinal tract, and kidney, supporting previous studies. Interestingly, we found that all UGTs except UGT2B17 were expressed in bladder. In steroidrelated tissues, UGTs were expressed in tissueand isoform-specific manners. Expression profiles in human tissue-derived cell lines were not necessarily consistent with those in corresponding normal tissues. Different expression profiles were observed in distinct cell lines derived from the same organ. The information presented here will be helpful for understanding the glucuronidation in various tissues and for choosing appropriate cell lines for in vitro studies. UDP-glucuronosyltransferases (UGTs) are major phase II drug metabolism enzymes in humans (Tukey and Strassburg, 2000). UGTs catalyze the glucuronidation of numerous endogenous compounds such as bilirubin, bile acids, thyroid hormone, and steroid hormones as well as substantial exogenous substrates including therapeutic drugs, carcinogens, and environmental pollutants. Currently, 19 UGT proteins have been identified in humans, and they are divided into three subfamilies, UGT1A, UGT2A, and UGT2B, based on evolutionary divergence and homology (Mackenzie et al., 2005). The human UGT1A gene cluster located on chromosome 2q37 contains multiple unique first exons for each UGT1A and common exons 2 to 5 (Ritter et al., 1992), encoding nine kinds of the functional UGT1A subfamily. The UGT2A and UGT2B genes are located on chromosome 4q13, encoding three and seven functional proteins, respectively. The UGT2A1 and UGT2A2 are formed by differential splicing of variable first exons and common exons 2 to 6, likely the UGT1A gene. Meanwhile, UGT2A3 and each UGT2B are encoded by individual genes. Until now, the clinical significance of UGT2A protein remains to be clarified. In contrast, it is well known that UGT1A and UGT2B play important roles in the glucuronidation of a variety of endogenous and exogenous compounds. The liver plays a central role in metabolism, including glucuronidation. Additionally, extrahepatic tissues such as the gastrointestinal tract and kidney also have a role in metabolism (Soars et al., 2002). The distribution of UGT expression in human tissues has been studied mainly in the liver and gastrointestinal tract (Strassburg et al., 2000; Tukey and Strassburg, 2000). In contrast, the expression in other extrahepatic tissues has not been fully studied. Human tissue-derived cell lines are used as a tool for in vitro drug metabolism studies or induction studies. Hepatoma HepG2 cells and adenocarcinoma Caco-2 cells are frequently used, and the expression of selected UGT isoforms in these cell lines has been reported. However, no study determined the expression of all UGT isoforms in the cell lines. Furthermore, information concerning UGT expression in other cell lines is limited. In the present study, we comprehensively determined the expression of all human UGT isoforms in various normal tissues and human tissue-derived cell lines. Materials and Methods Cell Lines and Culture Condition. HepG2 (hepatocellular carcinoma), Caco-2 (colorectal adenocarcinoma), LS180 (colorectal adenocarcinoma), HEK293 (embryonic kidney), ACHN (renal cell adenocarcinoma), HK-2 (renal proximal tubule cell), SW13 (adrenocortical adenocarcinoma), H295R (adrenocortical adenocarcinoma), MDA-MB-435 (breast ductal carcinoma), and MCF-7 (breast epithelial adenocarcinoma) cells were obtained from American Type Culture Collection (Manassas, VA). HuH7 (hepatocellular carcinoma), HeLa (adenocarcinoma of the cervix of uterus), and OMC-3 (ovarian mucinous cystadenocarcinoma) cells were obtained from RIKEN BioResource Center (Ibaraki, Japan). HLE cells (hepatocellular carcinoma) were obtained from the Japan Collection of Research Biosources (Tokyo, Japan). Ishikawa (endometrial adenocarcinoma) cells were generous gifts from Dr. Masato Nishida, Tsukuba University (Ibaraki, Japan). HLE, HuH7, SW13, MDA-MB-435, HeLa, and Ishikawa cells were cultured in DMEM (Nissui Pharmaceutical, Tokyo, Japan) supplemented with 10% fetal bovine serum (FBS) (Invitrogen, Carlsbad, CA). HepG2, Caco-2, LS180, ACHN, and MCF-7 cells were cultured in DMEM supplemented with Article, publication date, and citation information can be found at http://dmd.aspetjournals.org. doi:10.1124/dmd.108.021428. □S The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material. ABBREVIATIONS: UGT, UDP-glucuronosyltransferase; DMEM, Dulbecco’s modified Eagle’s medium; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; RT-PCR, reverse transcriptase-polymerase chain reaction. 0090-9556/08/3608-1461–1464$20.00 DRUG METABOLISM AND DISPOSITION Vol. 36, No. 8 Copyright © 2008 by The American Society for Pharmacology and Experimental Therapeutics 21428/3364142 DMD 36:1461–1464, 2008 Printed in U.S.A. 1461 http://dmd.aspetjournals.org/content/suppl/2008/05/14/dmd.108.021428.DC1 Supplemental material to this article can be found at: at A PE T Jornals on A ril 4, 2017 dm d.aspurnals.org D ow nladed from