Anna Radominska-Pandya, Ph.D.

Professor

Ph.D., Institute of Biochemistry and Biophysics,

Polish Academy of Sciences, Warsaw, Poland

Clinical and Pharmacological Roles of Human UDP-Glucuronosyltransferases

Structure-function relationship studies of human UDP-glucuronosyltransferases (UGTs).  Our laboratory is extensively involved in structure-function relationship studies of human UGTs.  UGTs are a class of enzymes that are involved in the detoxification of a variety of toxic and endogenous compounds.  Our goal is to identify critical amino acids within the active sites of these enzymes using photoaffinity labeling and crystallography.  For our studies we have available sufficient amounts of recombinant UGT protein expressed in baculovirus infected Sf9 insect cells.  In our photoaffinity experiments, we use UGT substrates or inhibitors that have been modified with a photolabile group, which upon photoactivation of this probe in situ covalently bind to the active site of the UGT protein.  Our probes have proven indispensable for the identification of both the co-substrate and substrate-binding sites of the UGTs.  We have generated the first comprehensive data in this area, identifying the phenol binding site of UGT1A10.  We also have fruitful collaborative studies that have led to the generation of the first partial crystal structure of any mammalian UGT (human UGT2B7).  Information generated from these studies will lead to the identification of more UGT binding sites and will eventually result in the elucidation of the molecular mechanisms of the important detoxification processes carried out by UGTs.  This information can then be directly applied to pharmacological and clinical settings, resulting in the design of safer and more efficient medications.

The role of UGTs and SULTs in the biotransformation of Coumadin (warfarin).  Recently, we identified hydroxylated derivatives of warfarin as novel substrates for human hepatic and extrahepatic UGTs (UGT1A1, -1A3, -1A8, -1A9, and -1A10) and SULTs (SULT1A1, -1A3, -1B1, and -1E1).  Using metabolomics, we have also investigated the in vivo formation of glucuronidated and sulfated hydroxywarfarins in patients on warfarin therapy.  These studies have clearly validated a role for the use of conjugated warfarin metabolites as novel biomarkers for the development of personalized warfarin therapy and have demonstrated a direct correlation between the in vivo and in vitro capacity to generate conjugated warfarin metabolites.

Regulation of Human UGTs.  Our research in this area is focused on the transcriptional regulation of UGTs from the UGT1A and UGT2B families.  Our research builds on our findings that: 1) UGT1A isoforms are target genes for two human nuclear receptors, hPXR and hCAR. 2) UGT2B7, which glucuronidates a variety of endogenous compounds recognized as ligands for NRs, is down-regulated by bile acids and retinoic acid.  3) Two human isoforms from the UGT1A family, UGT1A3 and 1A4, are targets for AhR.  Characterization of the mechanism by which endogenous and exogenous compounds regulate UGT expression can lead to: 1) understanding of UGTs function in a normal state and in various diseases, such as cancer, and 2) it will also allow for the development of NR-targeted genes that will be able to increase or decrease UGTs activity.

Suppression of human UGTs in cancer cells.   It is recognized that UGTs can metabolize a wide range of toxins and carcinogens and, therefore, play a critical role in detoxification of these compounds.  We and others have observed a correlation between the absence of UGT expression and cell proliferation. Comparisons of UGT expression levels in normal and cancer cells demonstrated a significant reduction in UGT mRNA in a number of tumor samples.  It is hypothesized that down regulation of UGTs could be one of the basic events in neoplastic transformation.  We have demonstrated that the levels of UGTs in cancer cells, as compared to corresponding normal cells, are significantly reduced or totally absent. Our study with ovarian cancer cells, which are lacking UGT2B7, demonstrated that stable expression of UGT2B7 in these cells resulted in colony formation, cell growth arrest, and decreased cell proliferation.  Similar studies are also being done with breast cancer tissue.  These data allows us to propose a role for UGTs in preventing hormone-induced and/or chemical carcinogenesis. 

Selected Publications

Miller GP, Jones DR, Sullivan SZ, Mazur A, Owen SN, Mitchell NC, Radominska-Pandya A, Moran JH. (2009) Assessing cytochrome P450 and UDP-glucuronosyltransferase contributions to warfarin metabolism in humans.  Chem Res Toxicol 22, 1239-45.  [Abstract]

Starlard-Davenport A, Lyn-Cook B, Radominska-Pandya A. (2008) Identification of UDP-glucuronosyltransferase 1A10 in non-malignant and malignant human breast tissue.  Steroids 73, 611-620.  [Abstract]

Zielinska A, Lichti CF, Bratton SM, Mitchell NC, Gallus-Zawada A, Le VH, Finel M, Radominska-Pandya A, Moran JH.  Glucuronidation of monohydroxylated warfarin metabolites by human liver microsomes and human recombinant UDP-glucuronosyltransferases. (2008) J Pharmacol Exp Ther 324, 139-148.  [Abstract]

Miley MJ, Zielinska AK, Keenan JE, Bratton SM, Radominska-Pandya A, Redinbo MR. (2007) Crystal structure of the cofactor-binding domain of the human phase II drug-metabolizing enzyme UDP-glucuronosyltransferase 2B7. J Mol Biol 369, 498-511.  [Abstract]

Xiong, Y., Bernardi, D., Bratton, S., Ward, M. D., Battaglia, E., Finel, M., Drake, R., and Radominska-Pandya, A. (2006) Phenylalanine90 and 93 are amino acids localized within the phenol binding site of human UDP-glucuronosyltransferase 1A10 as determined by photoaffinity labeling, mass spectrometry, and site-directed mutagenesis. Biochemistry 21, 322-32.  [Abstract]

Lu, Y., Heydel, J. M., Li, X., Bratton, S., Lindblom, T., and Radominska-Pandya, A. (2005) Lithocholic acid decreases expression of UGT2B7 in Caco-2 cells: a potential role for a negative farnesoid X receptor response element. Drug Metab Dispos 33, 937-46.  [Abstract]

Xie, W., Yeuh, M. F., Radominska-Pandya, A., Saini, S. P., Negishi, Y., Bottroff, B. S., Cabrera, G. Y., Tukey, R. H., and Evans, R. M. (2003) Control of steroid, heme, and carcinogen metabolism by nuclear pregnane X receptor and constitutive androstane receptor. Proc Natl Acad Sci USA 100, 4150-5.  [Abstract]

Radominska-Pandya, A., and Chen, G. (2002) Photoaffinity labeling of human retinoid X receptor beta (RXRbeta) with 9-cis-retinoic acid: identification of phytanic acid, docosahexaenoic acid, and lithocholic acid as ligands for RXRbeta. Biochemistry 41, 4883-90.  [Abstract]

Xie, W., Radominska-Pandya, A., Shi, Y., Simon, C. M., Nelson, M. C., Ong, E. S., Waxman, D. J., and Evans, R. M. (2001) An essential role for nuclear receptors SXR/PXR in detoxification of cholestatic bile acids. Proc Natl Acad Sci USA 98, 3375-80.  [Abstract]

Radominska-Pandya, A., Chen, G., Czernik, P. J., Little, J. M., Samokyszyn, V. M., Carter, C. A., and Nowak, G. (2000) Direct interaction of all-trans-retinoic acid with protein kinase C (PKC). Implications for PKC signaling and cancer therapy. J Biol Chem 275, 22324-30.  [Abstract]