4-hydroxycoumarin and Neoplasms

In vertebrates, the glucuronidation of small lipophilic agents is catalyzed by the endoplasmic reticulum UDP-glucuronosyltransferases (UGTs). This metabolic pathway leads to the formation of water-soluble metabolites originating from normal dietary processes, cellular catabolism, or exposure to drugs and xenobiotics. This classic detoxification process, which led to the discovery nearly 50 years ago of the cosubstrate UDP-glucuronic acid (19), is now known to be carried out by 15 human UGTs. Characterization of the individual gene products using cDNA expression experiments has led to the identification of over 350 individual compounds that serve as substrates for this superfamily of proteins. This data, coupled with the introduction of sophisticated RNA detection techniques designed to elucidate patterns of gene expression of the UGT superfamily in human liver and extrahepatic tissues of the gastrointestinal tract, has aided in understanding the contribution of glucuronidation toward epithelial first-pass metabolism. In addition, characterization of the UGT1A locus and genetic studies directed at understanding the role of bilirubin glucuronidation and the biochemical basis of the clinical symptoms found in unconjugated hyperbilirubinemia have uncovered the structural gene polymorphisms associated with Crigler-Najjar's and Gilbert's syndrome. The role of the UGTs in metabolism and different disease states in humans is the topic of this review.

Topics: Autoimmunity; Chromosome Mapping; Glucuronides; Glucuronosyltransferase; Humans; Hyperbilirubinemia; Neoplasms; Steroids; Terminology as Topic

A series of coumarins incorporating hydroxy-, chloro- and/or chloromethyl-moieties in positions 3-, 4-, 6- and 7- of the heterocyclic ring were investigated for the inhibition of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). These coumarins were very weak or ineffective as inhibitors of the house-keeping, offtarget isoforms CA I and II, but showed effective, submicromolar inhibition of the transmembrane, tumor-associated isoforms CA IX and XII. The nature and position of the groups substituting the coumarin ring greatly influenced CA inhibitory properties. 6-Hydroxycoumarin showed K(I)s >100 microM against CA I and II, of 0.198 microM against CA IX and of 0.683 microM against CA XII, being thus a selective, efficient inhibitor for the tumor-associated over cytosolic isoforms. These compounds are also excellent leads for designing isoform-selective enzyme inhibitors.

Topics: Antigens, Neoplasm; Binding Sites; Carbonic Anhydrase I; Carbonic Anhydrase II; Carbonic Anhydrase Inhibitors; Carbonic Anhydrase IX; Carbonic Anhydrases; Computer Simulation; Coumarins; Humans; Neoplasms