title: Identification of a novel inhibitor (NSC 665564) of dihydroorotate dehydrogenase with a potency equivalent to brequinar.
abstract: A novel inhibitor of dihydroorotate dehydrogenase (DHO-DH) has been discovered using data from the National Cancer Institute's in vitro drug screen. Upon analysis of cytotoxicity results from the sixty tumor cell lines used in this screen, the COMPARE program predicted that NSC 665564 was likely to have the same mechanism of inhibition as brequinar, a known potent inhibitor of DHO-DH. We validated this prediction experimentally using MOLT-4 lymphoblast and found the IC50 of brequinar (0.5 microM) and NSC 665564 (0.3 microM) were comparable and that this induced cytotoxicity was reversed by either uridine or cytidine. The enzyme target of NSC 665564 was shown to be identical to that of brequinar when incubation with each drug followed by a 1 h pulse with [14C] sodium bicarbonate resulted in cellular accumulation of [14C]N-carbamyl-L-aspartic acid and [14C]L-dihydroorotic acid, with concurrent marked depletion of CTP and UTP. The Ki's for NSC 665564 and brequinar were 0.14 and 0.24 microM, respectively, when partially purified MOLT-4 mitochondria (the site of DHO-DH) were used. These results show that mechanistic predictions obtained using correlations from the COMPARE algorithm are independent of structure since the structure of NSC 665564 is dissimilar to that of other established DHO-DH inhibitors.
authors.affiliation: Laboratory of Medicinal Chemistry, National Cancer Institute, National Institutes of Health, Bethesda Maryland 20892, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Cleaveland
authors.forename: D W
authors.initials: DW
authors.lastname: Zaharevitz
authors.forename: J A
authors.initials: JA
authors.lastname: Kelley
authors.forename: K
authors.initials: K
authors.lastname: Paull
authors.forename: D A
authors.initials: DA
authors.lastname: Cooney
authors.forename: H
authors.initials: H
authors.lastname: Ford
mesh_terms: D000970:Antineoplastic Agents / Q000633:toxicity*; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001713:Biphenyl Compounds / Q000633:toxicity*; D001943:Breast Neoplasms; D002243:Carbolines / Q000633:toxicity*; D002289:Carcinoma, Non-Small-Cell Lung; D016543:Central Nervous System Neoplasms; D003110:Colonic Neoplasms; D000090722:Dihydroorotate Dehydrogenase; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms; D007700:Kinetics; D007938:Leukemia; D008175:Lung Neoplasms; D008297:Male; D008545:Melanoma; D008928:Mitochondria / Q000201:enzymology; D009963:Orotic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D010051:Ovarian Neoplasms; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D011471:Prostatic Neoplasms; D012265:Ribonucleotides / Q000378:metabolism; D017693:Sodium Bicarbonate / Q000378:metabolism; D012984:Software; D014407:Tumor Cells, Cultured; D011798:Quinaldines
chemical_list: D000970:Antineoplastic Agents; D001224:Aspartic Acid; D001713:Biphenyl Compounds; D002243:Carbolines; D000090722:Dihydroorotate Dehydrogenase; D004791:Enzyme Inhibitors; D009963:Orotic Acid; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D012265:Ribonucleotides; D017693:Sodium Bicarbonate; C100325:NSC 665564; C004768:4,5-dihydroorotic acid; C046943:brequinar; D011798:Quinaldines; C006893:ureidosuccinic acid