title: A second target of benzamide riboside: dihydrofolate reductase.
abstract: Dihydrofolate reductase (DHFR) is an essential enzyme involved in de novo purine and thymidine biosynthesis. For several decades, selective inhibition of DHFR has proven to be a potent therapeutic approach in the treatment of various cancers including acute lymphoblastic leukemia, non-Hodgkin's lymphoma, osteogenic sarcoma, carcinoma of the breast, and head and neck cancer. Therapeutic success with DHFR inhibitor methotrexate (MTX) has been compromised in the clinic, which limits the success of MTX treatment by both acquired and intrinsic resistance mechanisms. We report that benzamide riboside (BR), via anabolism to benzamide adenine dinucleotide (BAD) known to potently inhibit inosine monophosphate dehydrogenase (IMPDH), also inhibits cell growth through a mechanism involving downregulation of DHFR protein. Evidence to support this second site of action of BR includes the finding that CCRF-CEM/R human T-cell lymphoblasic leukemia cells, resistant to MTX as a consequence of gene amplification and overexpression of DHFR, are more resistant to BR than are parental cells. Studies of the mechanism by which BR lowers DHFR showed that BR, through its metabolite BAD, reduced NADP and NADPH cellular levels by inhibiting nicotinamide adenine dinucleotide kinase (NADK). As consequence of the lack of NADPH, DHFR was shown to be destabilized. We suggest that, inhibition of NADK is a new approach to downregulate DHFR and to inhibit cell growth.
authors.affiliation: Department of Medicine, Biochemistry and Pharmacology, Robert Wood Johnson Medical School, New Brunswick, NJ, USA.
authors.forename: Breton
authors.initials: B
authors.lastname: Roussel
authors.forename: Nadine
authors.initials: N
authors.lastname: Johnson-Farley
authors.forename: John E
authors.initials: JE
authors.lastname: Kerrigan
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Scotto
authors.forename: Debabrata
authors.initials: D
authors.lastname: Banerjee
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Felczak
authors.forename: Krzysztof W
authors.initials: KW
authors.lastname: Pankiewicz
authors.forename: Murugesan
authors.initials: M
authors.lastname: Gounder
authors.forename: HongXia
authors.initials: H
authors.lastname: Lin
authors.forename: Emine Ercikan
authors.initials: EE
authors.lastname: Abali
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Bertino
mesh_terms: D000227:Adenine Nucleotides / Q000235:genetics / Q000378:metabolism; D001549:Benzamides / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008727:Methotrexate / Q000494:pharmacology; D058990:Molecular Targeted Therapy; D009249:NADP / Q000235:genetics / Q000378:metabolism; D009705:Nucleosides / Q000494:pharmacology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000227:Adenine Nucleotides; D001549:Benzamides; D009705:Nucleosides; C076145:3-(1-deoxyribofuranosyl)benzamide; C100366:benzamide adenine nucleotide; D009249:NADP; D007168:IMP Dehydrogenase; D013762:Tetrahydrofolate Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; D008727:Methotrexate