title: Direct role of nucleotide metabolism in C-MYC-dependent proliferation of melanoma cells.
abstract: To identify C-MYC targets rate-limiting for proliferation of malignant melanoma, we stably inhibited C-MYC in several human metastatic melanoma lines via lentivirus-based shRNAs approximately to the levels detected in normal melanocytes. C-MYC depletion did not significantly affect levels of E2F1 protein reported to regulate expression of many S-phase specific genes, but resulted in the repression of several genes encoding enzymes rate-limiting for dNTP metabolism. These included thymidylate synthase (TS), inosine monophosphate dehydrogenase 2 (IMPDH2) and phosphoribosyl pyrophosphate synthetase 2 (PRPS2). C-MYC depletion also resulted in reduction in the amounts of deoxyribonucleoside triphosphates (dNTPs) and inhibition of proliferation. shRNA-mediated suppression of TS, IMPDH2 or PRPS2 resulted in the decrease of dNTP pools and retardation of the cell cycle progression of melanoma cells in a manner similar to that of C-MYC-depletion in those cells. Reciprocally, concurrent overexpression of cDNAs for TS, IMPDH2 and PRPS2 delayed proliferative arrest caused by inhibition of C-MYC in melanoma cells. Overexpression of C-MYC in normal melanocytes enhanced expression of the above enzymes and increased individual dNTP pools. Analysis of in vivo C-MYC interactions with TS, IMPDH2 and PRPS2 genes confirmed that they are direct C-MYC targets. Moreover, all three proteins express at higher levels in cells from several metastatic melanoma lines compared to normal melanocytes. Our data establish a novel functional link between C-MYC and dNTP metabolism and identify its role in proliferation of tumor cells.
authors.affiliation: Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
authors.forename: Sudha
authors.initials: S
authors.lastname: Mannava
authors.forename: Vladimir
authors.initials: V
authors.lastname: Grachtchouk
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Wheeler
authors.forename: Michael
authors.initials: M
authors.lastname: Im
authors.forename: Dazhong
authors.initials: D
authors.lastname: Zhuang
authors.forename: Elena G
authors.initials: EG
authors.lastname: Slavina
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Mathews
authors.forename: Donna S
authors.initials: DS
authors.lastname: Shewach
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Nikiforov
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007168:IMP Dehydrogenase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008544:Melanocytes / Q000378:metabolism; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009711:Nucleotides / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D012268:Ribose-Phosphate Pyrophosphokinase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D009711:Nucleotides; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D007168:IMP Dehydrogenase; C501687:IMPDH2 protein, human; D013940:Thymidylate Synthase; D012268:Ribose-Phosphate Pyrophosphokinase