Direct role of nucleotide metabolism in C-MYC-dependent proliferation of melanoma cells

Cell Cycle. 2008 Aug;7(15):2392-400. doi: 10.4161/cc.6390. Epub 2008 Jun 3.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Proliferation* / drug effects
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • IMP Dehydrogenase / genetics
  • IMP Dehydrogenase / metabolism
  • IMP Dehydrogenase / physiology
  • Melanocytes / metabolism
  • Melanoma / genetics
  • Melanoma / metabolism*
  • Melanoma / pathology*
  • Nucleotides / biosynthesis*
  • Promoter Regions, Genetic
  • Protein Binding
  • Proto-Oncogene Proteins c-myc / antagonists & inhibitors
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism
  • Proto-Oncogene Proteins c-myc / physiology*
  • RNA, Small Interfering / pharmacology
  • Ribose-Phosphate Pyrophosphokinase / genetics
  • Ribose-Phosphate Pyrophosphokinase / metabolism
  • Ribose-Phosphate Pyrophosphokinase / physiology
  • Thymidylate Synthase / genetics
  • Thymidylate Synthase / metabolism
  • Thymidylate Synthase / physiology
  • Transfection
  • Tumor Cells, Cultured

Substances

  • Nucleotides
  • Proto-Oncogene Proteins c-myc
  • RNA, Small Interfering
  • IMP Dehydrogenase
  • IMPDH2 protein, human
  • Thymidylate Synthase
  • Ribose-Phosphate Pyrophosphokinase