Inhibition of mTORC1/2 overcomes resistance to MAPK pathway inhibitors mediated by PGC1α and oxidative phosphorylation in melanoma

Cancer Res. 2014 Dec 1;74(23):7037-47. doi: 10.1158/0008-5472.CAN-14-1392. Epub 2014 Oct 8.

Abstract

Metabolic heterogeneity is a key factor in cancer pathogenesis. We found that a subset of BRAF- and NRAS-mutant human melanomas resistant to the MEK inhibitor selumetinib displayed increased oxidative phosphorylation (OxPhos) mediated by the transcriptional coactivator PGC1α. Notably, all selumetinib-resistant cells with elevated OxPhos could be resensitized by cotreatment with the mTORC1/2 inhibitor AZD8055, whereas this combination was ineffective in resistant cell lines with low OxPhos. In both BRAF- and NRAS-mutant melanoma cells, MEK inhibition increased MITF expression, which in turn elevated levels of PGC1α. In contrast, mTORC1/2 inhibition triggered cytoplasmic localization of MITF, decreasing PGC1α expression and inhibiting OxPhos. Analysis of tumor biopsies from patients with BRAF-mutant melanoma progressing on BRAF inhibitor ± MEK inhibitor revealed that PGC1α levels were elevated in approximately half of the resistant tumors. Overall, our findings highlight the significance of OxPhos in melanoma and suggest that combined targeting of the MAPK and mTORC pathways may offer an effective therapeutic strategy to treat melanomas with this metabolic phenotype.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line, Tumor
  • Drug Resistance, Neoplasm
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • MAP Kinase Signaling System / drug effects*
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / metabolism
  • Microphthalmia-Associated Transcription Factor / genetics
  • Microphthalmia-Associated Transcription Factor / metabolism
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Multiprotein Complexes / antagonists & inhibitors*
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Oxidative Phosphorylation / drug effects*
  • Protein Kinase Inhibitors / pharmacology*
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism

Substances

  • MITF protein, human
  • Microphthalmia-Associated Transcription Factor
  • Multiprotein Complexes
  • Protein Kinase Inhibitors
  • Transcription Factors
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins B-raf
  • TOR Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinases