KRAS Suppression-Induced Degradation of MYC Is Antagonized by a MEK5-ERK5 Compensatory Mechanism

Cancer Cell. 2018 Nov 12;34(5):807-822.e7. doi: 10.1016/j.ccell.2018.10.001.

Abstract

Our recent ERK1/2 inhibitor analyses in pancreatic ductal adenocarcinoma (PDAC) indicated ERK1/2-independent mechanisms maintaining MYC protein stability. To identify these mechanisms, we determined the signaling networks by which mutant KRAS regulates MYC. Acute KRAS suppression caused rapid proteasome-dependent loss of MYC protein, through both ERK1/2-dependent and -independent mechanisms. Surprisingly, MYC degradation was independent of PI3K-AKT-GSK3β signaling and the E3 ligase FBWX7. We then established and applied a high-throughput screen for MYC protein degradation and performed a kinome-wide proteomics screen. We identified an ERK1/2-inhibition-induced feedforward mechanism dependent on EGFR and SRC, leading to ERK5 activation and phosphorylation of MYC at S62, preventing degradation. Concurrent inhibition of ERK1/2 and ERK5 disrupted this mechanism, synergistically causing loss of MYC and suppressing PDAC growth.

Keywords: EGFR; ERK; ERK5; FBXW7; KRAS; MYC; PI3K; SRC; pancreatic cancer.

Publication types

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

MeSH terms

  • Animals
  • Carcinoma, Pancreatic Ductal / genetics
  • Carcinoma, Pancreatic Ductal / pathology*
  • Cell Line, Tumor
  • ErbB Receptors / metabolism
  • Glycogen Synthase Kinase 3 beta / metabolism
  • Humans
  • MAP Kinase Kinase 5 / metabolism*
  • Mice
  • Mice, Inbred NOD
  • Mice, Knockout
  • Mice, SCID
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Mitogen-Activated Protein Kinase 7 / metabolism*
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / pathology*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-myc / metabolism*
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • src-Family Kinases / metabolism

Substances

  • MYC protein, human
  • Proto-Oncogene Proteins c-myc
  • Phosphatidylinositol 3-Kinases
  • EGFR protein, human
  • ErbB Receptors
  • src-Family Kinases
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Proto-Oncogene Proteins c-akt
  • MAPK1 protein, human
  • MAPK3 protein, human
  • MAPK7 protein, human
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinase 7
  • MAP Kinase Kinase 5
  • MAP2K5 protein, human
  • Proto-Oncogene Proteins p21(ras)