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.
Copyright © 2018 Elsevier Inc. All rights reserved.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Carcinoma, Pancreatic Ductal / genetics
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Carcinoma, Pancreatic Ductal / pathology*
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Cell Line, Tumor
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ErbB Receptors / metabolism
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Glycogen Synthase Kinase 3 beta / metabolism
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Humans
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MAP Kinase Kinase 5 / metabolism*
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Mice
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Mice, Inbred NOD
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Mice, Knockout
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Mice, SCID
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3 / metabolism*
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Mitogen-Activated Protein Kinase 7 / metabolism*
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Pancreatic Neoplasms / genetics
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Pancreatic Neoplasms / pathology*
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Phosphatidylinositol 3-Kinases / metabolism
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Proto-Oncogene Proteins c-akt / metabolism
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Proto-Oncogene Proteins c-myc / metabolism*
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Proto-Oncogene Proteins p21(ras) / genetics*
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src-Family Kinases / metabolism
Substances
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MYC protein, human
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Proto-Oncogene Proteins c-myc
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Phosphatidylinositol 3-Kinases
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EGFR protein, human
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ErbB Receptors
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src-Family Kinases
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Proto-Oncogene Proteins c-akt
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MAPK1 protein, human
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MAPK3 protein, human
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MAPK7 protein, human
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinase 7
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MAP Kinase Kinase 5
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MAP2K5 protein, human
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Proto-Oncogene Proteins p21(ras)