Abstract
ERK1/2 signaling is frequently dysregulated in tumors through BRAF mutation. Targeting mutant BRAF with vemurafenib frequently elicits therapeutic responses; however, durable effects are often limited by ERK1/2 pathway reactivation via poorly defined mechanisms. We generated mutant BRAF(V600E) melanoma cells that exhibit resistance to PLX4720, the tool compound for vemurafenib, that co-expressed mutant (Q61K) NRAS. In these BRAF(V600E)/NRAS(Q61K) co-expressing cells, re-activation of the ERK1/2 pathway during PLX4720 treatment was dependent on NRAS. Expression of mutant NRAS in parental BRAF(V600) cells was sufficient to by-pass PLX4720 effects on ERK1/2 signaling, entry into S phase and susceptibility to apoptosis in a manner dependent on the RAF binding site in NRAS. ERK1/2 activation in BRAF(V600E)/NRAS(Q61K) cells required CRAF only in the presence of PLX4720, indicating a switch in RAF isoform requirement. Both ERK1/2 activation and resistance to apoptosis of BRAF(V600E)/NRAS(Q61K) cells in the presence of PLX4720 was modulated by SHOC-2/Sur-8 expression, a RAS-RAF scaffold protein. These data show that NRAS mutations confer resistance to RAF inhibitors in mutant BRAF cells and alter RAF isoform and scaffold molecule requirements to re-activate the ERK1/2 pathway.
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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Amino Acid Substitution
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Cell Line, Tumor
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Drug Resistance, Neoplasm / drug effects*
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Drug Resistance, Neoplasm / genetics
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Enzyme Activation / drug effects
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Enzyme Activation / genetics
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Humans
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Indoles / pharmacology*
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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MAP Kinase Signaling System / drug effects*
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MAP Kinase Signaling System / genetics
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Mitogen-Activated Protein Kinase 1 / genetics
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3 / genetics
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Mitogen-Activated Protein Kinase 3 / metabolism*
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Mutation, Missense
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Proto-Oncogene Proteins B-raf / genetics
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Proto-Oncogene Proteins B-raf / metabolism
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Proto-Oncogene Proteins c-raf / genetics
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Proto-Oncogene Proteins c-raf / metabolism*
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Proto-Oncogene Proteins p21(ras) / antagonists & inhibitors*
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Proto-Oncogene Proteins p21(ras) / genetics
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Proto-Oncogene Proteins p21(ras) / metabolism
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S Phase / drug effects
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S Phase / genetics
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Sulfonamides / pharmacology*
Substances
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Indoles
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Intracellular Signaling Peptides and Proteins
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PLX 4720
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SHOC2 protein, human
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Sulfonamides
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BRAF protein, human
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Proto-Oncogene Proteins B-raf
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Proto-Oncogene Proteins c-raf
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MAPK1 protein, human
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Proto-Oncogene Proteins p21(ras)