SHOC2 and CRAF mediate ERK1/2 reactivation in mutant NRAS-mediated resistance to RAF inhibitor.
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.
Department of Cancer Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Fred M
FM
Kaplan
Curtis H
CH
Kugel
Neda
N
Dadpey
Yongping
Y
Shao
Ethan V
EV
Abel
Andrew E
AE
Aplin
D019943:Amino Acid Substitution; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000235:genetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D013449:Sulfonamides / Q000494:pharmacology*
D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; C528407:PLX 4720; C112913:SHOC2 protein, human; D013449:Sulfonamides; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016283:Proto-Oncogene Proteins p21(ras)