title: Mitogen-activated protein kinase (MAPK) hyperactivation and enhanced NRAS expression drive acquired vemurafenib resistance in V600E BRAF melanoma cells.
abstract: Although targeting the V600E activating mutation in the BRAF gene, the most common genetic abnormality in melanoma, has shown clinical efficacy in melanoma patients, response is, invariably, short lived. To better understand mechanisms underlying this acquisition of resistance to BRAF-targeted therapy in previously responsive melanomas, we induced vemurafenib resistance in two V600E BRAF+ve melanoma cell lines, A375 and DM443, by serial in vitro vemurafenib exposure. The resulting approximately 10-fold more vemurafenib-resistant cell lines, A375rVem and D443rVem, had higher growth rates and showed differential collateral resistance to cisplatin, melphalan, and temozolomide. The acquisition of vemurafenib resistance was associated with significantly increased NRAS levels in A375rVem and D443rVem, increased activation of the prosurvival protein, AKT, and the MAPKs, ERK, JNK, and P38, which correlated with decreased levels of the MAPK inhibitor protein, GSTP1. Despite the increased NRAS, whole exome sequencing showed no NRAS gene mutations. Inhibition of all three MAPKs and siRNA-mediated NRAS suppression both reversed vemurafenib resistance significantly in A375rVem and DM443rVem. Together, the results indicate a mechanism of acquired vemurafenib resistance in V600E BRAF+ve melanoma cells that involves increased activation of all three human MAPKs and the PI3K pathway, as well as increased NRAS expression, which, contrary to previous reports, was not associated with mutations in the NRAS gene. The data highlight the complexity of the acquired vemurafenib resistance phenotype and the challenge of optimizing BRAF-targeted therapy in this disease. They also suggest that targeting the MAPKs and/or NRAS may provide a strategy to mitigate such resistance in V600E BRAF+ve melanoma.
authors: From the Division of Surgical Oncology and.
authors: Michael
authors: M
authors: Lidsky
authors: the Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710.
authors: Gamil
authors: G
authors: Antoun
authors: From the Division of Surgical Oncology and.
authors: Paul
authors: P
authors: Speicher
authors: the Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710.
authors: Bartley
authors: B
authors: Adams
authors: From the Division of Surgical Oncology and.
authors: Ryan
authors: R
authors: Turley
authors: From the Division of Surgical Oncology and.
authors: Christi
authors: C
authors: Augustine
authors: From the Division of Surgical Oncology and.
authors: Douglas
authors: D
authors: Tyler
authors: the Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710 francis.aliosman@duke.edu.
authors: Francis
authors: F
authors: Ali-Osman
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics* / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D000077484:Vemurafenib
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; D008565:Membrane Proteins; D013449:Sulfonamides; D000077484:Vemurafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human
keywords: Acquired Drug Resistance; Extracellular Signal-regulated Kinase (ERK); Melanoma; Mitogen-activated Protein Kinase (MAPK); NRAS; Vemurafenib; c-Jun N-terminal Kinase (JNK); p38