title: Systems Analysis of Adaptive Responses to MAP Kinase Pathway Blockade in BRAF Mutant Melanoma.
abstract: Fifty percent of cutaneous melanomas are driven by activated BRAFV600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAFV600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and receptor tyrosine kinase (RTK) mutational status. Layered over base-line resistance was substantial upregulation of many ErbB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ErbB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Capaldo
authors.affiliation: Department of Microbiology, Immunology, and Cancer, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Devin
authors.initials: D
authors.lastname: Roller
authors.affiliation: Department of Microbiology, Immunology, and Cancer, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Axelrod
authors.affiliation: Bioinfomatics Core Facility, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Alex F
authors.initials: AF
authors.lastname: Koeppel
authors.affiliation: Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, College of Science, George Mason University, Manassas, Virginia, United States of America.
authors.forename: Emanuel F
authors.initials: EF
authors.lastname: Petricoin
authors.affiliation: Department of Surgery, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Craig L
authors.initials: CL
authors.lastname: Slingluff
authors.affiliation: Department of Microbiology, Immunology, and Cancer, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Weber
authors.affiliation: Center for Public Health Genomics, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Mackey
authors.affiliation: Department of Microbiology, Immunology, and Cancer, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gioeli
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bekiranov
mesh_terms: D019943:Amino Acid Substitution; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020125:Mutation, Missense; D050787:Proto-Oncogene Protein c-ets-2 / Q000235:genetics / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: C494069:ETS2 protein, human; D007211:Indoles; C528407:PLX 4720; D050787:Proto-Oncogene Protein c-ets-2; D013449:Sulfonamides; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf