title: A melanocyte lineage program confers resistance to MAP kinase pathway inhibition.
abstract: Malignant melanomas harbouring point mutations (Val600Glu) in the serine/threonine-protein kinase BRAF (BRAF(V600E)) depend on RAF-MEK-ERK signalling for tumour cell growth. RAF and MEK inhibitors show remarkable clinical efficacy in BRAF(V600E) melanoma; however, resistance to these agents remains a formidable challenge. Global characterization of resistance mechanisms may inform the development of more effective therapeutic combinations. Here we carried out systematic gain-of-function resistance studies by expressing more than 15,500 genes individually in a BRAF(V600E) melanoma cell line treated with RAF, MEK, ERK or combined RAF-MEK inhibitors. These studies revealed a cyclic-AMP-dependent melanocytic signalling network not previously associated with drug resistance, including G-protein-coupled receptors, adenyl cyclase, protein kinase A and cAMP response element binding protein (CREB). Preliminary analysis of biopsies from BRAF(V600E) melanoma patients revealed that phosphorylated (active) CREB was suppressed by RAF-MEK inhibition but restored in relapsing tumours. Expression of transcription factors activated downstream of MAP kinase and cAMP pathways also conferred resistance, including c-FOS, NR4A1, NR4A2 and MITF. Combined treatment with MAPK-pathway and histone-deacetylase inhibitors suppressed MITF expression and cAMP-mediated resistance. Collectively, these data suggest that oncogenic dysregulation of a melanocyte lineage dependency can cause resistance to RAF-MEK-ERK inhibition, which may be overcome by combining signalling- and chromatin-directed therapeutics.
authors.affiliation: 1] The Broad Institute of Harvard University and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, Massachusetts 02142, USA [2] Department of Medical Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, Massachusetts 02115, USA [3] Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115, USA.
authors.forename: Cory M
authors.initials: CM
authors.lastname: Johannessen
authors.forename: Laura A
authors.initials: LA
authors.lastname: Johnson
authors.forename: Federica
authors.initials: F
authors.lastname: Piccioni
authors.forename: Aisha
authors.initials: A
authors.lastname: Townes
authors.forename: Dennie T
authors.initials: DT
authors.lastname: Frederick
authors.forename: Melanie K
authors.initials: MK
authors.lastname: Donahue
authors.forename: Rajiv
authors.initials: R
authors.lastname: Narayan
authors.forename: Keith T
authors.initials: KT
authors.lastname: Flaherty
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Wargo
authors.forename: David E
authors.initials: DE
authors.lastname: Root
authors.forename: Levi A
authors.initials: LA
authors.lastname: Garraway
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D050882:CREB-Binding Protein / Q000378:metabolism; D045744:Cell Line, Tumor; D019070:Cell Lineage; D000242:Cyclic AMP / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D008544:Melanocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008545:Melanoma / Q000201:enzymology / Q000503:physiopathology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D014157:Transcription Factors; D000242:Cyclic AMP; D050882:CREB-Binding Protein; D020928:Mitogen-Activated Protein Kinases