title: Truncated RAF kinases drive resistance to MET inhibition in MET-addicted cancer cells.
abstract: Constitutively active receptor tyrosine kinases (RTKs) are known oncogenic drivers and provide valuable therapeutic targets in many cancer types. However, clinical efficacy of RTK inhibitors is limited by intrinsic and acquired resistance. To identify genes conferring resistance to inhibition of the MET RTK, we conducted a forward genetics screen in the GTL-16 gastric cancer cell line, carrying MET amplification and exquisitely sensitive to MET inhibition. Cells were transduced with three different retroviral cDNA expression libraries and selected for growth in the presence of the MET inhibitor PHA-665752. Selected cells displayed robust and reproducible enrichment of library-derived cDNAs encoding truncated forms of RAF1 and BRAF proteins, whose silencing reversed the resistant phenotype. Transduction of naïve GTL-16 cells with truncated, but not full length, RAF1 and BRAF conferred in vitro and in vivo resistance to MET inhibitors, which could be reversed by MEK inhibition. Induction of resistance by truncated RAFs was confirmed in other MET-addicted cell lines, and further extended to EGFR-addicted cells. These data show that truncated RAF1 and BRAF proteins, recently described as products of genomic rearrangements in gastric cancer and other malignancies, have the ability to render neoplastic cells resistant to RTK-targeted therapy.
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Italy.
authors.forename: Consalvo
authors.initials: C
authors.lastname: Petti
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Italy. Department of Oncology, University of Torino, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Picco
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Martelli
authors.affiliation: Department of Oncology, University of Torino, Italy. Istituto Nazionale Biostrutture e Biosistemi, Roma, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Trisolini
authors.affiliation: Biodigitalvalley Srl, Pont Saint Martin, Aosta, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Bucci
authors.affiliation: Janssen Research and Development, Oncology Discovery, Beerse, Belgium.
authors.forename: Timothy
authors.initials: T
authors.lastname: Perera
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Italy. Department of Oncology, University of Torino, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Isella
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Italy. Department of Oncology, University of Torino, Italy.
authors.forename: Enzo
authors.initials: E
authors.lastname: Medico
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival; D018076:DNA, Complementary / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D015723:Gene Library; D006801:Humans; D007211:Indoles / Q000737:chemistry; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010641:Phenotype; D047428:Protein Kinase Inhibitors / Q000737:chemistry; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D013274:Stomach Neoplasms / Q000378:metabolism*; D013450:Sulfones / Q000737:chemistry; D013997:Time Factors; D048490:raf Kinases / Q000378:metabolism*
chemical_list: C480541:5-((2,6-dichlorobenzyl)sulfonyl)-3-((3,5-dimethyl-4-((2-(pyrrolidin-1-ylmethyl)pyrrolidin-1-yl)carbonyl)-1H-pyrrol-2-yl)methylene)-1,3-dihydro-2H-indol-2-one; D018076:DNA, Complementary; D007211:Indoles; D047428:Protein Kinase Inhibitors; D013450:Sulfones; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases; C482119:BRAF protein, human; C482120:Braf protein, mouse; D048493:Proto-Oncogene Proteins B-raf; D048490:raf Kinases