title: Fibronectin induction abrogates the BRAF inhibitor response of BRAF V600E/PTEN-null melanoma cells.
abstract: The mechanisms by which some melanoma cells adapt to Serine/threonine-protein kinase B-Raf (BRAF) inhibitor therapy are incompletely understood. In the present study, we used mass spectrometry-based phosphoproteomics to determine how BRAF inhibition remodeled the signaling network of melanoma cell lines that were BRAF mutant and PTEN null. Short-term BRAF inhibition was associated with marked changes in fibronectin-based adhesion signaling that were PTEN dependent. These effects were recapitulated through BRAF siRNA knockdown and following treatment with chemotherapeutic drugs. Increased fibronectin expression was also observed in mouse xenograft models as well as specimens from melanoma patients undergoing BRAF inhibitor treatment. Analysis of a melanoma tissue microarray showed loss of PTEN expression to predict for a lower overall survival, with a trend for even lower survival being seen when loss of fibronectin was included in the analysis. Mechanistically, the induction of fibronectin limited the responses of these PTEN-null melanoma cell lines to vemurafenib, with enhanced cytotoxicity observed following the knockdown of either fibronectin or its receptor α5β1 integrin. This in turn abrogated the cytotoxic response to BRAF inhibition via increased AKT signaling, which prevented the induction of cell death by maintaining the expression of the pro-survival protein Mcl-1. The protection conveyed by the induction of FN expression could be overcome through combined treatment with a BRAF and PI3K inhibitor.
authors.affiliation: Department of Molecular Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: I V
authors.initials: IV
authors.lastname: Fedorenko
authors.affiliation: Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: E V
authors.initials: EV
authors.lastname: Abel
authors.affiliation: Department of Molecular Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Koomen
authors.affiliation: Department of Proteomics, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: B
authors.initials: B
authors.lastname: Fang
authors.affiliation: Department of Molecular Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.|Department of Proteomics, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Wood
authors.affiliation: Department of Biostatistics and Bioinformatics, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Y A
authors.initials: YA
authors.lastname: Chen
authors.affiliation: Department of Biostatistics and Bioinformatics, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Fisher
authors.affiliation: Department of Cutaneous Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: S
authors.initials: S
authors.lastname: Iyengar
authors.affiliation: Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Dahlman
authors.affiliation: Department of Surgery, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Wargo
authors.affiliation: Department of Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: K T
authors.initials: KT
authors.lastname: Flaherty
authors.affiliation: Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Sosman
authors.affiliation: Department of Cutaneous Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: V K
authors.initials: VK
authors.lastname: Sondak
authors.affiliation: Department of Cutaneous Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Messina
authors.affiliation: Department of Cutaneous Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: G T
authors.initials: GT
authors.lastname: Gibney
authors.affiliation: Department of Molecular Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.|Department of Cutaneous Oncology, The Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: K S M
authors.initials: KS
authors.lastname: Smalley
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005353:Fibronectins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D008545:Melanoma / Q000473:pathology*; D051379:Mice; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000172:deficiency* / Q000235:genetics*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D040901:Proteomics; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D005353:Fibronectins; D039081:Integrin alpha5beta1; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human