title: BRAF associated autophagy exploitation: BRAF and autophagy inhibitors synergise to efficiently overcome resistance of BRAF mutant colorectal cancer cells.
abstract: Autophagy is the basic catabolic mechanism that involves cell degradation of unnecessary or dysfunctional cellular components. Autophagy has a controversial role in cancer--both in protecting against tumor progression by isolation of damaged organelles, or by potentially contributing to cancer growth. The impact of autophagy in RAS induced transformation still remains to be further analyzed based on the differential effect of RAS isoforms and tumor cell context. In the present study, the effect of KRAS/BRAF/PIK3CA oncogenic pathways on the autophagic cell properties and on main components of the autophagic machinery like p62 (SQSTM1), Beclin-1 (BECN1) and MAP1LC3 (LC3) in colon cancer cells was investigated. This study provides evidence that BRAF oncogene induces the expression of key autophagic markers, like LC3 and BECN1 in colorectal tumor cells. Herein, PI3K/AKT/MTOR inhibitors induce autophagic tumor properties, whereas RAF/MEK/ERK signalling inhibitors reduce expression of autophagic markers. Based on the ineffectiveness of BRAFV600E inhibitors in BRAFV600E bearing colorectal tumors, the BRAF related autophagic properties in colorectal cancer cells are further exploited, by novel combinatorial anti-cancer protocols. Strong evidence is provided here that pre-treatment of autophagy inhibitor 3-MA followed by its combination with BRAFV600E targeting drug PLX4720 can synergistically sensitize resistant colorectal tumors. Notably, colorectal cancer cells are very sensitive to mono-treatments of another autophagy inhibitor, Bafilomycin A1. The findings of this study are expected to provide novel efficient protocols for treatment of otherwise resistant colorectal tumors bearing BRAFV600E, by exploiting the autophagic properties induced by BRAF oncogene.
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Goulielmaki
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Koustas
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Eirini
authors.initials: E
authors.lastname: Moysidou
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Margarita
authors.initials: M
authors.lastname: Vlassi
authors.affiliation: Institute for Advanced Study, Kyushu University, Fukuoka, Japan.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sasazuki
authors.affiliation: Department of Cell Biology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Senji
authors.initials: S
authors.lastname: Shirasawa
authors.affiliation: 3rd Department of Surgery, General Hospital of Athens G. Gennimatas, Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Zografos
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Eftychia
authors.initials: E
authors.lastname: Oikonomou
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
authors.forename: Alexander
authors.initials: A
authors.lastname: Pintzas
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000071186:Beclin-1 / Q000378:metabolism; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D000071456:Sequestosome-1 Protein / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors
chemical_list: D000970:Antineoplastic Agents; D000071186:Beclin-1; D058534:Class I Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D007211:Indoles; D018942:Macrolides; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D016283:Proto-Oncogene Proteins p21(ras); D000071456:Sequestosome-1 Protein; D013449:Sulfonamides; D058570:TOR Serine-Threonine Kinases; C491997:BECN1 protein, human; C117307:KRAS protein, human; C477012:MAP1LC3A protein, human; C528407:PLX 4720; C099718:SQSTM1 protein, human; C040929:bafilomycin A1; C546842:MTOR protein, human; C484760:PIK3CA protein, human; C482119:BRAF protein, human
keywords: BRAF inhibitors; autophagy inhibitors; colorectal cancer; synergistic treatments