title: Growth arrest by activated BRAF and MEK inhibition in human anaplastic thyroid cancer cells.
abstract: Anaplastic thyroid cancer (ATC) is a rare malignancy that progresses extremely aggressively and often results in dismal prognosis. We investigated the efficacy of inhibiting the activated RAS/RAF/MEK pathway in ATC cells aiming to clarify the mechanism of effect and resistance. Four human ATC cell lines (ACT-1, OCUT-2, OCUT-4 and OCUT-6) were used. OCUT-4 had a BRAF mutation. OCUT-2 had both BRAF and PI3KCA mutations. ACT-1 and OCUT-6 had wild-type BRAF and NRAS mutations. The effects of dabrafenib, a selective inhibitor of the BRAFV600E kinase, and trametinib, a reversible inhibitor of MEK activity, were investigated. Dabrafenib strongly inhibited the viability in BRAF mutated cells by demonstrating G0/G1-arrest via the downregulation of MEK/ERK phosphorylation. Upregulated phosphorylation of MEK was observed in RAS mutated cells after dabrafenib treatment and caused VEGF upregulation, but was not related to the cellular proliferation. Trametinib inhibited the cellular viability to variable degrees in every cell by downregulating ERK phosphorylation. Dual blockade by both inhibitors demonstrated clear cytostatic effect in all the cells. OCUT-4 showed the weakest sensitivity to trametinib, no additional effect of either inhibitor in combination with the other, and an increase of SNAI1 mRNA expression after treatment with inhibitors, suggesting a mechanism for resistance. Our findings demonstrated the efficacy of a mutation-selective BRAF inhibitor and a MEK inhibitor in human ATC cells in a genetic alteration-specific manner.
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Kento
authors.initials: K
authors.lastname: Kurata
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Onoda
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Noda
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Kashiwagi
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Asano
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Kosei
authors.initials: K
authors.lastname: Hirakawa
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan.
authors.forename: Masaichi
authors.initials: M
authors.lastname: Ohira
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D020558:GTP Phosphohydrolases / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D010091:Oximes / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000235:genetics; D011728:Pyridones / Q000494:pharmacology*; D011744:Pyrimidinones / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D000071250:Snail Family Transcription Factors / Q000235:genetics; D065646:Thyroid Carcinoma, Anaplastic / Q000188:drug therapy* / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010091:Oximes; C503859:PI3KCA protein, human; D047428:Protein Kinase Inhibitors; D011728:Pyridones; D011744:Pyrimidinones; D012333:RNA, Messenger; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C560077:trametinib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human; C561627:dabrafenib