title: Synergistic antitumour activity of RAF265 and ZSTK474 on human TT medullary thyroid cancer cells.
abstract: Medullary thyroid cancer (MTC) is an aggressive malignancy responsible for up to 14% of all thyroid cancer-related deaths. It is characterized by point mutations in the rearranged during transfection (RET) proto-oncogene. The activated RET kinase is known to signal via extracellular signal regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K), leading to enhanced proliferation and resistance to apoptosis. In the present work, we have investigated the effect of two serine/threonine-protein kinase B-Raf (BRAF) inhibitors (RAF265 and SB590885), and a PI3K inhibitor (ZSTK474), on RET-mediated signalling and proliferation in a MTC cell line (TT cells) harbouring the RETC634W activating mutation. The effects of the inhibitors on VEGFR2, PI3K/Akt and mitogen-activated protein kinases signalling pathways, cell cycle, apoptosis and calcitonin production were also investigated. Only the RAF265+ ZSTK474 combination synergistically reduced the viability of treated cells. We observed a strong decrease in phosphorylated VEGFR2 for RAF265+ ZSTK474 and a signal reduction in activated Akt for ZSTK474. The activated ERK signal also decreased after RAF265 and RAF265+ ZSTK474 treatments. Alone and in combination with ZSTK474, RAF265 induced a sustained increase in necrosis. Only RAF265, alone and combined with ZSTK474, prompted a significant drop in calcitonin production. Combination therapy using RAF265 and ZSTK47 proved effective in MTC, demonstrating a cytotoxic effect. As the two inhibitors have been successfully tested individually in clinical trials on other human cancers, our preclinical data support the feasibility of their combined use in aggressive MTC.
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Loris
authors.initials: L
authors.lastname: Bertazza
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Susi
authors.initials: S
authors.lastname: Barollo
authors.affiliation: 5th Chair of Internal Medicine, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Claudia Maria
authors.initials: CM
authors.lastname: Radu
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Cavedon
authors.affiliation: 5th Chair of Internal Medicine, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Simioni
authors.affiliation: Department of Laboratory Medicine, Padua University Hospital, Padua, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Faggian
authors.affiliation: Department of Laboratory Medicine, Padua University Hospital, Padua, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Plebani
authors.affiliation: Department of Surgical, Oncological and Gastroenterological Sciences (DiSCOG), Surgery Unit, University of Padua, Padua, Italy.
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Pelizzo
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Rubin
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Boscaro
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Pezzani
authors.affiliation: Endocrinology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Mian
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002116:Calcitonin / Q000235:genetics / Q000378:metabolism; D018278:Carcinoma, Neuroendocrine / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology / Q000627:therapeutic use*; D020128:Inhibitory Concentration 50; D008954:Models, Biological; D000090063:Proto-Oncogene Mas; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use*; D015398:Signal Transduction / Q000187:drug effects; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D014227:Triazines / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011725:Pyridines; C508204:SB-590885; D014227:Triazines; C510150:ZSTK474; D002116:Calcitonin; C559019:RAF265
keywords: BRAF; RAF265; RET; SB590885; ZSTK474; medullary thyroid cancer