title: Synergistic effect of pasireotide and teriflunomide in carcinoids in vitro.
abstract: OBJECTIVE
  Somatostatin (SST) analogs are mainstay for controlling tumor proliferation and hormone secretion in carcinoid patients. Recent data suggest that extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation may potentiate the anti-tumor effects of SST analogs in carcinoids. Additionally, ERK1/2 phosphorylating agents have been shown to suppress biomarker expression in carcinoids. Thus, Raf-1/MEK/ERK1/2 pathway activating drugs may be synergistic with SST analogs such as pasireotide (SOM230), which may be more effective than others in its class given its elevated receptor affinity and broader binding spectrum. Here, we investigate the effects of SOM230 in combination with teriflunomide (TFN), a Raf-1 activator, in a human carcinoid cell line.
  
  
  METHODS
  Human pancreatic carcinoid cells (BON) were incubated in TFN, SOM230 or a combination. Cell proliferation was measured using a rapid colorimetric assay. Western analysis was performed to analyze expression levels of achaete-scute complex-like 1 (ASCL1), chromogranin A (CgA), phosphorylated and total ERK1/2, and markers for apoptosis.
  
  
  RESULTS
  Combination treatment with SOM230 and TFN reduced cell growth beyond the additive effect of either drug alone. Combination indices (CI) fell below 1, thus quantifiably verifying synergy between both drugs as per the Chou-Talalay CI scale. Combined treatment also reduced ASCL1 and CgA expression beyond the additive effect of either drug alone. Furthermore, it increased levels of phosphorylated ERK1/2, cleaved poly(ADP)-ribose polymerase and caspase-3, and reduced levels of anti-apoptotic biomarkers. Elevated phosphorylated ERK1/2 expression following combination therapy may underlie the synergistic interaction between the two drugs.
  
  
  CONCLUSIONS
  Since efficacy is achieved at lower doses, combination therapy may palliate symptoms at low toxicity levels. Because each drug has already been evaluated in clinical trials, combinatorial drug trials are warranted.
authors.affiliation: University of Wisconsin School of Medicine and Public Health, Endocrine Surgery Research Laboratories, Department of Surgery, Madison, USA.
authors.forename: Yash
authors.initials: Y
authors.lastname: Somnay
authors.forename: Herbert
authors.initials: H
authors.lastname: Chen
authors.forename: Muthusamy
authors.initials: M
authors.lastname: Kunnimalaiyaan
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D018278:Carcinoma, Neuroendocrine / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D053379:Chromogranin A / Q000378:metabolism; D003437:Crotonates / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005770:Gastrointestinal Neoplasms / Q000378:metabolism*; D006801:Humans; D006885:Hydroxybutyrates; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009570:Nitriles; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000494:pharmacology; D014052:Toluidines / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D051792:Basic Helix-Loop-Helix Proteins; D053379:Chromogranin A; D003437:Crotonates; D006885:Hydroxybutyrates; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009570:Nitriles; D013004:Somatostatin; D014052:Toluidines; C065500:ASCL1 protein, human; C527525:teriflunomide; C517782:pasireotide; C535150:MAPK1 protein, human