title: Targeted inhibition of MEK1 by cobimetinib leads to differentiation and apoptosis in neuroblastoma cells.
abstract: BACKGROUND
  Neuroblastoma (NB) is one of the most common childhood malignancies. Currently, high risk NB carries a poor outcome and significant treatment related toxicities and, thus has been a focus for new therapeutics research in pediatric oncology. In this study, we evaluated the effects of the MEK inhibitor cobimetinib, as a single agent and in combinations, on the growth, survival and differentiation properties against a molecularly representative panel of NB cell lines.
  
  
  METHODS
  In vitro anti-proliferative activity of cobimetinib alone or in combination was investigated by cell viability assays and its target modulatory activity was evaluated using phospho-kinases antibody arrays and western blot analysis. To determine the effect of combination with cis-RA on differentiation and resulting enhanced cellular cytotoxicity, the expression of glial fibrillary acidic protein (GFAP) and microtubule-associated protein 2 (MAP2) expression levels were examined by immuno-fluorescence.
  
  
  RESULTS
  Our findings show that cobimetinib alone induced a concentration-dependent loss of cell viability in all NB cell lines. In addition, cobimetinib showed feedback activation of MEK1/2, and the dephosphorylation of extracellular signal-regulated kinases (ERK1/2) and c-RAF, providing information on the biological correlates of MEK inhibition in NB. Combined treatment with cis-RA, led to differentiation and enhanced sensitization of NB cells lines to cobimetinib.
  
  
  CONCLUSIONS
  Collectively, our results provide evidence that cobimetinib, in combination with cis-RA, represents a feasible option to develop novel treatment strategies for refractory NB.
authors.affiliation: POETIC Laboratory for Preclinical and Drug Discovery Studies, University of Calgary, Calgary, Alberta, Canada. asingh@ucalgary.ca.|Division of Pediatric Oncology, Alberta Children's Hospital, 2888 Shaganappi Trail NW, Calgary, Alberta, T3B 6A8, Canada. asingh@ucalgary.ca.
authors.forename: Anjali
authors.initials: A
authors.lastname: Singh
authors.affiliation: POETIC Laboratory for Preclinical and Drug Discovery Studies, University of Calgary, Calgary, Alberta, Canada. ruan@ucalgary.ca.|Division of Pediatric Oncology, Alberta Children's Hospital, 2888 Shaganappi Trail NW, Calgary, Alberta, T3B 6A8, Canada. ruan@ucalgary.ca.
authors.forename: Yibing
authors.initials: Y
authors.lastname: Ruan
authors.affiliation: Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA. trippet1@MSKCC.org.
authors.forename: Tanya
authors.initials: T
authors.lastname: Tippett
authors.affiliation: POETIC Laboratory for Preclinical and Drug Discovery Studies, University of Calgary, Calgary, Alberta, Canada. a.narendran@ucalgary.ca.|Division of Pediatric Oncology, Alberta Children's Hospital, 2888 Shaganappi Trail NW, Calgary, Alberta, T3B 6A8, Canada. a.narendran@ucalgary.ca.
authors.forename: Aru
authors.initials: A
authors.lastname: Narendran
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001384:Azetidines / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis; D006801:Humans; D015474:Isotretinoin / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D009447:Neuroblastoma / Q000188:drug therapy* / Q000473:pathology; D010880:Piperidines / Q000494:pharmacology*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism
chemical_list: D001384:Azetidines; D005904:Glial Fibrillary Acidic Protein; C489788:MAP2 protein, human; D008869:Microtubule-Associated Proteins; D010880:Piperidines; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D015474:Isotretinoin; C574276:cobimetinib