Targeted inhibition of MEK1 by cobimetinib leads to differentiation and apoptosis in neuroblastoma cells

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. conclusion: collectively,our results provide evidence that cobimetinib,in combination with cis-ra,represents a feasible option to develop novel treatment strategies for refractory nb. © 2015 singh et al.