Mitogen-activated protein kinase (MEK/ERK) inhibition sensitizes cancer cells to centromere-associated protein E inhibition

Inhibition of centromere-associated protein-E (CENP-E) has demonstrated preclinical anti-tumor activity in a number of tumor types including neuroblastoma. A potent small molecule inhibitor of the Kinesin motor activity of CENP-E has recently been developed (GSK923295). To identify an effective drug combination strategy for GSK923295 in neuroblastoma, we performed a screen of siRNAs targeting a prioritized set of genes that function in therapeutically tractable signaling pathways. We found that siRNAs targeted to extracellular signal-related kinase 1 (ERK1) significantly sensitized neuroblastoma cells to GSK923295-induced growth inhibition (p = 0.01). Inhibition of ERK1 activity using pharmacologic inhibitors of mitogen-activated ERK kinase (MEK1/2) showed significant synergistic growth inhibitory activity when combined with GSK923295 in neuroblastoma, lung, pancreatic and colon carcinoma cell lines. Synergistic growth inhibitory activity of combined MEK/ERK and CENP-E inhibition was a result of increased mitotic arrest and Apoptosis. There was a significant correlation between ERK1/2 phosphorylation status in neuroblastoma cell lines and GSK923295 growth inhibitory activity (r = 0.823, p = 0.0006). Consistent with this result we found that lung Cancer cell lines harboring Ras mutations, which leads to oncogenic activation of MEK/ERK signaling, were significantly more resistant than cell lines with wild-type Ras to GSK923295-induced growth inhibition (p = 0.047). Here we have identified (MEK/ERK) activity as a potential biomarker of relative GSK923295 sensitivity and have shown the synergistic effect of combinatorial MEK/ERK pathway and CENP-E inhibition across different Cancer cell types including neuroblastoma.