Aurora Kinase A Inhibition plus Tumor Treating Fields Suppress Glioma Cell Proliferation in a Cilium-Independent Manner

Abstract

Tumor Treating Fields (TTFields) have been shown to extend the survival of glioblastoma (GBM) patients. TTFields interfere with a broad range of cellular processes which may contribute to their efficacy. Among these, TTFields disrupt primary cilia stability on GBM cells. Here we asked if concomitant treatment of TTFields with other agents that interfere with GBM ciliogenesis can further suppress GBM cell proliferation in vitro. Aurora Kinase A (AURKA) promotes both cilia disassembly and GBM growth in vitro and in xenograft models. Inhibitors of AURKA such as Alisertib have been previously demonstrated to inhibit cilia disassembly and increase the frequency of cilia in various cell types. However, here we show that physiological concentrations of Alisertib treatment significantly reduced GBM cilia frequency in gliomaspheres across multiple patient derived cell lines, and in patient biopsies treated ex vivo with Alisertib. This activity of Alisertib seems to be glioma cell specific as it did not reduce neuronal or glial cilia frequencies in mixed primary cell cultures from mouse forebrain. Furthermore, Alisertib depletion of glioma cilia appears specific to AURKA inhibition, as a potent AURKB inhibitor, AZD1152, had no effect on GBM ciliary frequency. Treatment of two different GBM patient-derived cell lines with TTFields and Alisertib resulted in a significant reduction in cell proliferation compared to either treatment alone. However, this effect was not cilia-dependent as the combined treatment reduced proliferation in cilia-depleted cell lines lacking, ARL13b, or U87MG cells which are naturally devoid of ARL13B+ cilia. This result is not surprising given the wide range of pathways regulated by AURKA in addition to cilia. Nonetheless, Alisertib-mediated effects on glioma cilia may be a useful biomarker of drug efficacy within tumor tissue. Considering Alisertib has been shown to cross the blood brain barrier and inhibit intracranial growth of xenografted tumor models, our data warrant future studies to explore whether concomitant Alisertib and TTFields exposure prolongs survival of brain tumor-bearing animals in vivo.