Pertussis Toxin Is a Robust and Selective Inhibitor of High Grade Glioma Cell Migration and Invasion

Abstract

In high grade glioma (HGG), extensive tumor cell infiltration of normal brain typically precludes identifying effective margins for surgical resection or irradiation. Pertussis toxin (PT) is a multimeric complex that inactivates diverse Gi/o G-protein coupled receptors (GPCRs). Despite the broad continuum of regulatory events controlled by GPCRs, PT may be applicable as a therapeutic. We have shown that the urokinase receptor (uPAR) is a major driver of HGG cell migration. uPAR-initiated cell-signaling requires a Gi/o GPCR, N-formyl Peptide Receptor 2 (FPR2), as an essential co-receptor and is thus, PT-sensitive. Herein, we show that PT robustly inhibits migration of three separate HGG-like cell lines that express a mutated form of the EGF Receptor (EGFR), EGFRvIII, which is constitutively active. PT also almost completely blocked the ability of HGG cells to invade Matrigel. In the equivalent concentration range (0.01–1.0 μg/mL), PT had no effect on cell survival and only affected proliferation of one cell line. Neutralization of EGFRvIII expression in HGG cells, which is known to activate uPAR-initiated cell-signaling, promoted HGG cell migration. The increase in HGG cell migration, induced by EGFRvIII neutralization, was entirely blocked by silencing FPR2 gene expression or by treating the cells with PT. When U87MG HGG cells were cultured as suspended neurospheres in serum-free, growth factor-supplemented medium, uPAR expression was increased. HGG cells isolated from neurospheres migrated through Transwell membranes without loss of cell contacts; this process was inhibited by PT by >90%. PT also inhibited expression of vimentin by HGG cells; vimentin is associated with epithelial-mesenchymal transition and worsened prognosis. We conclude that PT may function as a selective inhibitor of HGG cell migration and invasion.