METB-06THE GLYCOLYSIS ENZYME GLUCOSE 6-PHOSPHATE ISOMERASE (GPI) STIMULATES GLIOBLASTOMA CELL MOTILITY IN AN AUTOCRINE FASHION

The Warburg effect describes the metabolic redirection in tumor cells away from oxidative phosphorylation to aerobic glycolysis, a status even enhanced by hypoxia. We recently discovered an oxygen concentration-dependent reciprocal metabolic switch between glycolysis and the pentose phosphate pathway, which is associated with a pro-migratory as opposed to a pro-proliferative phenotype, respectively (Kathagen et al., Acta Neuropathol 2013). However, the mechanistic link between glycolysis and cell migration is poorly understood. Since the hypoxia-induced glycolytic enzyme glucose 6-phosphate isomerase (GPI) is identical to autocrine motility factor (AMF), a secreted cytokine that binds to the cell surface receptor AMFR, we studied the functional effects of GPI/AMF on glioblastoma cells. Recombinant GPI/AMF strongly stimulated the migration of glioblastoma stem-like (GS) cells in modified Boyden chamber assays and was even more powerful than Hepatocyte Growth Factor/Scatter Factor, a known highly potent glioma cell motogen. In contrast, GPI/AMF moderately reduced the proliferation of GS cells. Erythrose 4-phosphate, an inhibitor of GPI/AMF activity, abrogated the pro-migratory effect of GPI/AMF while having no effect on GS cell proliferation. Gene expression profiling, qPCR and Western Blot analyses revealed a strong upregulation of GPI/AMF as well as of AMFR expression in response to hypoxia. Furthermore, the amount of secreted GPI/AMF in supernatants of GS cells was strikingly increased under hypoxia. GS cell-conditioned medium had a pro-migratory effect on cells, which was abrogated by immunodepletion of GPI/AMF from the culture medium. Knockdown of GPI/AMF expression by shRNA reduced GS cell migration but had no effect on proliferation. Immunostaining of human glioblastoma sections revealed increased expression of both GPI/AMF and AMFR in hypoxic pseudopalisading regions. To conclude, GPI/AMF is an extraordinarily potent motogen for GS cells, which explains in part the association between increased glycolytic activity. GPI/AMF may be thus be a valuable target for inhibiting glioblastoma cell invasion.