Macrophage migration inhibitory factor promotes vasculogenic mimicry formation induced by hypoxia via CXCR4/AKT/EMT pathway in human glioblastoma cells

Macrophage migration inhibitory factor (MIF) is over-expressed and secreted in various cancer cells in particular in response to hypoxia. Recent studies have shown that, under hypoxic conditions, glioblastoma (GBM) cells display the ability to drive blood-perfused vasculogenic mimicry (VM). The aim of this study was to investigate the underlying mechanism of MIF in the regulation of hypoxia-induced VM in GBM cells. By analyzing clinical specimens, we observed the co-localization of MIF, C-X-C motif chemokine receptor 4 (CXCR4) and VM in hypoxic regions of gliomas. In vitro, the exposure of GBM cells (U87 and U251) to hypoxia increased the expression of MIF and CXCR4 and induced VMs. Other data demonstrated that ectogenic rhMIF promoted VMs in GBM cells and knock-down endogenous MIF attenuated hypoxia-induced VMs. In addition, we demonstrated that MIF augmented VM formation ability by enhancing the epithelial mesenchymal transition (EMT) through the CXCR4-AKT pathway. Moreover, in vivo, the subcutaneous injection of rhMIF resulted in the progression of EMT and VMs formation. On the contrary, CXCR4-AKT pathway inhibitors blocked the effects of rhMIF on EMT and VMs formation. Collectively, our results support a critical role for the MIF-CXCR4 signaling axis in regulating hypoxia-induced VMs formation, indicating the potential usefulness of MIF as a notable target for the anti-vascularization treatment of GBM.