Additionally, integrin αvβ5 (ITGαvβ5) is highly expressed as a key receptor for OPN on tumor-infiltrating microglia, and the binding of both mediates the recruitment of glioma cells to microglia and polarization to the M2 phenotype, and reduces the direct cytotoxic sensitivity of tumors to CD8+ T cells (166). This evidence concerns the gene SPP1 and central nervous system cancer.