C5AR1 and glioblastoma: The activation of the C5a–C5aR1 signaling axis on the glioblastoma cells increases the expression of ZEB1, a regulator of epithelial–mesenchymal transition (EMT), via the p38 MAPK pathway, promoting invasion/infiltration of glioblastoma cells into parenchymal brain tissue [103] (Figure 4).