TACR1 and central nervous system cancer: SP activates the MAPK pathway, increasing ERK2 kinase activity and DNA synthesis in glioma cells, and EGFR is an essential regulator in SP/NK-1R-induced activation of the MAPK pathway and cell proliferation in U-373 MG glioma cells, and these events are mediated by subunit Gαi protein [47] (Figure 1).