GSR and cancer: Among the different metabotropic- (mGluR) and ionotropic- (iGluR) glutamate receptors (GluR), the iGluRs belonging to N-methyl-D-aspartate receptor (NMDAR) family are gaining importance as targets in cancer, primarily due to their ability to stimulate mTOR- and ERK-signaling pathways that could be correlated with cell survival and proliferation [35,36,37].