GRM3 and central nervous system cancer: Taken together, our work as well as that of others leads us to our current working hypothesis in which overexpression of system Xc in gliomas increases intracellular glutathione (protecting cells from ROS-related stresses) and increases extracellular glutamate which then acts as a paracrine/autocrine trophic factor for glioma progression through stimulation of GRM3.