CD8A and cancer: By activating the GABAB receptor, GABA inhibits GSK-3β activity, which enhances β-catenin signaling, promoting cancer cell proliferation while suppressing intratumoral infiltration of CD8+ T cells.79 Furthermore, elimination of glutaminase, a vital enzyme for glutamine metabolism, within tumor cells stimulates T-cell activation and augments the efficacy of antitumor immune responses.