GAD2 and neoplasm: In our present study, based on the transcriptomic analysis of OSCC tissues, GABAergic signaling was significantly downregulated overall following treatment with heat-killed P. intermedia. The expression of GABBR2, GABRB3, GABA-transaminase (ABAT), glutamate decarboxylase 2 (GAD2), and Slc6a11 (GAT3) was clearly suppressed in heat-killed P. intermedia-treated tumor tissues.