GAD1 and neoplasm: In U-87MG cell-derived tumours, immunostaining for mature neuronal markers, including tubulin beta 3 (TUBB3) and glutamate decarboxylase 1 (GAD1/GAD-67), involved in GABA synthesis, revealed high expression levels in si-hVDAC1-TTs and low expression in the NT-TTs (Figure 5A,B), as reported previously [21].