TSPO and glioblastoma: Classic TSPO ligands, such as PK11195, have demonstrated anticancer effects both in vitro and in vivo; in addition, newly synthesized TSPO ligands triggered apoptosis in human and rat GBM cells by modulating the opening of the mitochondrial permeability transition pore (MPTP), of which TSPO is an important constitutive protein [20, 21].