FADD and glioblastoma: Interestingly, on the background of inducing mitochondrial apoptosis in glioblastoma cells, costunolide and tomentosine also effectively activated caspase-8 [51], and DMAPT-D6 significantly activated the expression of death receptors DR3 and DR5 and adapter proteins FADD and TRADD [57,71], suggesting the ability of STLs to induce glioblastoma cell death also by intrinsic receptor-dependent apoptosis, although this effect of STLs is still poorly understood.