CASP9 and central nervous system cancer: Our results (Fig. 2D) showed that after treated with PTE at different times, the apoptosis-related proteins such as cleaved caspase-3, cleaved caspase-9, cleaved PARP-1, and Bax increase significantly, while anti-apoptotic proteins Bcl-2 and Survivin reduced obviously, which further confirmed PTE induced glioma cell apoptosis may occur through the mitochondrial pathway with time-dependent characteristics.