PID1 and medulloblastoma: Supporting the increased apoptosis in presence of PID1 + chemotherapy, siRNA-mediated PID1 knockdown had the opposite effect and diminished the cisplatin-induced apoptosis (AnnexinV binding, caspase-3 cleavage) and depolarization of mitochondrial membrane potential in UW228 medulloblastoma cells compared to cells treated with cisplatin + non-silencing control siRNA (Fig. 2; for PID1 protein level after siPID1 knockdown see Supplementary Fig. S3D).