Hippocampal cells and cerebrospinal fluid were obtained as described previously (34 (link)), homogenized in lysate buffer containing protease inhibitor and centrifuged at 8,000 g/min at 4°C for 10 min. Total protein was extracted from the resulting supernatant using a Protein Extraction kit (20021; Qiagen Sciences, Inc., Gaithersburg, MD, USA), according to the manufacturer's instructions. SDS assays were performed as described previously (35 (link)). For western blot analysis, primary antibodies anti-bax (1:1,000; ab32503), anti-Bcl-2 (1:1,000; ab194583), anti-caspase-3 (1:1,000; ab13847), anti-caspase-9 (1:1,000; ab18571), anti-p38 (1:1,000; ab31828), anti-ERK (1:1,000; ab176660), anti β-actin (1:1,000; ab8226; all Abcam; Cambridge, UK) were added to PVDF membranes (EMD Millipore) and incubated at 4°C overnight. Membranes were blocked in 5% skimmed milk for 1 h at 37°C and then incubated with HRP-conjugated goat anti-rabbit IgG mAb (PV-6001; ZSGB-BIO) for 24 h at 4°C. A Ventana Benchmark automated staining system was used to determine protein expression in tumor tissues (Olympus BX51; Olympus Corporation).