APOE and meningioma: For the meningioma CSF samples, three peptides of APOE (SELEEQLTPVAEETR, LGPLVEQGR and AATVGSLAGQPLQER) gave a cumulative fold change of 2.21 whereas peptides of PTGDS (WFSAGLASNSSWLR, TMLLQPAGSLGSYSYR and AQGFTEDTIVFLPQTDK) showed a fold change of 1.52 (Figures 2B, C).