S100A8 and glioblastoma: There was a significant high abundance of both peptides for S100A8 and S100A9 (Mean values for peptide I, II, III and IV in GBM: 6504.9,11311.7,14812.1,9071.5 pg/ml respectively) in GBM sera as compared to non-detectable values in control sera as measured by MRM thus verified the results of discovery phase (Fig. 3A,B).