Updated project metadata. Glioblastoma (GBM) is the most aggressive form of astrocytoma and is difficult to diagnose at early stage. In this study, our goal is to find and validate biomarkers for GBM through serum proteome expression profiling, which would assist in the early diagnosis, and management of GBMs. In the discovery phase, we performed shotgun proteomics of control and GBM pooled serum samples using untargeted 4-plex iTRAQ (isobaric Tags for Relative and Absolute Quantitation) mass spectrometry to identify candidate biomarkers with differential abundance The two candidates, S100A8 and S100A9 were prioritized for verification based on their maximal abundance in GBM serum in our discovery phase.