In this project, we investigated the influence of EGFR pathway alterations on the 65 invasion promoting proteins in GBM secretome. We measured the rationally selected proteins through selected reaction monitoring (SRM) targeted mass spectrometry using stable isotope labeled internal peptide standards to quantity proteins in the secretome from five GBM (U87) isogenic cell lines in which EGFR, EGFRvIII and/or PTEN are expressed in cell lines.