As far as we know, the association of the stratification of GBM patients for drug synergism has not been attempted before in a sizeable set of GC cultures, and our finding that marker transcripts and mutations in EGFR and PIK3CA correlate with drug pair synergism in GBM can have important applications for the design of preclinical and clinical studies. This evidence concerns the gene PIK3CA and glioblastoma.