AKT1 and glioblastoma: Strikingly, there was a trend (P < 0.05) towards reduced phosphorylation of AKT and its downstream target cAMP response element-binding protein (CREB) in GBM of patients resistant to TMZ therapy while ERK activation remained unchanged on a high level (Fig. 1a and Additional file 1: Figure S1a) indicating a role of these kinase in resistance development.