IRF1 and glioblastoma: Furthermore, PTEN-deficient GBM cells activate the PI3K/AKT pathway, which suppresses interferon regulatory factor 1 (IRF1) degradation by phosphorylating glycogen synthase kinase 3 beta (GSK3β) into its inactive form, with higher levels of IRF1, inducing Gal-9 transcription (Figure 2).