CDK4 and glioblastoma: According to our findings, it appears that mTORC2-mediated phosphorylation of FLNA is a primary event in GBM migration and invasion, even though FLNA can be phosphorylated by multiple protein kinases including cyclic AMP (cAMP)-dependent protein kinase (PKA), p90 ribosomal kinase (RSK), PAK1, cyclin D1/Cdk4 and PKCα [49–52].