CDK4 and glioblastoma: To elucidate the role of FOSL1 in response to TMZ, a DNA alkylating drug that induces cell cycle arrest in GBM cells, we analyzed the levels of FOSL1 and G0/G1 to S phase transition‐associated proteins, including CDK2, CDK4, cyclin D, and cyclin E29, in primary GBM cells with unmethylated (TMZ‐resistant group) or methylated MGMT (TMZ non‐resistant group).