JAK1 and glioblastoma: To identify the kinase that phosphorylates PKM2 pS222, we pretreated U251 cells with a panel of inhibitors of multiple signal pathways reported to be activated upon DNA damage, such as ATM/DNA‐PK inhibitor (Torin2) and the inhibitors of EGFR signaling frequently activated in glioblastoma, including EGFR inhibitor (Afatinib), PI3K inhibitor (LY294002), AKT1/2/3 inhibitor (MK‐2206), MEK1/2 inhibitor (U0126), JAK1/2 inhibitor (Ruxolitinib), NF‐κB inhibitor (BAY11‐7082), followed by the treatment of etoposide.