ATM and hepatocellular carcinoma: Recently, PKM2 was found to be phosphorylated on T328 by GSK-3β and this phosphorylation was critical for the stability and biological function of PKM2 in hepatocellular carcinoma.43 GSK3β is a cytoplasmic-nuclear shuttling protein that is active in the nucleus following DNA damage.44 Therefore, we cannot rule out that in addition to ATM, GSK3β may also phosphorylate nuclear PKM2 in response to DNA damage.