H2AX and breast cancer: To explore the potential functions of nuclear PKM2 during DNA damage response (DDR), we previously performed immunoprecipitation-coupled liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) using anti-PKM2 antibody in human breast cancer cell line MCF7 and identified a number of nuclear proteins in DNA damage signaling as PKM2 binding partners, among which histone H2AX appeared (Figure 1A and 1B) [27].