H2AX and cancer: To investigate the role of SUV39H2 in human cancer and the relationship between SUV39H2 and γ-H2AX, we examined the effect of SUV39H2 knockdown on radio- and chemosensitivity of cancer cells, because γ-H2AX is considered as a key regulator of the DNA repair system after DSBs, which causes chemo/radio-resistance of cancer cells6.