H2AX and cancer: To corroborate the observed effects of IGPR-1 on the chemosensitivity of colon tumor cells, we measured phosphorylation of histone H2AX which is called γH2AX, an early biomarker of the cellular DNA damage response (DDR) to chemotherapeutic agents.42 DDR functions as an anti-cancer response and is an attempt to suppress tumor cell growth by inducing cell death or replicative cellular senescence.