H2AX and esophageal squamous cell carcinoma: To further understand whether KDMs activity inhibition with IOX1 treatment affects DNA damage repair (DDR), enriched γ-H2AX foci were found after 0.5 h 2 Gy IR until 24 h in all ESCC cells treated with IOX1, under hypoxic conditions (50 μM CoCl2 and 0.5–1% O2), indicating increased DSBs and less DDR (Fig. 5a).