XRCC6 and hepatocellular carcinoma: To further characterize the effects of mutating the putative Ku70 phosphorylation sites on HCC development, we examined liver sections of Ku703A/3A mice with pathology verified HCC by immunohistochemistry (IHC) staining with the proliferation marker Ki67, DSB marker γH2AX, and free radical damage/reactive oxygen species (ROS) marker 8-oxoguanine (8-oxo-G).