XRCC4 and esophageal squamous cell carcinoma: In order to further confirm the effect of UBQLN2 expression levels on the radiosensitivity of ESCC cells, the protein expression levels of RPA70, XRCC-2, XRCC-4, Ligase IV, Ku70, RAD51, and p-DNA-PKcs involved in the homologous recombination (HR) and nonhomologous DNA terminal junction (NHEJ) DNA repair pathways were detected by Western blotting.