UBQLN4 and esophageal squamous cell carcinoma: To do that, we transfected TE‐10 UBQLN4‐OV cells with UBB‐DDK and used anti‐DDK antibody to co‐immunoprecipitate endogenous ubiquitinated‐MRE11A DDK‐tagged and UBQLN4 in cisplatin‐treated ESCC cell lines in the presence of MG‐132.