DDR genes such as breast cancer susceptibility gene 1/2 (BRCA 1/2), ataxia-telangiectasia mutated (ATM), and BRCA1-associated protein 1 (BAP1) were identified germline or somatic inactivation in 63.5% biliary tract cancer patients (Chae et al., 2019a). Here, BAP1 is linked to biliary tract cancer.