DKK1 and biliary tract neoplasm: DKN-01, an anti-DKK1 mAb, could block the immunosuppressive effects of DKK1 in the tumor microenvironment (TME) (Haas et al., 2021) and also perform potential antiangiogenic and immunomodulatory activity in combination therapy with gemcitabine/cisplatin in advanced biliary tract cancer (Goyal et al., 2020).