CA9 and cholangitis: Notably, in an early clinical trial to treat metastatic renal cell cancer with CAR-engineered T cells, with total T-cell doses as low as 2 × 108 T cells, we observed reversible yet discrete cholangitis and damage to bile duct epithelium as a likely consequence of T-cell localization and expression of the target epitope carbonic anhydrase IX (CAIX) on normal tissue [6].