CPS1 and hepatocellular carcinoma: In addition, CTC staining with combined antibodies of P-CK and carbamoyl phosphate synthetase 1 (CPS1), a newly identified antigen for Hep Par 1 [119], were detected in 24 out of 27 (89%) patients with HCC, so this provided a better CTC detection method with an average of 20% that was consistently achieved compared to single-antibody-based method [30].