CPS1 and liver cancer: Carbamoyl Phosphate Synthetase I (CPS1) is an enzyme found in the mitochondrion, responsible for catalyzing the first and rate-limiting step of the hepatic urea cycle, critical for the removal of excess urea from cells.7,8 There is evidence to suggest that CPS1 downregulation may play a critical role in the development of HCC in 5.92% of liver cancer cases according to TCGA.6,9,10