The urea cycle is an important ammonia metabolism pathway in hepatocytes, which plays a role not only in preventing ammonia poisoning, but also connects the TCA cycle and is closely related to glucose metabolism, lipid metabolism, and amino acid metabolism.[42] We found in this study that CPS1, the rate‐limiting enzyme of the urea cycle, was significantly reduced or even absent in HCC tissues. This evidence concerns the gene CPS1 and hepatocellular carcinoma.