(2) Arginine metabolism: ASS1 is recognised as the rate-limiting enzyme in arginine synthesis, and in many cancers, including hepatocellular carcinoma, melanoma, prostate cancer, and renal cancer, ASS1 expression is downregulated or even absent, thus preventing cells from synthesising arginine and making them dependent on exogenous arginine. This evidence concerns the gene ASS1 and prostate carcinoma.