<qa>  What is arginine not an essential amino acid for human adults or infants?Amino acid deprivation therapy is an effective means for the treatment of some forms of cancer. Recently it has been found that human hepatocellular carcinomas HCC cell lines appear to require arginine for growth. Arginine is not an essential amino acid for human adults or infants as it can be synthesized from citrulline for review see Rogers 1994. Therefore, selective elimination of arginine from the circulation may be a means of treating patients with metastatic melanoma or non resectable HCC. 