Many cancers, in particular, lymphomas, melanoma, mesothelioma, and hepatocellular, renal cell, and prostate carcinomas that are otherwise chemoresistant and with poor clinical outcome, exhibit decreased expression of arginine metabolizing enzymes including argininosuccinate synthetase (ASS1) and/or ornithine transcarbamylase (OTC) and are thus auxotrophic for arginine (74). The gene discussed is OTC; the disease is melanoma.