Down regulation of argininosuccinate synthetase (ASS), which synthesizes arginine from citrulline, is associated with cancers including melanoma, hepatocellular carcinoma, prostate carcinoma, lung & colon carcinomas, sarcomas, invasive breast carcinoma, and renal cell carcinoma (20–22). Here, ASS1 is linked to hereditary clear cell renal cell carcinoma.