Many advanced human tumors more commonly associated with chemoresistance and poor clinical outcome, including hepatocellular carcinoma (HCC), melanoma, mesothelioma, pancreatic cancer, prostate cancer, renal cell carcinoma, sarcoma and small cell lung cancer, exhibit loss of ASS1 expression and are thus arginine auxotrophs [2–9]. This evidence concerns the gene ASS1 and hepatocellular carcinoma.