A few purine metabolic enzymes have been reported to be deregulated in HCC: e.g. up-regulations of a trifunctional enzyme GART (phosphoribosylglycinamide formyltransferase, phosphoribosylglycinamide synthetase, phosphoribosylaminoimidazole synthetase) (14) and a bifunctional enzyme ATIC (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase) (15) in the purine de novo biosynthesis pathway; and down-regulation of xanthine dehydrogenase (XDH) (16) in the purine degradation pathway. This evidence concerns the gene XDH and hepatocellular carcinoma.