Enzymes of purine metabolism in cancer.

In cancer cells, a marked imbalance in the enzymic pattern of purine metabolism is linked with transformation and/or progression. In chemically-induced, transplantable hepatomas in rat, the specific activities of the anabolic enzymes, IMP dehydrogenase, GMP synthetase, adenylosuccinate synthetase, adenylosuccinase, AMP deaminase and amidophosphoribosyltransferase, increased to 13.5-, 3.7-, 3.1-, 1.8-, 5.5- and 2.8-fold, respectively, of those in normal liver. Activities of the catabolic enzymes, inosine phosphorylase, xanthine oxidase and uricase, decreased to 19, 10 and 4%, respectively. This enzymic imbalance was specific to hepatic neoplasia, since no similar pattern was observed in differentiating or regenerating liver. Most enzymic alterations were present also in chemically- and virus-induced animal tumors, in human kidney, liver and colon carcinomas, and in human colon carcinoma xenografts. The molecular correlation concept applies to purine biochemistry and an important segment of neoplastic gene expression was identified in the behavior of key purine-metabolizing enzymes.