Changes in amino acid metabolism caused by 6-azauridine triacetate: relevance to cancer treatment.

6-Azauridine triacetate (6-AzUrd-TA) administration causes changes in amino acid metabolism both in experimental animals and in man. This effect is dose-related. Amino acid changes caused by 6-AzUrd-TA resemble those in inborn homocystinuria, beta-alaninemia, and hyperhistidinemia. Inhibition of certain enzymes using pyridoxal phosphate as a coenzyme appears to be the common denominator for these changes. There is supportive evidence suggesting that homocystinemia and thrombotic episodes, both caused by 6-AzUrd-TA, are related. These results also reveal that anticancer drugs other than amino acid analogs and amino acid-depleting enzymes may cause significant changes in amino acid metabolism. Their detection and correlation with the therapeutic or adverse effects can be used as an alternative method for studying the relevance of amino acid changes to the treatment of cancer.