Differential expression of uridine phosphorylase in tumors contributes to an improved fluoropyrimidine therapeutic activity.

Abstract

Abrogation of uridine phosphorylase (UPase) leads to abnormalities in pyrimidine metabolism and host protection against 5-fluorouracil (5-FU) toxicity. We elucidated the effects on the metabolism and antitumor efficacy of 5-FU and capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) in our UPase knockout (UPase(-/-)) model. Treatment with 5-FU (85 mg/kg) or capecitabine (1,000 mg/kg) five days a week for four weeks caused severe toxicity and structural damage to the intestines of wild-type (WT) mice, but not in UPase(-/-) animals. Capecitabine treatment resulted in a 70% decrease in blood cell counts of WT animals, with only a marginal effect in UPase(-/-) mice. UPase expressing colon 38 tumors implanted in UPase(-/-) mice revealed an improved therapeutic efficacy when treated with 5-FU and capecitabine because of the higher maximum tolerated dose for fluoropyrimidines achievable in UPase(-/-) mice. (19)F-MRS evaluation of capecitabine metabolism in tumors revealed similar activation of the prodrug in UPase(-/-) mice compared with WT. In WT mice, approximately 60% of capecitabine was transformed over three hours into its active metabolites, whereas 80% was transformed in tumors implanted in UPase(-/-) mice. In UPase(-/-) mice, prolonged retention of 5'dFUR allowed a proportional increase in tumor tissue. The similar presence of fluorinated catabolic species confirms that dihydropyrimidine dehydrogenase activity was not altered in UPase(-/-) mice. Overall, these results indicate the importance of UPase in the activation of fluoropyrimidines, the effect of uridine in protecting normal tissues, and the role for tumor-specific modulation of the phosphorolytic activity in 5-FU or capecitabine-based chemotherapy.

• Authors: Deliang Cao, Amy Ziemba, James McCabe, Ruilan Yan, Laxiang Wan, Bradford Kim, Michael Gach, Stuart Flynn, Giuseppe Pizzorno
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 10 Issue 12 Pg. 2330-9 (Dec 2011) ISSN: 1538-8514 [Electronic] United States
• PMID: 21954436 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Antimetabolites, Antineoplastic
• Prodrugs
• Pyrimidines
• Deoxycytidine
• Capecitabine
• Uridine Phosphorylase
• Fluorouracil

Topics

• Animals
• Antimetabolites, Antineoplastic (metabolism, therapeutic use)
• Capecitabine
• Cell Line, Tumor
• Deoxycytidine (analogs & derivatives, therapeutic use)
• Drug Evaluation, Preclinical
• Drug Resistance, Neoplasm (genetics)
• Fluorouracil (analogs & derivatives, metabolism, therapeutic use)
• Gene Expression Regulation, Enzymologic (drug effects, physiology)
• Gene Expression Regulation, Neoplastic (drug effects, physiology)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Neoplasms (drug therapy, enzymology, genetics, metabolism)
• Prodrugs (metabolism, therapeutic use)
• Pyrimidines (metabolism, therapeutic use)
• Treatment Outcome
• Uridine Phosphorylase (genetics, metabolism, physiology)