Improvement of the therapeutic efficacy of fluoropyrimidines in breast cancer is the main goal of this application. 5-FU is one of the most active drugs used in combination chemotherapy of metastatic breast and GI carcinoma. To increase the limited therapeutic index of FU, newly found differences between tumor and normal tissue in the disposition of uridine will be exploited. Specifically, differences in the Na+-dependent uridine transporter, which may be deficient in human tumors, and uridine phosphorylase, for which a BAU-insensitive activity may be selectively found in tumors, will be pursued. Both of these actions would tend to lead to lower levels of uridine in tumor vs normal cells; since uridine has been shown to protect against FU cytotoxicity, under the appropriate conditions a selective protection of normal tissue could be achieved without compromising the antitumor effect of FU. Were this to occur, the dose of FU could then be safely escalated. To evaluate differences in the uridine transporter between normal and neoplastic tissues, the applicant will measure expression of the transporter using a cDNA probe for the rabbit kidney Na+-dependent uridine transporter and another cDNA probe for a nucleoside transporter from rat intestinal epithelium; he will also attempt to clone and characterize the cDNA for the human gene from a human kidney cDNA library. He will generate antibodies against the transporter protein to probe surgical specimens for loss of this concentrative mechanism for uridine. To further pursue his observation that as much as 50% of uridine phosphorylase activity in selected human tumors is not sensitive to BAU, a potent inhibitor of uridine phosphorylase, the applicant will purify the non-BAU sensitive form of uridine phosphorylase; kinetically characterize differences in the catalytic activity of the enzymes from normal and neoplastic human tissue specimens; complete the cloning of the cDNA for the enzyme and prepare antibodies to the proteins; assess expression in human tumors and normal tissues; and initiate structural characterization of the enzyme by defining the binding domain for BAU utilizing photoaffinity or covalent labeling probes.
In specific aim 3, the applicant will continue his preclinical and clinical evaluation of BAU in a human breast cancer xenograft model and in a Phase I-II trial to determine if the MTD of FU can be raised by a BAU regimen that has been demonstrated to cause target changes in plasma uridine levels.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA067035-03
Application #
2683600
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Program Officer
Xie, Heng
Project Start
1996-04-01
Project End
2000-03-31
Budget Start
1998-04-01
Budget End
2000-03-31
Support Year
3
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Yale University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Wan, Laxiang; Cao, Deliang; Zeng, Jianmin et al. (2006) Modulation of uridine phosphorylase gene expression by tumor necrosis factor-alpha enhances the antiproliferative activity of the capecitabine intermediate 5'-deoxy-5-fluorouridine in breast cancer cells. Mol Pharmacol 69:1389-95
Cao, Deliang; Leffert, Janine J; McCabe, James et al. (2005) Abnormalities in uridine homeostatic regulation and pyrimidine nucleotide metabolism as a consequence of the deletion of the uridine phosphorylase gene. J Biol Chem 280:21169-75
Pizzorno, Giuseppe; Cao, Deliang; Leffert, Janine J et al. (2002) Homeostatic control of uridine and the role of uridine phosphorylase: a biological and clinical update. Biochim Biophys Acta 1587:133-44
Cao, Deliang; Russell, Rosalind L; Zhang, Dekai et al. (2002) Uridine phosphorylase (-/-) murine embryonic stem cells clarify the key role of this enzyme in the regulation of the pyrimidine salvage pathway and in the activation of fluoropyrimidines. Cancer Res 62:2313-7
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Pizzorno, G; Yee, L; Burtness, B A et al. (1998) Phase I clinical and pharmacological studies of benzylacyclouridine, a uridine phosphorylase inhibitor. Clin Cancer Res 4:1165-75