Based on a novel strategy, the overall objective of the proposed research is to develop new, more highly efficacious and selective drug combinations for the treatment of cancer. Numerous anticancer agents are substrates for enzymes that are subject to feedback inhibition and this regulatory mechanism can limit the activation of these drugs. Our approach to this problem involves the use of compounds which can stimulate these drug activation reactions by antagonizing feedback inhibition. We have demonstrated that 5'-amino-5'-deoxythymidine (5'-dThd) can antagonize the feedback inhibition of thymidine kinase exerted by thymidine triphosphate (dTTP) and, thereby, strongly stimulate the phosphorylation of thymidine or iododeoxyuridine (IdUrd), a cytotoxic analog. In a variety of cancer cells 5'-AdThd produces a marked increase in the uptake and cytotoxicity of IdUrd. Importantly, however, in certain circumstances this approach may produce preferential stimulation of drug activation in the cancer as compared to the normal cells. A recently developed methodology for propagating normal human urothelial cells in vitro has facilitated the comparison of these cells with a series of human bladder cancer cells. The uptake and phosphorylation of IdUrd was markedly stimulated by 5'-AdThd in the neoplastic but not in the normal cells. Since this unusual preferential stimulation may provide the basis for developing more selective cancer chemotherapy, elucidation of the biochemical mechanisms which produce these differential effects is the primary aim of this research. Several alternative hypotheses which could account for this selectivity will be tested. These include: differences in the pool sizes of the feedback inhibitors; altered levels of thymidine kinase activity; changes in regulatory properties of the thymidine kinases; and interactions with other, primarily catabolic enzymes. Since 5'-AdThd potently stimulates the uptake of IdUrd into mouse P388 leukemia cells, and because in vivo testing of this chemotherapeutic approach is important, initial studies of this drug combination in BDF1 mice will also be carried out. The primary question is whether 5'-AdThd can increase the therapeutic index of IdUrd in this animal tumor.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA036823-02
Application #
3174399
Study Section
Experimental Therapeutics Subcommittee 2 (ET)
Project Start
1985-03-01
Project End
1988-02-29
Budget Start
1986-03-01
Budget End
1987-02-28
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Vazquez-Padua, M A; Kunugi, K; Risueno, C et al. (1989) Modulation of the feedback regulation of thymidine kinase activity by pH in 647V cells. Cancer Res 49:5644-9
Grem, J L; Mulcahy, R T; Miller, E M et al. (1989) Interaction of deoxyuridine with fluorouracil and dipyridamole in a human colon cancer cell line. Biochem Pharmacol 38:51-9
Vazquez-Padua, M A; Risueno, C; Fischer, P H (1989) Regulation of the activation of fluorodeoxyuridine by substrate competition and feedback inhibition in 647V cells. Cancer Res 49:618-24
Vazquez-Padua, M A; Fischer, P H; Christian, B J et al. (1989) Basis for the differential modulation of the uptake of 5-iododeoxyuridine by 5'-aminothymidine among various cell types. Cancer Res 49:2415-21
Vazquez-Padua, M A; Kunugi, K; Fischer, P H (1989) Enzyme regulatory site-directed drugs: study of the interactions of 5'-amino-2', 5'-dideoxythymidine (5'-AdThd) and thymidine triphosphate with thymidine kinase and the relationship to the stimulation of thymidine uptake by 5'-AdThd in 647V cells. Mol Pharmacol 35:98-104
Fischer, P H; Fang, T T; Lin, T S et al. (1988) Structure-activity analysis of antagonism of the feedback inhibition of thymidine kinase. Biochem Pharmacol 37:1293-8
Van Mouwerik, T J; Pangallo, C A; Willson, J K et al. (1987) Augmentation of methotrexate cytotoxicity in human colon cancer cells achieved through inhibition of thymidine salvage by dipyridamole. Biochem Pharmacol 36:809-14
Fischer, P H; Vazquez-Padua, M A; Reznikoff, C A et al. (1986) Preferential stimulation of iododeoxyuridine phosphorylation by 5'-aminothymidine in human bladder cancer cells in vitro. Cancer Res 46:4522-6
Fischer, P H; Vazquez-Padua, M A; Reznikoff, C A (1986) Perturbation of thymidine kinase regulation: a novel chemotherapeutic approach. Adv Enzyme Regul 25:21-34
Grem, J L; Fischer, P H (1986) Alteration of fluorouracil metabolism in human colon cancer cells by dipyridamole with a selective increase in fluorodeoxyuridine monophosphate levels. Cancer Res 46:6191-9

Showing the most recent 10 out of 12 publications