This proposal focuses on the biological consequence of purine starvation in order to elucidate the mechanism of the antitumor effects of purine antimetabolites. These agents cause either general purine starvation or selective depletion of adenine or guanine alone. We have found that each class of purine depleting agents produces distinct biological effects, most notably the dramatic inhibition of DNA synthesis that occurs with guanine starvation. One portion of the project proposal deals with the interaction among the cellular toxicities caused by combined or individual adenine and guanine starvation in order to provide a biochemical rationale for the selection of purine antimetabolites as anticancer agents. The other portion addresses specifically the effects of guanine depletion alone. Inhibitors of de novo guanine nucleotide formation (via IMP dehydrogenase) rank among the most potent antiviral and antitumor agents. Yet it remains unknown why ribavirin for example is a potent antiviral agent with rather poor antitumor efficacy, while tiazofurine is a potent antitumor drug, at least in animal models. The toxicity of both agents can be reversed by the addition of a guanine source via the salvage bypass, which suggests that guanine starvation is indeed the major mode of action. Howeve, we have observed differences in the biochemical mechanism of action of these agents that may result from differential effect on guanine nucleotide metabolism. Indeed, GMP, GDP and GTP each serve different cellular functions, with GDP possibly representing the functional DNA precursor pool that feeds into the """"""""replitase"""""""" system. The replitase is thought to be a multienzyme complex that utilizes distant DNA precursors and channels substrates directly to the site of replication forks. The proposal thus presents a novel approach to study the mechanism of the cellular toxicity of guanine depleting agents, that takes into account the possible compartmentation of guanine nucleotides (mono-, di and tri-phosphates) into general cellular pools and functional pools for specific purposes.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA027866-05
Application #
3167872
Study Section
Experimental Therapeutics Subcommittee 2 (ET)
Project Start
1981-07-01
Project End
1987-06-30
Budget Start
1985-07-01
Budget End
1986-06-30
Support Year
5
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Pharmacy
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Duan, D S; Smith, W; Sadee, W et al. (1992) Characterization of three T-lymphoid cell lines with distinct sensitivities to deoxyadenosine plus deoxycoformycin. Thymus 19:1-11
Duan, D S; Nagashima, T; Hoshino, T et al. (1990) Mechanisms of 2'-deoxyguanosine toxicity in mouse T-lymphoma cells with purine nucleoside phosphorylase deficiency and resistance to inhibition of ribonucleotide reductase by dGTP. Biochem J 268:725-31
Cheng, H W; Armstrong, R D; Sadee, W (1988) Modulation of 6-thioguanine activity by guanine in human promyelocytic leukemia HL-60 cells. Cancer Res 48:3648-51
Yu, V C; Hochhaus, G; Chang, F H et al. (1988) Differentiation of human neuroblastoma cells: marked potentiation of prostaglandin E-stimulated accumulation of cyclic AMP by retinoic acid. J Neurochem 51:1892-9
Duan, D S; Sadee, W (1988) Guanine for DNA synthesis. A compulsory route through ribonucleotide reductase. Biochem J 255:1045-8
Preis, P N; Saya, H; Nadasdi, L et al. (1988) Neuronal cell differentiation of human neuroblastoma cells by retinoic acid plus herbimycin A. Cancer Res 48:6530-4
Duan, D S; Sadee, W (1987) Distinct effects of adenine and guanine starvation on DNA synthesis associated with different pool sizes of nucleotide precursors. Cancer Res 47:4047-51
Sadee, W; Yu, V C; Richards, M L et al. (1987) Expression of neurotransmitter receptors and myc protooncogenes in subclones of a human neuroblastoma cell line. Cancer Res 47:5207-12
Pawlak, K; Lawi-Berger, C; Sadee, W (1986) Incorporation of nucleotide tracers into nucleic acids in permeabilized cells and cellular homogenates. Biochem J 238:13-21
Nguyen, B T; Sadee, W (1986) Compartmentation of guanine nucleotide precursors for DNA synthesis. Biochem J 234:263-9

Showing the most recent 10 out of 12 publications