Despite many important advances in cancer chemotherapy, complete eradication of tumors is often prevented by the presence or development of resistance to treatment. One mechanism by which resistance can arise occurs when cellular enzymes prevent or repair cytotoxic DNA modifications introduced by therapeutic agents. Thus, previous studies have shown that the formation of one cytotoxic modification by chloroethylnitrosourea, a dC-dG cross-link, is prevented by O6-alkylguanine-DNA alkyltransferase; high cellular levels of this enzyme are associated with resistance. New data indicate that the presence of 3-methyladenine DNA glycosylase also contributes to resistance to chloroethylnitrosoureas. The studies described here will investigate the mechanism by which glycosylases cause this increase in resistance and determine whether it extends to other chloroethylating agents. Glycosylase will be purified from the cloned human gene (L. Samson et al., Proc. Natl. Acad. Sci. USA 88, 9127-9131, 1991). Then, using DNA substrates modified by [3H]CNU and our library of modified bases, we will determine which modified bases are released by this enzyme. This information will relate the biochemical action of the glycosylase to its protective effect and identify modifications which are potentially cytotoxic. More evidence as to which lesions are cytotoxic will be obtained by determining which modified bases are depleted in resistant glial cells. Knowledge of which lesions are cytotoxic can ultimately be used in the design of new antitumor agents that cause these modifications, and in monitoring the effects of known agents. As substrate bases are identified, they will be tested for their ability to inhibit glycosylase action in vitro. Analogs of these substrates will also be tested as inhibitors. Inhibition of the glycosylase will presumably increase the cytotoxicity of the haloethylnitrosoureas and related agents, and this effect will be tested on glycosylase-deficient E. coli carrying plasmids with the human glycosylase and on cultured glial cells which are known to be resistant to chloroethylnitrosourea and to have high glycosylase levels.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA044499-10
Application #
2458048
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Program Officer
Forry-Schaudies, Suzanne L
Project Start
1986-08-01
Project End
1999-10-01
Budget Start
1997-08-01
Budget End
1999-10-01
Support Year
10
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Pharmacology
Type
Schools of Medicine
DUNS #
660735098
City
Worcester
State
MA
Country
United States
Zip Code
01655
Li, Qiong; Wright, Stephen E; Matijasevic, Zdenka et al. (2003) The role of human alkyladenine glycosylase in cellular resistance to the chloroethylnitrosoureas. Carcinogenesis 24:589-93
Ludlum, D B; Li, Q; Matijasevic, Z (1999) Role of base excision repair in protecting cells from the toxicity of chloroethylnitrosoureas. IARC Sci Publ :271-7
Ludlum, D B (1997) The chloroethylnitrosoureas: sensitivity and resistance to cancer chemotherapy at the molecular level. Cancer Invest 15:588-98
Matijasevic, Z; Boosalis, M; Mackay, W et al. (1993) Protection against chloroethylnitrosourea cytotoxicity by eukaryotic 3-methyladenine DNA glycosylase. Proc Natl Acad Sci U S A 90:11855-9
Niu, T; Yu, D; Kirk, M C et al. (1993) Synthesis of the prototype DNA-protein cross-link, 1-(guan-1-yl)-2-(cysteine-S-yl)ethane, and its role in the reactions of the haloethylnitrosoureas. Carcinogenesis 14:195-8
Matijasevic, Z; Sekiguchi, M; Ludlum, D B (1992) Release of N2,3-ethenoguanine from chloroacetaldehyde-treated DNA by Escherichia coli 3-methyladenine DNA glycosylase II. Proc Natl Acad Sci U S A 89:9331-4
Ludlum, D B; Habraken, Y; Carter, C A et al. (1992) The formation and enzymatic repair of DNA modifications caused by the haloethylnitrosoureas and related compounds. Nucleic Acids Symp Ser :25-6
Gonzaga, P E; Potter, P M; Niu, T Q et al. (1992) Identification of the cross-link between human O6-methylguanine-DNA methyltransferase and chloroethylnitrosourea-treated DNA. Cancer Res 52:6052-8
Matijasevic, Z; Bodell, W J; Ludlum, D B (1991) 3-Methyladenine DNA glycosylase activity in a glial cell line sensitive to the haloethylnitrosoureas in comparison with a resistant cell line. Cancer Res 51:1568-70
Habraken, Y; Carter, C A; Kirk, M C et al. (1991) Release of 7-alkylguanines from N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea-modified DNA by 3-methyladenine DNA glycosylase II. Cancer Res 51:499-503

Showing the most recent 10 out of 19 publications