The mechanisms by which ionizing radiations exert their effects on mammalian cells and tissues, and the mechanisms by which endogenous or exogenous thiol compounds, or indeed radiomodifying agents in general, modulate these damaging effects are very poorly understood. It is the purpose of this study to further our understanding of these processes by investigating the effects of carefully selected thiols on the DNA-damaging and lethal effects of radiation in vitro. We propose to develop a detailed understanding of the relative effects of these selected compounds on survival and on various endpoints for damage to genomic DNA of oxic and hypoxic cells. These studies will utilize a series of DNA repair-deficient mutant mammalian cell lines in order to address the hypothesis that cell death may not always result from the induction and repair of a specific """"""""lethal lesion"""""""", but rather that, depending on the particular combination of genetic and redox factors, the lethal effects of different classes of DNA lesions may be differently expressed. In addition to exogenous thiols, we will also examine the effects of modifying the redox status of these cells lines by varying oxygen and glutathione levels and examining the associated effect on these relationships between DNA or chromosome damage and cell survival as exogenous thiol levels are altered. Through the understanding of the mechanism of action of radiomodifying compounds and its dependence on their structure, we will ultimately be able to place the rationale for the selection and development of radiomodifying agents on a logical mechanistic basis. Similarly, by examining the correlations between the effects of these radiomodifiers on the relationships between various types of DNA or chromosome damage and cell survival we will be able to shed light on the very basic mechanisms of radiation lethality. These data will also provide a foundation for future studies examining the relationships between stem/target cell survival and DNA or chromosome damage induction and repair processes in vivo.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29CA049477-04
Application #
3459349
Study Section
Radiation Study Section (RAD)
Project Start
1989-12-01
Project End
1993-07-16
Budget Start
1992-12-01
Budget End
1993-07-16
Support Year
4
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Type
Other Domestic Higher Education
DUNS #
001910777
City
Houston
State
TX
Country
United States
Zip Code
77030
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Sestili, P; Cantoni, O; Cattabeni, F et al. (1995) Evidence for separate mechanisms of cytotoxicity in mammalian cells treated with hydrogen peroxide in the absence or presence of L-histidine. Biochim Biophys Acta 1268:130-6
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Murray, D; Prager, A; Altschuler, E M et al. (1991) Effect of thiols on micronucleus frequency in gamma-irradiated mammalian cells. Mutat Res 247:167-73