""""""""Tumor Cell Hypoxia as a Factor in Cancer Therapy"""""""" is a long range project aimed at promoting a more quantitative analysis of factors that affect the radiation response of mammalian cells. The central theme for the proposed studies is to investigate the basic mechanisms of action for hypothermia, electron-affinic radiosensitizers, and radiation, to define the interactions between these three treatment modalities at the cellular and molecular level, and to utilize this information for optimizing treatment strategies for cancers. Using a variety of in vivo and in vitro procedures (colony assay, serial dilution assay, 125 I-iododeoxyuridine prelabeling technique), an attempt will be made to evaluate the importance of the oxygen effect in radiation therapy of cancers. Specifically, the effects of three classes of electron-affinic agents (nitroimidazoles, benzotriazines, quinones) will be investigated on euoxic and hypoxic cancer cells at normal (37 degrees Celsius) and elevated (41.5 degrees Celsius) incubation temperatures. We have previously demonstrated that exposure of tumors to physiologically tolerable doses of nitroimidazoles (misonidazole, metronidazole) alone or hyperthermia alone produces only modest radiosensitization (enhancement ratio up to 2.0). However, combined administration of hyperthermal and nitroimidazoles induces very pronounced, synergistic radiosensitization effects with enhancement ratios of 4.3 or higher. This ratio is considerably better than the 3-fold sensitization that could be achieved by full oxygenation of previously hypoxic tumors. Since identical combination treatment produces only modes or no radiosensitization of normal body tissues, the proposed treatment regimen could produce a large therapeutic gain factor in cancer radiation therapy. The immediate goal is to extend this work to newly developed electron- affinic agents, to further investigate the cellular and molecular mechanisms responsible for synergistic radiosensitization (dose modification, repair inhibition, additive damage interactions), to evaluate the mechanisms responsible for direct cytocidal effects of hyperthermia and electron-affinic agents, and to obtain additional information on environmental and intracellular factors which govern the magnitude of these effects. As part of this project, ongoing radionuclide suicide studies with iodine-125 and other Auger emitting radionuclides will be continued.
The aim of these studies is to explore the fundamental mechanism(s) for radiation-induced cell death and to utilize the unique decay properties of Auger emitters for selective radionuclide therapy of cancers.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA021673-10A2
Application #
3165616
Study Section
Radiation Study Section (RAD)
Project Start
1978-08-01
Project End
1994-11-30
Budget Start
1989-12-01
Budget End
1990-11-30
Support Year
10
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Florida State University
Department
Type
Schools of Arts and Sciences
DUNS #
020520466
City
Tallahassee
State
FL
Country
United States
Zip Code
32306
Hofer, K G; Lin, X; Bao, S (1996) DNA damage, micronucleus formation, and cell death from 125I decays in DNA. Acta Oncol 35:825-32
Hofer, K G (1996) Biophysical aspects of Auger processes--A review. Acta Oncol 35:789-96
Ludwikow, G; Hofer, K G; Bao, S P et al. (1996) The effect of 125I decay at different stages of S-phase on survival, expression of micronuclei and chromosome aberrations in CHO cells. Int J Radiat Biol 70:177-87
Hofer, K G; Bao, S P (1995) Low-LET and high-LET radiation action of 125I decays in DNA: effect of cysteamine on micronucleus formation and cell killing. Radiat Res 141:183-92
Charlton, D E; Hofer, K G; Vanloon, N et al. (1994) Double-strand breaks from 125I incorporated in the DNA and cell death. Int J Radiat Biol 66:437-40
Hofer, K G; van Loon, N; Schneiderman, M H et al. (1993) Targets for radiation-induced cell death: target replication during the cell cycle evaluated in cells exposed to X-rays or 125I decays. Int J Radiat Biol 64:205-16
Hofer, K G; van Loon, N; Schneiderman, M H et al. (1992) The paradoxical nature of DNA damage and cell death induced by 125I decay. Radiat Res 130:121-4
Schneiderman, M H; Hofer, K G; Schneiderman, G S (1991) An in vitro 125IUdR-release assay for measuring the kinetics of cell death. Int J Radiat Biol 59:397-408
Schneiderman, M H; Hofer, K G; Schneiderman, G S (1990) Association between the division delay target and DNA late in the cell cycle. Radiat Res 122:337-40
Hofer, K G; Lakkis, M; Hofer, M G (1989) Cytocidal effects of misonidazole, Ro 03-8799, and RSU-1164 on euoxic and hypoxic BP-8 murine sarcoma cells at normal and elevated temperatures. Cancer 63:1501-8

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