We have demonstrated that S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) given to mice prior to ionizing radiation inhibits development of radiation-induced sarcomas. The right hind legs of C3Hf/Kam mice were exposed to single doses of γ-rays ranging from 3400 to 5700 rads. Thirty min before irradiation, approximately one-half of the mice were given i.p. injections of WR-2721 (400 mg/kg). Mice were checked for development of radiation-induced tumors within the irradiated tissue of legs from 250 up to 786 days after irradiation. Tumors first appeared in both groups of mice at approximately 300 days after irradiation. Thereafter, the rate of tumor development was slower in mice that received both WR-2721 and leg irradiation. At the end of the observation period, the overall actuarial tumor incidence in these mice was 26%, compared to 87% in mice exposed to radiation only. Since WR-2721 has the ability to protect against radiation carcinogenesis, it may also afford protection against the carcinogenic effect of alkylating agents.

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This investigation was supported in part by Grants CA-06294 and CA-16672, awarded by the National Cancer Institute, Department of Health and Human Services. Animals used in this study were maintained in facilities approved by the American Association for Accreditation of Laboratory Animal Care and in accordance with current regulations and standards of the United States Department of Agriculture and Department of Health and Human Services, NIH.

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