Several compounds known to inhibit the growth of Sarcoma 180 were compared for their cytocidal activity in vivo. Standard inocula from donor mice which were treated with massive doses of the drugs were transplanted at 4 and 24 hours after treatment into untreated recipient animals. Viability was evaluated by cell counts and survival time. The effectiveness of triethylenethiophosphoramide and actinomycin D was in contrast to the lack of effect of amethopterin and 6-mercaptopurine. Azaserine, 6-diazo-5-oxo-l-norleucine, 6-methylpurine, N-methylformamide, 5-fluorouracil, and purine riboside had various degrees of activity. The viability test used can uncover some of the limitations of tumor-inhibitory compounds. Some of the reasons underlying such limitations are discussed. The importance of identifying compounds with cytocidal potentiality is emphasized.


This investigation was supported in part by a research grant (CY-2857) from the National Cancer Institute of the United States Public Health Service, and by a National Science Foundation Training Grant.

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