INHIBITORY EFFECT OF CARCINOSTATIC AGENTS ON ANTITUMOR ACTIVITY OF SENSITIZED LYMPHOID CELLS

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Effect of several carcinostatic agents on the antitumor activity of sensitized lymphoid cells obtained from Donryu rats immunized with Yoshida sarcoma was examined. The sensitized lymphoid cells were treated with various concentrations of a carcinostatic agent at 37° for 30 minutes. The washed cells were transferred with Yoshida sarcoma cells into recipient animals. The minimum effective concentration (A) of the agent to the sensitized peritoneal exudate cells was defined as the concentration which abolished the antitumor activity of the sensitized peritoneal exudate cells as determined by the death of the recipient animals by the tumor. The minimum effective concentration (B) of the agent to Yoshida sarcoma was examined in a similar manner as above and was defined as the lowest concentration of the agent which protected the recipient animals from death by the tumor.
A and B of each carcinostatic agent in mM were respectively as follows: Nitrogen mustard 0.008 and 0.001, Mitomycin-C 0.05 and 0.01, Actinomycin-D 0.001 and and 0.001, thio-TEPA 1.0 and 0.5, compound No. 838 1.0 and 1.0, and (2-chloroethyl) diethylamine 1.0 and >10. Puromycin and 6-mercaptopurine were ineffective on these cells in the present system. Antitumor activities of sensitized lymph-node cells and spleen cells were also abolished by the same concentration of Actiomycin-D as for the peritoneal exudate cells.
In vitro culture of Yoshida sarcoma cells mixed with sensitized peritoneal exudate cells resulted in a rapid decrease of the tumor cells, whereas cytocidal activity of the peritoneal exudate cells was inhibited by pretreatment of the cells with effective concentration of the carcinostatic agents.
Based on these results possible mechanism for the antitumor effect of sensitized lymphoid cells was discussed.