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Lymphadenosis NK/LY resistant to rubomycin was obtained on its repeated cultivation in mice treated with the antibiotic. The rubomycin resistance was stable and preserved for a long period of time when the line was repeatedly cultivated in mice not exposed to the antibiotic. The tumor cells resistant to rubomycin acquired resistance to olivomycin. DNA histograms of the tumor cells obtained by means of impulse cytophotometry provided determination of the tumor sensitivity and resistance to antitumor agents. It is recommended that impulse cytophotometry be used for the screening of antitumor drugs and development of their administration regimen.

A total of 52-fold passages of leukemia L-1210 were carried out for a year on mice treated intraperitoneally with olivomycin. Prolonged exposure to olivomycin resulted in decreased transplantability of the tumor cells. The tumor cells obtained under the effect of olivomycin were more sensitive (collateral sensitivity) to methotrexate as compared to the cells of the initial strain L-1210. An intramuscular route for transplantation of the tumor cells of leukemia L-1210 is recommended. The dosage intramuscular transplantation of the tumor cells provided simultaneously data on transplantability, tumor size and lifer-time of mice.