Inhibition of the growth of sarcoma 180 ascites cells by combinations of inhibitors of nucleic acid biosynthesis and the cupric chelate of kethoxal bis-(thiosemicarbazone).

The tumor-inhibitory jxitency of combinations of the cupric chelate of kethoxal bis(thiosemicarbazone) [Cu(II)KTS] with several compounds that cause inhibition of the synthesis of DNA by different biochemical mechanisms was assessed in Sarcoma 180 ascites cells. Cu(II)KTS prolonged the survival time of tumor-bearing mice, whereas neither cupric chloride, copper stéarate,nor kethoxal bis(thiosemicarbazone) caused a significant lengthening of the life-span of similar animals. Synergistic inhibition of tumor growth was achieved by combinations of either 6-thioguanine or Ar-isopropyl-a-(2-methylhydrazino)-ptoluamide with Cu(II)KTS. The more potent of these drug combinations was the mixture of 6-thioguanine and Cu(II)KTS. In contrast, combinations of cupric chloride or kethoxal bis(thiosemicarbazone) with either 6-thioguanine or A'-isopropyl-