Potentiation of antitumor drug action by centrophenoxine: specificity.

The cytotoxic action of certain antitumor agents is potentiated by centrophenoxine although centrophenoxine itself is not an antitumor agent. Previous investigations have suggested that centrophenoxine might potentiate the cytotoxicity produced by antitumor drugs that alkylate, and other modalities that damage, DNA, but that it would not potentiate the cytotoxicity produced by antitumor drugs that inflict cellular damage in other ways. To test this hypothesis, the antitumor effects of X-irradiation UV-irradiation, alkylating agents and antitumor drugs that are not ordinarily considered to be alkylating agents were determined in the presence and absence of centrophenoxine. Mouse P388 lymphoma cells growing in static suspension culture were used as the experimental tumor. The cytotoxic action of most alkylating agents was found to be potentiated by centrophenoxine; Included in this group were several difunctional nitrogen mustards, two ethylenimines, a nitrosourea and mitomycin C. Greatest enhancement, 7-fold, was of chlorambucil antitumor activity. Centrophenoxine did not potentiate the lethality of X- or UV-irradiation or the cytotoxicity of several antineoplastic drugs that are not alkylating agents.