Drug-mediated antigenic changes in murine leukemia cells: antagonistic effects of quinacrine, an antimutagenic compound.

Because the antigenic changes occurring after in vivo treatment of murine lymphoma cells with 5-(3,3-dimethyl-1-triazenyl)-1H-imidazole-4-carboxamide (DTIC) were suggested to result from DTIC-induced somatic mutation(s), quinacrine dihydrochloride, an antimutagenic compound, was tested for possible antagonistic activity related to this phenomenon. The increased immunogenicity of L1210Ha leukemia occurring at the first transplant generation of DTIC-treated histocompatible (BALB/cCr x DBA/2Cr)F1 male mice or the appearance of strong lymphoma-associated transplantation antigens at transplant generation 6 was prevented by simultaneous administration of quinacrine. However, the compound did not modify the antitumor or immunodepressive activity of DTIC in the mouse. We concluded that the selective antagonistic effect of quinacrine on DTIC-mediated immunogenic changes (DMIC) supported the hypothesis that the molecular mechanism of DMIC could be related to somatic mutation(s).