Antigenic changes of L1210 leukemia in mice treated with 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide.

Abstract

Strong antigenic changes were induced in two L1210 leukemia lines (L1210 Cr and L1210 Ha) after several passages in CDF1 and BDF1 mice treated with 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide (DIC). The leukemic cells of both lines originally compatible with DBA/2 and related hybrid hosts elicited a pronounced allograft reaction in the same animals. The L1210 Cr line was sensitive to the antitumor activity of DIC while L1210 Ha was not. Since no specific relationship could be found between the origin of drug resistance and the appearance of antigenic changes, any hypothesis based on selection of spontaneous mutants by DIC would appear to be excluded. In addition the possibility that DIC might play a direct role as a hapten on tumor cells was ruled out. DIC was found to exert a strong inhibition of the allograft reaction. However, the origin of antigenic lines could not be attributed to the immunosuppressive activity of DIC. It would appear that DIC acts in some way on tumor cells, changing their antigenic properties and preventing the immunoselection of the transformed cells by the host. It was suggested that DIC could activate a latent virus of L1210 leukemic cells or induce somatic mutation at the level of histocompatibility antigens.