thymic-factor--circulating and 1-4-benzoquinone-guanylhydrazone-thiosemicarbazone

The antineoplastic activity of 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone (ambazone) against murine leukemia P388 was found to be markedly reduced in 12- and 18-month-old mice as compared to young animals. The immune response against sheep red blood cells (SRBC), a T cell-dependent antigen, was also strongly diminished in tumor-free old mice and was further suppressed after ambazone treatment. Since the antileukemic effect of ambazone disappeared more or less in congenitally athymic nude mice, in neonatally thymectomized or silica-pretreated animals, it has been concluded that the action of the compound seems to be limited to young adult immunocompetent tumor-bearing hosts. Therefore immunosenescence, primarily of T cell functions of old tumor-bearers, may represent a decisive factor influencing the antileukemic, especially curative effect of ambazone in aged animals. A combined treatment with ambazone and immunomodulators (thymalin or a splenopentin derivative) failed to improve the antileukemic effect in young and old leukemia P388-bearing mice.

Topics: Adjuvants, Immunologic; Aging; Animals; Antineoplastic Agents; Female; Immune System; Immunosuppression Therapy; Leukemia P388; Leukemia, Experimental; Mice; Mice, Inbred DBA; Mice, Inbred Strains; Mitoguazone; Peptide Fragments; Thymopoietins; Thymus Hormones; Tissue Extracts