Cell kinetics and immunogenicity of lymphoma cells treated with 5-(3,3-dimethyl-1-triazeno) imidazole-4-carboxamide (DIC) in vivo

A cycle of treatment with antineoplastic compounds may alter the immunologic properties of experimental tumors leading to an increased survival of syngeneic hosts as compared to that observed with the original parental tumors. However, a loss of growth potential in drug-treated tumors might account for this preferential rejection by syngeneic or by allogeneic animals. In the present study the cell cycle kinetics of parental (L1210 and L5178Y) and DIC-altered leukemic cells (L1210/DIC; L5178Y/DIC) has been evaluated by the establishment of labelled mitosis curves. The in vitro DNA synthesis and cell loss were also investigated. The experimental results indicate that no significant differences in the above properties were present for parental and corresponding drug-treated leukemic sublines. Immunodepressed allogeneic mice were more resistant to lymphoma challenge when inoculated with the DIC-sublines than with the parental lines. On adoptive transfer of immune lymphocytes there was increased survival of allogeneic animals challenged with DIC cells, attributable to an additional immune response to DIC-induced antigens. Thus, parental or DIC-tumors showed similar tumorigenic characteristics, and the increased allogeneic host survival to DIC-cell challenge may be attributed to an additional immune response of the animal against DIC-induced antigens.     

Effects of 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide and its metabolites on Novikoff hepatoma cells.

Studies were undertaken to determine the effects of 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide (DTIC) and its metabolites on the growth and macromolecular synthesis of Novikoff hepatoma cells in culture. DTIC (3.0 mM) in light decreased the viable cell count by 90% within 96 hr. DTIC protected from light, 2-azahypoxanthine, dimethylamine, and 5-aminoimidazole-4-carboxamide, all at 3.0 mM, reduced the rate of cellular proliferation. 5-Diazoimidazole-4-carboxamide (1.0 mM) and 5-(3-methyl-1-triazeno)imidazole-4-carboxamide (3.0 mM) decreased the viable cell count by 99%. Effects on macromolecular synthesis were determined by the rate of incorporation of the appropriate 3H-labeled precursor. Results after 6 hr are given as percentage of controls. DTIC (1.0 mM) in light inhibited DNA (8%), RNA (41%), and protein (63%) synthesis. DTIC (1.0 mM) protected from light inhibited DNA (12%) and RNA (57%) synthesis. 5-Diazoimidazole-4-carboxamide (0.1 mM) inhibited DNA (1%), RNA (9%), and protein (1%) synthesis. 5-(3-Methyl-1-triazeno)imidazole-4-carboxamide (1.0 mM) inhibited DNA (72%) and protein (65%) synthesis but stimulated RNA (127%) synthesis. 2-Azahypoxanthine (1.0 mM) inhibited DNA (43%), RNA 82%) and protein (28%) synthesis. 5-Aminoimidazole-4-carboxamide (3.0 mM) stimulated DNA (354%) and RNA (266%) synthesis. These data show that DTIC is able to generate several toxic metabolites that may be responsible for its biological effects.