Antimetastatic action and hematological toxicity of p-(3,3-dimethyl-1-triazeno)benzoic acid potassium salt and 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide used as prophylactic adjuvants to surgical tumor removal in mice bearing B16 melanoma

The treatment of mice bearing i.m. B16 melanoma with equitoxic dosages of the clinically used 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) and of its benzenoid water-soluble analogue p-(3,3-dimethyl-1-triazeno)benzoic acid potassium salt (DM-COOK) prior to surgical tumor removal results in a remarkable proportion of cures, even when the treatment is started on already palpable tumors for which surgery alone is ineffective. The survival time of mice which are not cured is also significantly increased with DM-COOK. At the same time, DM-COOK does not affect artificial metastases or spontaneous metastases in mice undergoing surgery and treated with DM-COOK postoperatively. Inhibition of i.m. tumor growth in surgical experiments, and of s.c. tumors in mice not treated with surgery, is significant, although not as pronounced as is necessary to obtain significant prolongation of the life span of the host; the survival time of mice with s.c. tumors treated with both drugs is indeed not significantly increased. DM-COOK thus appears to exert selective antimetastatic effects, unrelated to cytotoxicity for tumor cells, against B16 melanoma in addition to those reported for Lewis lung carcinoma and M5 ovarian reticular cell sarcoma; its therapeutic usefulness is evidenced in adjuvant surgical experiments. DM-COOK, unlike DTIC, is devoid of hematological toxicity for the host. Since, in leukemic mice, it is at least as active as DTIC in increasing the life span of the treated animals, it appears to be an advantageous substitute for DTIC that could undergo preliminary clinical trial.     

Comparison of the antitumor activity of DTIC and 1-p-(3,3-dimethyl-1-triazeno) benzoic acid potassium salt on murine transplantable tumors and their hematological toxicity

Summary This study describes a comparison of 1-p-(3,3-dimethyl-1-triazeno)benzoic acid potassium salt (DM-COOK) and imidazole-4-carboxamide,5-(3,3-dimethyl-1-triazeno) (DTIC) with reference to antitumor activity on different murine tumors and hematological toxicity. DM-COOK appeared comparably or slightly more effective in L1210, P388, and M5 tumors in the mouse. However, when the treatment of mice bearing M5 with DM-COOK was combined with surgical removal of the primary tumor, the host's life-span was highly significantly prolonged. The two drugs showed similar activity in an M5 variant selected for resistance to cyclophosphamide. In L1210 Ha, a leukemia that is spontaneously resistant to DTIC, DM-COOK was not effective.Both DM-COOK and DTIC caused transient leukopenia with a maximum WBC fall of 57% and 71% compared with control values. DM-COOK's greater chemical stability might be an advantage, as the decomposition of DTIC is thought to lead to products responsible for some toxic effects in humans. Like other phenyldimethyltriazenes DM-COOK, is a good candidate for clinical trials because its water solubility eliminates formulation problems.     

In vitro mutagenic activity of 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) in eukaryotic and prokaryotic cells

The in vitro mutagenic activity of 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide(DTIC), has been studied in bacteria and Chinese hamster cellswith and without metabolic activation by rat liver microsomes.DTIC was found to be highly mutagenic in the two systems. Itis noteworthy that DTIC in the prokaryotic systems did not requiremetabolic activation to be effective. By comparing the mutagenicactivity on bacteria of DTIC and of its monomethyl- and hydroxymethyl-derivatives(MIC and HMIC), it is evident that MIC and HMIC display a patternof mutagenicity different from DTIC. It suggests that neitherMIC nor HMIC are the direct responsible metabolites for themutagenic activity of DTIC in bacteria.     

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.     

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.