Inhibitory effect of synthetic interferon inductor Cycloferone on 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

The effect of a synthetic interferon inductor Cycloferone on colon carcinogenesis was firstly studied in rats. Seventy-five 2-month-old outbred female LIO rats were subdivided into three groups and were weekly exposed to 15 s.c. injections of 1,2-dimethylhydrazine (DMH) at a single dose of 7 mg/kg body wt. From the day of the fist injection of DMH rats from group 2 were given weekly i.p. injections of Cycloferone (62.5 mg/kg) until the end of the experiment. DMH-treated rats (group 3) were exposed to weekly i.p. injections of Cycloferone (62.5 mg/kg) starting in the week after the last injection of the carcinogen. Rats from group 1 were exposed to DMH and treated weekly with 0.2 ml i.p. of normal saline. Additional groups of rats were treated weekly with Cycloferone (62.5 mg/kg) or with 0.2 ml of saline. The experiment was ended 6 months after the first injection of DMH. In DMH-treated rats (groups 1, 2 and 3) colon adenocarcinomas developed in 87, 61 and 59%, respectively. The number of colon tumors per tumor-bearing rat was 2.5, 1.9 and 1.3 in groups 1, 2 and 3, respectively. Treatment with Cycloferone significantly inhibits carcinogenesis in ascending and descending colon. The incidence of tumors of the rectum was decreased in the group 2 as compared with the group 1. There were no cases of tumors of rectum in rats from group 3. The treatment with Cycloferone alone as well as with normal saline failed to induce any tumors in rats. Thus, our results demonstrated inhibitory effect of Cycloferone on colon carcinogenesis induced by DMH in rats.