Promoting and synergistic effects of chrysazin on 1,2-dimethylhydrazine-induced carcinogenesis in male ICR/CD-1 mice

The modifying effects of chrysazin on 1,2-dimethylhydrazine(DMH)-indueed colon and liver carcinogenesis were examined inmate ICR/CD-1 mice. Starting at 6 weeks of age, mice were dividedinto four groups, two of which were treated with s.c. injectionsof DMH (20 mg/kg body wt) once a week for 12 weeks. A week afterthe final injection of DMH, one group was kept on the basaldiet throughout the study (group I), and the other group wasfed the diet containing chrysazin (mixed in basal diet at 0.2%concentration) alone for 42 weeks (group II). The other twogroups were injected with normal saline and given the diet containing0.2% chrysazin for 42 weeks (group III), or the basal diet duringthe experiment (group TV). The incidence and multiplicity ofcolon tumors of group II were significantly greater than thoseof group I (P<0.05, P<0.01). The incidence and multiplicityof the hepatocellular neoplasms of group II were larger thanthose of group I (P< 0.002, P< 0.02 respectively). Ingroup III, colon tumors were not found, though a few liver neoplasmsand severe inflammatory lesions of the colon were observed.The activity of ornithine decarboxylase of the colonk mucosain mice exposed to chrysazin was stronger than that of animalswithout chrysazin. The results suggest that the promoting effectof chrysazin is probably related to an increase of cell proliferationin the target organ. A synergistic effect of DMH with chrysazinwas also observed in liver tumorigenesis.