[Analysis of uterine sarcoma induced in mice in terms of the two-staged development of tumors].

The results of combined treatment of CBA female mice with 1,2-dimethylhydrazine (DMH) and estradiol dipropionate (EP) are discussed in terms of a two-stage carcinogenesis hypothesis. 20% of mice treated with DMH alone developed uterine sarcomas. EP given after the cessation of DMH-treatment increased sarcoma incidence as high as 60.6% (5 micrograms EP) or 66.7% (10 micrograms EP) and significantly decreased the time of the first tumour appearance. From the standpoint of the two-stage carcinogenesis it is considered possible for EP to influence the tumour-initiating stage.