Studies on mechanisms and blockade of carcinogenic action of female sex hormones.
Tumours of mice are induced by administration of Inj. Hydroxyprogesteroni Caproatis Co. (EP) in a practical subthreshold dose of carcinogenesis or 2.5-5 times the human contraceptive dose (simply referred to as 2.5- to 5-fold dose) combined with whole-body 0.5 Gy gamma-ray irradiation. Malignant transformation of Syrian golden hamster embryo (SHE) cells is also induced by 5-fold dose of EP combined with 0.3 Gy gamma-ray irradiation in vitro, thereby indicating that synergistic carcinogenesis can be obtained by combined use of physical and chemical carcinogens. The mechanisms of synergistic carcinogenesis have been further explained by cytogenetics, damage extent of the target cell DNA and production of free radicals. The Chinese traditional medicine with antioxidating effect (Sulekang Capsule, SC), food additive--butylated hydroxyanisole (BHA) and green tea can effectively inhibit the carcinogenic effect of EP or EP combined with gamma rays in mice. They all have marked ability to scavenge or remove the free radicals and thereby reduce the DNA damage.