Klenov O. Tumor growth in laboratory animals under soybean products included to the animals' diet

Thesis are devoted to the study of the impact of the soybean products on experimental tumor growth and possible mechanisms of their antitumor effect. Curd-like soybean product with heat-inactivated tripsin inhibitor, included into the animals' diet, significantly (p<0,05) reduced growth rate of carcinosarcoma Walker 256 (by 46%) and Guerin carcinoma (by 21%) in rats and also enhanced lifetime of tumor-bearing animals. Administration of analogous non heat-treated product did not affect tumor growth or accelerated its. "Danprotex B-50" soybean protein concentrate, included into the diet of hybride BDF1 mice with Са755 mammary carcinoma and C3H/Sn mice with RE+ mammary tumors, retarded tumor growth by 60-66% (р<0,05) and enhanced animals' lifetime by 18,3-80% (р<0,05). Phyto-estrogens, isolated from the soybean protein concentrates, were found to be able to compete with estradiol for standard lyophylized estrogen receptors (RE) and for cytoplasmic RE isolated from mouse uterus. Thus, block of the natural estrogen signaling may be one of the mechanisms of cancer-preventive and antitumor effects of soy. At the same time, isoflavon-free soybean protein isolate also inhibited tumor growth, and so phyto-estrogens are not unique agents causing antitumor effect of soy. It was found that antitumor effect of the soybean products has been accomplished with diminished levels of polyamine synthesis, activation of NF-кB transcription factor and expression of ODC, c-Myc and Bcl-xl proteins, involved in tumor growth and proliferation. It was found that soybean products have antioxidant activity.