Inhibitory Mechanisms of Soybean Extract on the Development of Breast Cancer Through Modulation of Cellular Immune Response

Background: Breast cancer is the most frequently diagnosed cancer in women worldwide. Consumption of soy products has been reported to reduce the incidence of and mortality rate for some cancers, including breast cancer. However, there are limited in vivo studies on the inhibitory effect of soybean extracts on breast cancer. Objectives: To examine the effect of soybean extracts on breast cancer cellular immunity and to determine the role of CD4⁺ and CD8⁺ T cells in the development and outcome of breast cancer. Material and Methods: Rat were induced with DMBA 11 times to get a breast cancer model. A soybean extract was given at different doses starting one week before DMBA induction and continued until the end of the study. At the end of the study, peripheral blood was collected, and the lymphocytes were examined using flow cytometry. Results: The phytochemical screening of soybean extract, using the Q-TOF LC/MS method, detected four bioactive components from the isoflavone and saponin groups. The incidence of tumor formation in the NeC, SE-D250, SE-D500, and SE-D1000 groups was 100%, 83%, 33%, and 33%, respectively. The highest proportion of CD4+ T cells was found in the NeC (69.35%), while the lowest was in the SE-D1000 (63.75%). The highest and lowest proportions of CD8+ T cells were found in the SE-D1000 and NeC groups, at 35.95% and 31.15%, respectively. Conclusions: The soybean extract was able to reduce the incidence of breast tumor formation in DMBA-induced rat in a dose-dependent manner. The soy extract group's CD4+/CD8+ ratio was close to that of healthy rats compared to the DMBA-induced group without soy extract. A lowered CD4+/CD8+ ratio is followed by a lower risk of tumor formation.