Effect of genistein supplementation on microenvironment regulation of breast tumors in obese mice

Obesity is an important risk factor for breast cancer in women before and after menopause. Adipocytes, key mediators in the tumor microenvironment, play a pivotal role in the relationship between obesity with cancer. However, the potential of dietary components in modulating this relationship remains underexplored. Genistein, a soy-derived isoflavone, has shown promise in reducing breast cancer risk, attenuating obesity-associated inflammation, and improving insulin resistance. However, there are no reports examining whether genistein has the ability to reduce the effects of obesity on breast tumor development. In this study, we constructed a mammary tumor model in ovariectomized obese mice and examined the effects of genistein on body condition and tumor growth. Moreover, the effects of genistein on the tumor microenvironment were examined via experimental observation of peritumoral adipocytes and macrophages. In addition, we further investigated the effect of genistein on adipocyte and breast cancer cell crosstalk via coculture experiments. Our findings indicate that dietary genistein significantly alleviates obesity, systemic inflammation, and metabolic disorders induced by a high-fat diet in ovariectomized mice. Notably, it also inhibits tumor growth in vivo. The impact of genistein extends to the tumor microenvironment, where it reduces the production of cancer-associated adipocytes (CAAs) and the recruitment of M2d-subtype macrophages. In vitro, genistein mitigates the transition of adipocytes into CAAs and inhibits the expression of inflammatory factors by activating PPAR-γ pathway and degrading nuclear NF-κB. Furthermore, it impedes the acquisition of invasive properties and epithelial‒mesenchymal transition in breast cancer cells under CAA-induced inflammation, disrupting the Wnt3a/β-catenin pathway. Intriguingly, the PPAR-γ inhibitor T0070907 counteracted the effects of genistein in the coculture system, underscoring the specificity of its action. Our study revealed that genistein can mitigate the adverse effects of obesity on breast cancer by modulating the tumor microenvironment. These findings provide new insights into how genistein intake and a soy-based diet can reduce breast cancer risk.