Does Gut-breast Microbiota Axis Orchestrates Cancer Progression?

Breast cancer, even today, can cause death. Therefore, prevention and early detection are fundamental factors. The mechanisms that favour it are genetic and epigenetic, and seem to play a significant role; also, the microbiota can change estrogen levels and can induce chronic inflammation in the neoplastic site, alternating the balance between proliferation and cell death. Activated steroid hormone receptors induce transcription of genes that encode for proteins involved in cell proliferation and activate another transduction pathway, inducing cell cycle progression and cell migration. These important studies have allowed to develop therapies with selective modulators of estrogen receptors (SERMs), able to block their proliferative and pro-tumorigenic action. Of fundamental importance is also the role played by the microbiota in regulating the metabolism of estrogens and their levels in the blood. There are microbial populations that are able to promote the development of breast cancer, through the production of enzymes responsible for the deconjugation of estrogens, the increase of these in the intestine, subsequent circulation and migration to other locations, such as the udder. Other microbial populations are, instead, able to synthesize estrogen compounds or mimic estrogenic action, and interfere with the metabolism of drugs, affecting the outcome of therapies. The microbial composition of the intestine and hormonal metabolism depend largely on eating habits; the consumption of fats and proteins favours the increase of estrogen in the blood, unlike a diet rich in fiber. Therefore, in-depth knowledge of the microbiota present in the intestine-breast axis could, in the future, encourage the development of new diagnostic and therapeutic approaches to breast cancers.