Abstract
The microorganisms that live symbiotically in human beings are increasingly recognized as important players in health and disease. The largest collection of these microorganisms is found in the gastrointestinal tract. Microbial composition reflects both genetic and lifestyle variables of the host. This microbiota is in a dynamic balance with the host, exerting local and distant effects. Microbial perturbation (dysbiosis) could contribute to the risk of developing health problems. Various bacterial genes capable of producing estrogen-metabolizing enzymes have been identified. Accordingly, gut microbiota is capable of modulating estrogen serum levels. Conversely, estrogen-like compounds may promote the proliferation of certain species of bacteria. Therefore, a crosstalk between microbiota and both endogenous hormones and estrogen-like compounds might synergize to provide protection from disease but also to increase the risk of developing hormone-related diseases. Recent research suggests that the microbiota of women with breast cancer differs from that of healthy women, indicating that certain bacteria may be associated with cancer development and with different responses to therapy. In this review, we discuss recent knowledge about the microbiome and breast cancer, identifying specific characteristics of the human microbiome that may serve to develop novel approaches for risk assessment, prevention and treatment for this disease.
Highlights
The incidence of breast cancer (BC) worldwide has risen to unprecedented levels in recent decades, making it the major cancer of women in many parts of the world nowadays [1]
The link between intestinal microbiota dysbiosis and breast cancer has been investigated in several case-control studies, and many hypotheses have been suggested, some of which underline the possible decrease in the metabolic ability of the microbiota and a weakness of the immune system [48]
The composition and diversity of the gut microbiota were associated with patterns of estrogen metabolism
Summary
The incidence of breast cancer (BC) worldwide has risen to unprecedented levels in recent decades, making it the major cancer of women in many parts of the world nowadays [1]. There has been a strong interest in fully characterizing the microbiota associated with different parts of the body under different health conditions, due to the fact that different published studies have shown that bacterial communities vary across body habitats, establishing complex interactions between bacteria and the host [14,15] These studies have been possible with the use of deep-sequencing technologies (for example, pyrosequencing technique, which provides a qualitative survey of relative abundances of microbiota, and quantitative polymerase chain reaction (qPCR) which may determine quantitative differences), and due to the findings from the Human Microbiome. This review discusses important questions such as the role of the human microbiota in BC development, its ability to modulate inflammation, immunity and metabolism, and the possibility that both intestinal and local microbes could affect cancer prevention and be a new target for therapeutic approaches, improving the prognosis and quality of life of breast cancer patients
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