Scientists have long known that the trillions of bacteria living inside our intestines influence much more than digestion.
This community of microorganisms, called the gut microbiome, helps regulate the immune system, produces important nutrients, and affects many chemical signals throughout the body. When the balance of these bacteria is disturbed, a condition known as gut dysbiosis develops.
Growing evidence suggests this imbalance may contribute to diseases ranging from diabetes to heart disease and even cancer. Now, researchers at the University of Virginia Comprehensive Cancer Center have discovered another important connection.
Their new study, published in Nature Communications, suggests that an unhealthy gut may encourage one of the most common forms of breast cancer to spread to other parts of the body.
The researchers focused on hormone receptor-positive, or HR-positive, breast cancer. This is the most common type of breast cancer, with roughly 225,000 new cases diagnosed each year among women in the United States.
Although many patients respond well to treatment when the disease is found early, HR-positive breast cancer can spread silently to organs such as the lungs and lymph nodes. Once this happens, treatment becomes much more difficult and survival rates fall significantly.
The UVA team wanted to understand why previous studies had linked poor gut health with worse breast cancer outcomes. They discovered that changes in the gut microbiome disrupted the body’s normal control of bile acids.
These substances are made by the liver to help digest fats, but they also act as powerful chemical messengers that influence metabolism and the immune system.
When healthy gut bacteria are lost, bile acids can build up in abnormal amounts and forms. In laboratory mice, the researchers found that this buildup triggered inflammation in breast tissue, creating conditions that made it easier for cancer cells to escape the original tumor and spread, especially to the lungs.
The findings provide a biological explanation for how gut health may influence cancer progression.
The scientists then examined information from people with HR-positive breast cancer. Patients with higher bile acid levels and insulin resistance generally had poorer survival.
They also observed that patients with metastatic disease who happened to be taking bile acid sequestrants, medicines already approved to treat certain metabolic disorders, appeared to live longer. However, the researchers stress that this observation does not prove the medicines caused the improved survival because the study was not a clinical trial.
Even so, the results are encouraging because bile acid sequestrants are already widely used and generally well tolerated. Researchers believe future clinical trials could test whether these medicines, or treatments that restore healthy gut bacteria, might reduce the risk of breast cancer spreading.
The study has important strengths, including combining laboratory experiments with patient data to strengthen the findings. However, most of the biological work was performed in mice, so further studies in people are still needed.
Overall, this research highlights an exciting new link between the gut microbiome and breast cancer metastasis. If future studies confirm these results, protecting gut health or targeting bile acids could become a completely new strategy to prevent cancer spread and improve survival for thousands of patients.
If you care about breast cancer, please read studies about how eating patterns help ward off breast cancer, and soy and plant compounds may prevent breast cancer recurrence.
For more health information, please see recent studies about how your grocery list can help guard against caner, and a simple way to fight aging and cancer.
Source: University of Virginia.
