New Insights into Gut Health and Breast Cancer Metastasis

A study suggests that gut health may influence the spread of breast cancer to other parts of the body. Researchers found that an unhealthy gut leads to a buildup of bile acids, which might drive breast cancer metastasis. This discovery may offer new ways to prevent the spread of breast cancer and potentially save lives.

Research at the University of Virginia Comprehensive Cancer Center, under the guidance of Melanie Rutkowski, Ph.D., focused on the impact of gut microorganisms on the spread of hormone receptor-positive breast cancer. Rutkowski explained, “We found that when the gut microbiome is unbalanced and unhealthy, the control of bile acid levels is lost. These are potent signaling molecules that, when not properly regulated, disrupt metabolism and immune function. This disruption creates conditions throughout the body that make it easier for breast tumors to spread.”

Hormone receptor-positive (HR+) breast cancer is the most frequent type of metastatic breast cancer. Hormone receptors are cell proteins activated when hormones bind to them, which can promote cancer growth. According to the Breast Cancer Research Foundation, four out of five breast cancers are hormone receptor-positive. Around 225,000 cases of HR+ breast cancer occur annually among American women, and metastatic spread makes treatment challenging and increases mortality risk.

Rutkowski stated that an unhealthy microbiome cannot properly regulate bile acids. This dysregulation can harm health, metabolism, and the immune system, thus encouraging metastasis. She proposed that reducing breast cancer spread might be possible by altering bile acid composition or using bile acid sequestrants, which are FDA-approved for metabolic diseases.

Previous studies have linked gut imbalance with poor outcomes, but Rutkowski’s work identified bile acid buildup as a trigger for inflammation that promotes the spread of cancer cells.

Study co-author Audrey Putelo, Ph.D., noted that the measurability and modifiability of bile acids could lead to new approaches for identifying high-risk patients and reducing metastasis risks. The researchers found connections between elevated bile acids, insulin resistance, and reduced survival in HR+ breast cancer patients, while those receiving bile acid-suppressing drugs often lived longer. More research is required to see if these drugs directly contribute to survival benefits.

Rutkowski described the results as “extremely encouraging,” and they aim to discover whether existing FDA-approved drugs can prevent cancer spread. If validated, this could support the use of well-tolerated drugs for preventing metastatic breast cancer. She explained ongoing analysis of patient data and efforts to understand immune consequences of bile acid signaling in tissues potentially affected by metastasis, with hopes of identifying additional targets to reduce breast tumor spread.