Recent research indicates that gut health might influence the spread of breast cancer to other areas of the body. An accumulation of bile acids resulting from an unhealthy gut could potentially promote the metastasis of breast cancer, opening avenues for new preventive strategies.
The study, conducted by the University of Virginia Comprehensive Cancer Center under the guidance of Dr. Melanie Rutkowski, explores how intestinal microorganisms contribute to the distribution of hormone receptor-positive breast cancer. Dr. Rutkowski explained to Newsweek that an unbalanced gut microbiome causes a loss of control over bile acid levels. These molecules, when not regulated, disrupt metabolism and immune functions, creating an environment conducive to cancer spread.
Hormone receptor-positive (HR+) breast cancer is a form of metastatic breast cancer. Hormone receptors are proteins that become active when hormones attach to them, potentially leading to cancer growth. Approximately four out of five breast cancer cases are HR+, according to the Breast Cancer Research Foundation. Annually, around 225,000 HR+ breast cancer diagnoses occur in American women. Metastasis significantly complicates treatment and increases mortality risk.
“Our research indicates that an unhealthy gut microbiome impedes the regulation of bile acids, essential signaling molecules. This creates systemic conditions that favor metastasis,” stated Dr. Rutkowski via EurekAlert!.
The study suggests modifying bile acid composition or employing bile acid sequestrants, FDA-approved for metabolic diseases, could reduce breast cancer metastasis. Prior studies linked gut microbiome imbalance to poor patient outcomes. This new research identifies bile acid buildup as a trigger for inflammation, promoting cancer cell spread.
Co-author Dr. Audrey Putelo noted, “Measuring and altering bile acids offers new avenues for identifying high-risk patients and reducing metastatic disease risk.” Elevated bile acids, along with insulin resistance, were associated with decreased survival in HR+ breast cancer patients. Conversely, patients with metastatic disease who received bile acid-suppressing medications often had improved outcomes. Further investigation is required to confirm if these medications directly cause the observed benefits.
Dr. Rutkowski described the findings as “extremely encouraging” and expressed the aim to discover if existing FDA-approved drugs might prevent initial cancer spread. This could justify using well-tolerated drugs for preventing metastatic breast cancer. Ongoing analysis of patient data seeks to determine if long-term drug use can halt tumor spread. Additionally, due to currently undeveloped methods for stably altering the microbiome, understanding bile acid signaling’s immune implications in tissues prone to tumor spread is essential for identifying further intervention targets.
Reference: Putelo, A. M., Bajgai, S., Poblete, M. K., Guido G., Lanfranca, M. P., Rutkowski. M. R.; et al. Commensal Dysbiosis Alters Primary Bile Acid Signaling to Drive Mammary Gland Inflammation and Breast Tumor Dissemination. Cancer Res 2026; https://doi.org/10.1158/0008-5472.CAN-25-4466
Contact Newsweek editors on this story: Kara Dolman and James Debens
Understanding the Cyclospora Outbreak and Its Connection to Sewage Contamination 
New Insights into PMOS and GLP-1 Drugs 
Public Health Challenges with Proposed Vaccination Order 
Understanding Medicare Extra Help and Its Benefits 
Trump’s Remarks on Childhood Vaccines Spark Debate 
CDC Reports Drug-Resistant Fungus Candida Auris Cases Across 27 States