By Eliza Dysart
Post-menopausal women with breast cancer have different gut bacteria than healthy women, adding to growing evidence that the microbiota plays an important role in cancer development and overall health, UF Health Cancer Institute researchers found.
“The main finding is that there are significant differences in gut microbiota diversity between post-menopausal breast cancer patients and healthy controls, with reduced diversity in patients with cancer,” said Coy Heldermon, M.D., Ph.D., a professor in the UF Division of Hematology & Oncology and senior author of the study.
The study, published recently in the journal Scientific Reports, analyzed stool samples from 27 post-menopausal breast cancer patients who had not received treatment and 25 post-menopausal women without cancer to compare differences in gut bacterial composition.
Women with breast cancer had less diverse gut microbiomes, meaning their intestines contained a smaller variety of bacterial species than those of healthy women. This does not necessarily mean they had fewer bacteria overall; rather, their gut bacterial communities were less varied and often dominated by a smaller number of bacterial types.
The difference was even stronger in patients with ER+HER2- breast cancer, a type influenced by estrogen. Researchers also found lower levels of a helpful type of bacteria called Akkermansia, which supports gut health and the immune system.
“Akkermansia has been linked to gut barrier function and metabolic and immune health,” said Heldermon, a member of the UF Health Cancer Institute’s Cancer Targeting and Therapeutics research program.
The project developed over several years through a mentorship model. Students contributed at multiple stages of the research process, from patient recruitment to data analysis and manuscript preparation.
“We had multiple mentees involved over the years, many of whom started as undergraduates and continued into medical school,” he said. “They were essential in processing and analyzing the samples.”
Nadia Kabbej, M.D., the study’s first author who graduated from the UF College of Medicine this spring, got involved as an undergraduate working in Heldermon’s lab. She is now doing a internal medicine residency at Beth Israel Deaconess Medical Center in Boston, Massachusetts.
She recruited patients in clinic, determined their eligibility, obtained consent and helped with stool sample collection. Her role expanded significantly as the project progressed, eventually leading the data analysis and manuscript writing as a medical student.
“As first author, I interpreted the results of the data analysis, performed the literature review, wrote the manuscript and addressed reviewer comments during revisions,” Kabbej said.
Heldermon said Kabbej’s work reflects the lab’s broader focus on mentorship and training future physician-scientists.
“The goal is to expose trainees early to research so they can develop the skills to continue this work in their careers,” Heldermon said.
Researchers emphasized that the findings do not show that gut bacteria cause breast cancer.
“At this point, all we can say is association,” Heldermon said. “We cannot conclude causation, and it could be that disease itself alters the microbiome.”
Kabbej said the findings provide a foundation for future research exploring whether microbiome patterns could guide diagnosis or treatment strategies.
Future studies may examine whether modifying the microbiome can influence tumor growth in experimental models.
“We are still at the beginning of understanding this relationship,” Heldermon said. “But this gives us a foundation for future work.”
UF Health Cancer Institute members Christian Jobin, Ph.D., and Raad Gharaibeh, Ph.D., are co-authors on the study, which received funding through a UF Health Cancer Institute pilot grant, a UF Interdisciplinary Center for Biotechnology Research pilot grant and the Bristol Myers Squibb Foundation.
