An oral bacterium commonly associated with gum disease has been detected in breast cancer tissue, where it may spread through mammary ducts or the bloodstream and accelerate tumor growth, according to a new study published in Cell Communication and Signaling.
Researchers found that Fusobacterium nucleatum—a pathogenic microbe linked to periodontal disease—can colonize breast tissue and promote cancer development and metastasis. The findings suggest a potential biological link between oral health and breast cancer, particularly in patients with specific genetic vulnerabilities.
The study, led by Sheetal Parida of the Johns Hopkins University School of Medicine, reports that breast cancer cells carrying mutations such as BRCA1 may be especially susceptible to F. nucleatum infection. The authors note that this susceptibility could help explain how periodontal disease may contribute to breast cancer initiation or progression.
“Oral microbe F. nucleatum also inhabits breast cancer tissue, and mammary duct colonization or hematogenous administration with pathogenic F. nucleatum triggers metaplastic lesions and augments breast cancer growth and metastasis,” the researchers wrote.
To investigate the bacterium’s effects, the team conducted experiments using multiple breast cancer cell lines alongside a normal breast epithelial cell line. They also introduced two strains of F. nucleatum directly into the mammary ducts of both healthy and immunodeficient mice.
Mice exposed to the bacterium developed abnormal tissue changes, including inflammation, DNA damage, and increased cellular proliferation in the mammary glands. These changes were significantly more pronounced than those seen in control mice, which exhibited only mild, age-related tissue alterations. Researchers also observed a higher number and larger size of lesions in mice colonized by F. nucleatum.
Analysis of human breast tissue samples revealed elevated levels of F. nucleatum and other oral bacteria in both benign and malignant breast disease. Notably, bacterial levels in breast tissue closely mirrored bacterial abundance in the oral cavity, reinforcing the potential oral–breast microbial connection.
Further gene expression analysis showed that tumors exposed to F. nucleatum exhibited increased activation of genes associated with metastasis. This heightened activity was linked to accelerated tumor growth and spread, particularly to the lungs, the authors reported.
While the study did not specify formal limitations, the researchers emphasized that additional investigation is needed to clarify how periodontal disease and elevated oral bacterial levels may influence breast cancer development.
“These results present new insight into the relationship between an oral pathogenic microbe F. nucleatum, breast carcinogenesis, and DNA damage and repair pathways,” Parida and colleagues concluded.
