An oral bacterium associated with gum disease may be found in breast cancer tissue, where it spreads through the mammary ducts or the blood and can accelerate tumor growth. This study was recently published in Cell Communication and Signaling.
Furthermore, breast cancer cells with certain genetic mutations, such as BRCA1, may be susceptible to the bacteria Fusobacterium nucleatum (F. nucleatum), pointing to a potential link between periodontal disease and breast cancer development, the authors wrote.
“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,” wrote the authors, led by Sheetal Parida of the Johns Hopkins University School of Medicine in Baltimore (Cell Commun Signal, January 15, 2026).
For this study, researchers used several breast cancer cell lines with a normal breast epithelial cell line. To assess how F. nucleatum affects healthy breast tissue, they introduced two strains of the bacterium directly into the mammary ducts of healthy and immunodeficient mice, they wrote.
Colonization with either strain led to abnormal tissue changes, inflammation, DNA damage, and increased cell proliferation in the mammary glands. More severe lesions were observed in mice exposed to F. nucleatum compared with sham-control mice, which showed only mild, age-related tissue changes. Additionally, the number and size of lesions were greater in mice harboring the bacterium.
In human breast tissue samples, higher levels of F. nucleatum and other oral bacteria were found in both benign and malignant disease, and these levels closely matched bacterial abundance in the oral cavity. Gene expression analysis revealed that tumors exposed to F. nucleatum showed increased activity of metastasis-related genes, suggesting the bacterium can accelerate tumor growth and spread, particularly to the lungs, they wrote.
The study did not list any limitations. However, further research is needed to better define how periodontal disease and higher levels of F. nucleatum in the mouth and breast tissue may be linked to breast cancer development, the authors added.
“These results present new insight into the relationship between an oral pathogenic microbe F. nucleatum, breast carcinogenesis, and DNA damage and repair pathway,” Parida and colleagues wrote.
