New research from the Johns Hopkins Kimmel Cancer Center suggests that a common oral bacterium, Fusobacterium nucleatum, may play a direct role in the initiation and aggressive spread of breast cancer.
While previously linked to colorectal cancer, this study—published in Cell Communication and Signaling—reveals that the microbe can travel through the bloodstream, take up residence in breast tissue, and trigger cellular changes that pave the way for malignancy.
Key Findings of the Study
Led by Dr. Dipali Sharma, a professor of oncology, the team discovered that F. nucleatum does more than just occupy space; it actively alters the biological environment of the breast.
DNA Damage & Mutation: Exposure to the bacterium was found to injure DNA. In response, cells used a "quick-fix" repair mechanism called nonhomologous end joining, which is notorious for introducing genetic errors that can lead to cancer.Accelerated Metastasis: In animal models, the presence of this microbe significantly increased the speed of tumor growth and made it easier for cancer cells to migrate from the breast to the lungs.
Creation of "Pre-Cancer" Conditions: Even before a tumor forms, the bacterium can cause metaplastic and hyperplastic lesions (abnormal tissue growth) and chronic inflammation in breast ducts.
Chemotherapy Resistance: Brief exposure to the pathogen boosted a protein called PKcs, which is associated with "stem-like" behavior in cells, making them more invasive and harder to kill with standard chemotherapy.
The Genetic Connection: BRCA1 Vulnerability
The study highlighted a particularly concerning risk for individuals with BRCA1 mutations. Researchers found that:
- BRCA1-mutant cells possess higher levels of a specific sugar (Gal-GalNAc) on their surface, which acts as a "key" allowing the bacteria to bind and enter the cell more easily.
- These genetically susceptible cells retained the bacteria for longer periods, passing the infection—and the resulting DNA damage—down through multiple generations of cells.
"Nothing happens in a vacuum," Dr. Sharma says. "This bacterium serves as an environmental trigger that can partner with a patient’s DNA to accelerate breast cancer growth."
Why It Matters
This research bridges the gap between large-scale population studies—which have long linked periodontal (gum) disease to breast cancer—and the underlying molecular biology.
While further clinical studies are required, the findings suggest that oral health may need to be evaluated as a significant environmental risk factor in breast cancer prevention, especially for those with a family history of the disease.
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