Gum Disease Bacterium Linked to Breast Cancer Growth and Spread
A common oral bacterium associated with gum disease may play a role in initiating breast cancer, accelerating tumor growth, and promoting its spread, according to new research from the Johns Hopkins Kimmel Cancer Center and the Bloomberg~Kimmel Institute for Cancer Immunotherapy 1. The study, published in Cell Communication and Signaling, focuses on Fusobacterium nucleatum, a microbe previously linked to colorectal and other cancers.
How the Bacterium Impacts Breast Cancer
Researchers discovered that F. Nucleatum can travel through the bloodstream and colonize in breast tissue, where it causes inflammation and early cellular changes linked to cancer 4. In animal models of human breast cancer, the presence of this bacterium sped up tumor growth and increased the spread of cancer cells to the lungs 2.
“The key takeaway is that this oral microbe can reside in breast tissue and that there is a connection between this pathogen and breast cancer,” explained Dipali Sharma, professor of oncology and a John Fetting Fund for Breast Cancer Prevention investigator 1.
DNA Damage and Cellular Changes
Experiments revealed that exposure to F. Nucleatum leads to the formation of metaplastic and hyperplastic lesions – noncancerous changes where cells either multiply excessively or transform into a different type – in breast tissue, accompanied by inflammation, DNA damage, and increased cell growth 3. The bacterium damages cellular DNA and activates repair systems prone to errors, specifically nonhomologous end joining, which can introduce mutations.
Exposure to F. Nucleatum also increased levels of a protein called PKcs, linked to greater cancer cell movement, invasion, stem-like traits, and resistance to chemotherapy 4.
Increased Risk in BRCA1-Mutant Cells
Epithelial cells lining the breast ducts and breast cancer cells carrying BRCA1 mutations appear particularly susceptible to the effects of F. Nucleatum 1. These BRCA1-mutant cells have elevated levels of a surface sugar (Gal-GalNAc), which helps the bacteria attach and enter cells. These cells absorb more F. Nucleatum and retain it over time, intensifying DNA damage and cancer-promoting effects.
“Our findings reveal a link between oral microbes and breast cancer risk and progression, particularly in genetically susceptible individuals,” says Sharma 4. “Nothing happens in isolation. The results suggest that multiple risk factors come together with F. Nucleatum acting as an environmental factor that may cooperate with inherited BRCA1 mutations to promote breast cancer and tumor aggressiveness.”
Future Research and Oral Health Implications
Researchers emphasize the need for further investigation to determine how these findings translate to patient care. Future studies will explore whether maintaining good oral health could play a role in reducing breast cancer risk 1.
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