A recent discovery establishes a link between an oral bacterium and the development of breast tumors. Work indicates that a microbe is capable of migrating to breast tissue, where it activates processes promoting tumor growth.
Published in
Cell Communication and Signaling, this research focuses on *Fusobacterium nucleatum*. Already implicated in other cancers, this bacterium can travel from the mouth via the bloodstream to implant itself in the breast. The team from Johns Hopkins University showed that its presence there causes inflammation as well as early cellular lesions.
Microscopic image showing the bacterium *F. nucleatum* in a breast cell with BRCA1 mutation, illustrating its interaction.
Credit: Drs. Sheetal Parida and Dipali Sharma
To achieve these results, scientists introduced the bacterium directly into the mammary ducts of mice. They then observed the appearance of non-cancerous lesions, accompanied by inflammation and DNA damage. These alterations create an environment conducive to the emergence of tumors, thus accelerating the progression of the disease.
A precise molecular mechanism has been highlighted. The bacterium damages the DNA of cells and activates repair pathways likely to introduce errors. This phenomenon leads to increased expression of proteins linked to the migration of cancer cells and their resistance to treatments.
Cells with mutations in the BRCA1 gene are particularly sensitive to this bacterium. Their surface indeed facilitates the adhesion and penetration of the microbe, which amplifies the damage and tumor-promoting effects. This increased vulnerability indicates that genetic and environmental factors can combine to raise the risks.
Scientists emphasize the need for additional investigations to determine whether oral health should be integrated among risk factors in breast cancer prevention, particularly for genetically predisposed individuals.
The journey of bacteria in the body
Bacteria present in the mouth can sometimes leave their natural habitat to spread elsewhere in the body. This phenomenon, called bacterial translocation, occurs when microbes cross tissue barriers, such as those of inflamed gums, and enter the bloodstream.
Once in the blood, these bacteria can reach various organs, including distant sites like the breast. The immune system normally tries to eliminate them, but some bacteria manage to avoid these defenses and settle in new tissues.
When they establish themselves, these bacteria can cause local inflammation. This body reaction, although intended to fight the infection, can also damage surrounding cells and disrupt their normal functioning, creating a favorable ground for other health problems.