Human breast cancer cells with a BRCA1 mutation may be more sensitive to damage, lab experiments suggest
A microbe involved in gum disease could fan the flames of breast cancer.
In mice, oral bacteria can increase the size of existing tumors and even trigger the formation of precancerous tumorsthe researchers report on January 15 in Cellular communication and signaling.
The work suggests that harmful bacteria in the mouth can enter the bloodstream, head straight to breast tissue, then crush healthy cells like a wrecking ball. Previous studies have found correlations between oral diseases and breast cancer, but “now we have a direct link,” says Dipali Sharma, an oncology researcher at Johns Hopkins School of Medicine.
In the mouth, Fusobacteria nucleatum helps build biofilms, slime networks of microbes that slips people’s teeth and tongues. Researchers know that this bacteria plays a role in gum disease and have already linked it to head and neck cancers. among others. But F. nucleatum also appears in breast cancer malignancies, Sharma’s team found after analyzing patient datasets. This got the team thinking about what the bacteria might be doing there. The answer was nothing good.
When the researchers injected F. nucleatum In the breast tissue of healthy mice, the animals developed inflamed lesions — not cancer, but a step toward it, Sharma says. Next, the researchers injected the bacteria into the blood of mice already suffering from small breast tumors. Within six weeks, the tumors grew to about three times the size of tumors in mice without bacteria. Additionally, in every mouse with F. nucleatumthe cancer has also spread to the lungs.
Researchers haven’t completely unpacked F. nucleatum a bunch of cancer-promoting tricks, but it appears to involve increased DNA damage, laboratory tests on human cells have revealed. Some cells may also be more prone to damage than others. The bacteria was particularly effective at colonizing human cells with a BRCA1 mutation, a genetic change that increases the risk of breast cancer. This could mean that people with the mutation are more susceptible to cellular attacks caused by F. nucleatum, Sharma said. It’s too early to say for sure.
It is also too early to say whether F. nucleatum can cause breast cancer on its own, or if the results hold up in humans, Sharma says. Firoozeh Samim, specialist in oral medicine, agrees. It is possible that the bacteria is a risk factor that combines with others, like a person’s environmenthealth and genetics, to trigger disease. “Cancer is multifactorial,” explains Samim, of McGill University in Montreal.
Samim was not involved in the new research, but says it goes beyond previous efforts linking the bacteria to the disease. Continued work in this area is important, she says, because it could provide the rationale for integrating oral health care into current cancer prevention efforts.