Gum disease and colon cancer, a disease that affects one out of 23 adults, are known to be linked. But how the one might be driving the other has not been known—until now. A new study has discovered what it is in our mouths that causes colon cancer to become most deadly…and may lead to better tests and new treatments.

Fusobacterium nucleatum is a common bacterium found in the mouth that plays a role in forming dental plaque, which can lead to tooth decay, gingivitis and periodontitis. The bacterium also has been implicated in diseases outside the mouth, including colorectal cancer, atherosclerosis, rheumatoid arthritis and Alzheimer’s disease. In fact, research has found that about one-third of colorectal cancer patients test positive for F. nucleatum bacteria—and those patients usually have more aggressive tumors.

Researchers at Columbia University College of Dental Medicine had previously discovered that F. nucleatum produces a molecule called FadA adhesin. They also observed that FadA adhesin interacted with cancerous colon cells but not with healthy colon cells. To learn more, the researchers reviewed cellular data from more than 450 patients with colorectal cancer.

Results: The researchers found that FadA adhesin molecules bind to a protein called Annexin A1 that is produced only in the cancerous cells, not in the noncancerous cells. Annexin A1 stimulates cancer growth and leads to a more aggressive and deadly prognosis. In fact, the patients in the study with the highest levels of Annexin A1 in their cancer cells had the fastest-growing cancers.

Vicious cycle: FadA adhesin molecules bind to the Annexin A1 protein, triggering the cells to produce more Annexin A1. This in turn causes more binding and more cancer growth—a sequence called a “positive feedback loop” in scientific terms.

The researchers hope that the results of their study might lead to development of a test for Annexin A1 levels to identify which cancers are more likely to become aggressive, as well as new treatments for colorectal cancer.

While the researchers were able to show in cell cultures and mouse studies that blocking Annexin A1 prevented F. nucleatum from binding to cancer cells, no research has yet shown that reducing oral F. nucleatum will protect people with colorectal cancer from more aggressive disease. However, it is known that F. nucleatum increases with the severity of gum disease and is also higher in smokers. So, if you have been diagnosed with colorectal cancer it makes sense to be especially persistent about maintaining good oral hygiene. And if you smoke, here’s one more good reason to quit.