There are trillions of different types of bacteria found in our gut, most of which help to maintain our immune systems and aid with digestion.  However, an imbalance of the “good” and “bad” bacteria in the gut could trigger disease or increase the risk of colon cancer.  According to two new studies, a type of bacteria found in the mouth may affect immune response when it reaches the gut to trigger colorectal cancer.  The studies are published in the August 14th online issue of the Cell Host & Microbe journal and they focus on the effects of Fusobacteria.  The researchers hope that their findings will improve the prevention and treatment methods of colorectal cancer.

Fusobacteria and Colon Cancer

Colorectal cancer is the second most fatal type of cancer in the United States and it has been discovered that Fusobacteria from the mouth are present in the tissues of patients with colorectal cancer.  What has never been clear until the publication of these recent studies is if these gut microbes can trigger cancer tumors.  The researchers in the first study found Fusobacteria in benign tumors that became cancerous, suggesting that they may have a role in the formation of a tumor.  This hypothesis was strengthened by the team’s discovery of the bacteria in mice bred to have a form of colorectal cancer.  The Fusobacteria in the mice summoned myeloid cells which are known to trigger cancer by penetrating tumors and causing inflammations.

According to senior author Wendy Garrett of the Harvard School of Public Health and the Dana-Farber Cancer Institute, “Fusobacteria may provide not only a new way to group or describe colon cancers but also, more importantly, a new perspective on how to target pathways to halt tumor growth and spread.”

FadA Molecule and Colon Cancer

The second study which was performed by a different research team, led to the discovery of a molecule on the surface of a Fusobacterial cell that attaches to and invades human colorectal cancer cells.  This molecule is called Fusobacterium adhesion A or FadA and it initiates cancer growth by switching on certain genes and causing inflammation in tumors.  The researchers tested tissue from healthy individuals as well and found that these tissues had much lower levels of FadA than those from individuals with colorectal tumors.  In addition to discovering the FadA molecule, the researchers also found a compound that can stop FadA from affecting cancer cells.  A study published earlier this year identified a group of innate lymphoid cells in mice that ignore “good” gut bacteria to maintain a favorable balance of “good” and “bad” bacteria.

Senior author Yiping Han of Case Western Reserve University School of Dental Medicine claims, “We showed that FadA is a marker that can be used for the early diagnosis of colorectal cancer and identified potential therapeutic targets to treat or prevent this common and debilitating disease.”