Plaque-causing bacteria may cause colorectal cancer

Fusobacterium nucleatum.
Courtesy of the University of Adelaide

CancerDigest – If you still need a reason to floss, how about this? The bacteria that causes plaque 

has recently been linked to colorectal cancer. 

And now new research shows a possible mechanism for how the microbe changes cells in the intestines to stimulate cancer growth.

The microbe is Fusobacterium nucleatum, which is linked to several diseases of the mouth, head and neck and more recently colorectal cancer. But it was unclear how it might alter the genes in colon cells to cause cancer.

A pair of studies published Aug. 14, 2013 in Cell Host & Microbe, by researchers at Harvard School of Public Health and the Dana-Farber Cancer Institute, and Case Western Reserve University School of Dental Medicine, for the first time, suggest a mechanism for how the microbe may cause cancer.

"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," senior study author Wendy Garrett of the Harvard School of Public Health and the Dana-Farber Cancer Institute said in a press release.

In the study led by Garrett the researchers found that fusobacteria are prevalent in a type of polyp called adenomas – benign tumors that can become malignant over time – suggesting that these microbes contribute to early stages of tumor formation. They found that these fusobacteria accelerate tumor formation by attracting immune cells called myeloid cells, which stimulate inflammatory responses that can cause cancer.

In the second study, researchers led by Yiping Han of Case Western found that a molecule, called Adhesin A (FadA) found on the surface of the fusobacteria sticks to and invades human colorectal cells. It then turns on cancer growth genes and stimulates inflammatory responses in these cells to stimulate tumor formation.

In addition, Han and her team found that FadA levels were much higher in tissues from patients with adenomas and colorectal cancer compared with healthy individuals, which makes FadA a potential early marker for colorectal cancer. Perhaps more importantly they identified a compound that can prevent FadA's effects on cancer cells. 

"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," Han says.