Colorectal tumors exacerbated by mouth microbes

Mouth microbes called fusobacteria may use the bloodstream to reach and worsen colorectal tumors through a special sugar-binding protein, study finds.

Colorectal cancer is the third leading cause of cancer-related deaths in the United States when men and women are considered separately, and the second leading cause when both sexes are combined.

While the death rate from colorectal cancer has decreased in both males and females – due to colorectal polyps being found by screening and removed before they can develop into cancer – not enough people are getting screened for colorectal cancer. In 2014, 65.7 percent of U.S. adults were up-to-date with colorectal cancer screening; 7 percent had been screened, but were not up-to-date, and 27.3 percent had never been screened. Previous studies by the Garrett Lab at the Harvard T.H. Chan School of Public Health in Boston, MA, have shown fusobacteria to promote the formation of colorectal tumors and exacerbate colorectal cancer in animals. Also, they found that fusobacteria are enriched in human colorectal tissue when compared with neighboring healthy tissue. According to the Harvard researchers and scientists from the Hebrew University-Hadassah School of Dental Medicine in Israel, this is the first study to shed light on how the microbes from the mouth make their way to the gut, and how they localize to and become abundant in colorectal tumors.

The findings, published in Cell Host & Microbe, demonstrate that fusobacteria use a sugar-binding protein to stick to developing colorectal polyps and cancers, whereby they proliferate and subsequently accelerate the disease.

“As fusobacteria contribute to colon tumor development, revealing the mechanism that guides them to the tumor and why fusobacteria become abundant there might inform ways of blocking this,” says co-senior author Wendy Garrett, of the Harvard T.H. Chan School of Public Health and the Dana-Farber Cancer Center.

“Alternatively, and perhaps more importantly, if we know how fusobacteria localize and become enriched in colon tumors, hopefully, we can utilize the same or similar mechanisms to guide and deliver cancer therapeutics to colon tumors,” she adds.

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