How do oral bacteria make colorectal cancer more aggressive?
Scientists have identified a molecular mechanism through which an oral bacterium accelerates colorectal cancer growth.
Tests have shown that around a third of people who develop colorectal cancer also have the bacterium, which has the name Fusobacterium nucleatum. Their cancer also tends to be more aggressive, but it was not clear why until the recent study.
A paper that now features in the journal EMBO Reports reveals how the microorganism promotes the growth of cancer cells but not that of noncancerous cells.
The findings should help to clarify why some colorectal cancers develop much faster than others, say the researchers who hail from Columbia University in the City of New York.
The team also identified a protein that could form the basis of a test for more aggressive cancers and could lead to new treatments for colorectal and other cancers.
Colorectal cancer and its development
According to figures from the American Cancer Society, around 1 in 22 men and 1 in 24 women in the United States will receive a diagnosis of colorectal cancer at some point in their lives.
At the start of 2016, there were approximately 1.5 million people in the U.S. with a history of colorectal cancer, some of whom were cancer free.
Colorectal cancer develops from uncontrolled growth and survival of abnormal cells in the colon or rectum, which are the final sections of the digestive, or gastrointestinal, tract.
The colon absorbs water and nutrients from what is left of food after it has traveled through the stomach and small intestine. It then passes the remaining waste to the rectum, which stores it ready for expulsion through the anus.
The most common precancerous stage of colorectal cancer is a polyp, which is a growth that develops in the tissue that lines the colon and rectum. Polyps grow very slowly, sometimes taking 20 years to develop.
Most polyps develop from cells that make up the glands that produce a lubricating mucus in the colon and rectum. For this reason, they have the name adenomatous polyps, or adenomas.
Adenomas are very common, and around 33–50 percent of people will develop at least one. However, while they can all become cancerous, less than 10 percent actually become invasive.
