Cause of colon cancer might not be what we thought

Image colon polyp Wikimedia Commons

The cause of colon cancer might not be dietary or just hereditary. New research suggests polyps of the colon that lead to colon cancer could be caused in part by two specific types of  bacteria.

The finding has implications for how colon cancer begins and could mean new ways to prevent the disease that is the second leading cause of cancer death in the United States. (1)

Two types of bacteria play role in inherited and sporadic colon cancer

Researchers at Johns Hopkins made the discovery that two types of bacteria play a "critical role" in the development of  hereditary and sporadic cancer of the colon, based on observations that people with colon cancer harbor two types of intestinal bacteria.

The finding is also supported by studies in mice.

The two types of bacteria noted in people with cancer of the colon that seem to promote the formation of colon tumors are Bacteroides fragilis and Escherichia coli/

The combination of the two bacteria, which came as a surprise to researchers given the that there are more than 500 types of bacteria in our intestines, appears to promote inflammation that leads to DNA mutation and colon cancer.

Cynthia Sears, MD previously found the bacteria invaded the lining of colon in half of patients with colon cancer who had no hereditary risk for the disease.

Most bacteria in the intestines don’t do that because the colon has a protective mucous layer. These two bacteria form a biofilm that invades the colon.

Bacteroides fragilis and Escherichia coli combined produce a toxin that sets off a series of events including inflammation of the epithelial cells and gene alteration that leads to cancer.  
FAP, familial adenomatous polyposis,  occurs in approximately 5 percent of colon cancer patients. Sears wanted to know if bacteria could play a role in inherited colon cancer.

“If further research shows that biofilms develop before polyps appear, Sears says, adding biofilm evaluation or stool identification of particular bacteria to care could also provide an opportunity for earlier, nonsurgical intervention that could bump the bacteria from the colon.”

It’s possible that probiotics, a vaccine or drugs could stop the bacteria from colonizing. The researchers also say they want to know more about the immune system’s role in the inflammation caused by the bacteria that destroys DNA and leads to colon cancer.

The finding suggests bacteria could play an important role in colon cancer and could potentially change the way doctors screen for the disease as well as finding new ways toward prevention.