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Specific bacterium linked to colorectal cancer

Kathleen Blanchard's picture
Colorectal cancer linked to Fusobacterium bacterium

High numbers of Fusobacterium found in colon cancer tumors

In an intriguing finding, researchers have linked a specific bacterium to colorectal cancer. Two separate teams of researchers have discovered high numbers of Fusobacterium in tumors of patients with colon and rectal cancer. The bacterium is pathogenic and linked to several diseases, including ulcerative colitis.

The research finding, which appears in the journal Genome Research, is the first to find any link between bacteria and colorectal cancer.

Researchers sequenced DNA from nine colon cancer tumors. They compared their finding to DNA in normal colon tissue, finding the high number of Fusobacterium only in colorectal cancer tumors.

Scientists from the BC Cancer Agency and Simon Fraser University in Canada report similar findings, after sequencing normal colon RNA and matching it with 11 colorectal cancer tissue samples.

They specifically found the Fusobacterium nucleatum bacterium, which is considered a mouth pathogen.

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Senior study author, Matthew Meyerson, MD, PhD, of Dana-Farber and the Broad Institute said, “Tumors and their surroundings contain complex mixtures of cancer cells, normal cells, and a variety of microorganisms such as bacteria and viruses.

Over the past decade, there has been an increasing focus on the relationship between cancer cells and their ‘microenvironment,’ specifically on the cell-to-cell interactions that may promote cancer formation and growth.”

Meyerson says the researchers aren’t clear what role Fusobacterium plays in the development of colorectal cancer. They’re not ready to say colorectal cancer is caused by bacteria. It may be the cancer provides a welcome environment for the bacteria to flourish.

Researchers know inflammation that accompanies infection and other diseases can lead to cancer.

Richard Stein, writing in the Journal of the American Medical Association in April 2011 suggested bacteria may lead to changes in the way genes are expressed to promote cancer. He recommended more research on the role of bacteria and viruses as a cause of cancer.

Stein said, “Today, “20% of cancers have been causally linked to human pathogens”, citing Epstein-Barr virus that is linked to cancer of the nose and throat and affects 90 percent of the population.

The researchers are planning studies in mice to see if Fusobacterium induces cancer. They are also continuing studies in larger numbers of patients with and without colorectal cancer.

Image credit: Morguefile