Bacteria found in the mouth that typically lead to gum disease can also cause colon cancer, two new studies have found.
Fusobacteria can cause an overreaction in the immune system and trigger "cancer growth" genes, according to researchers at Harvard Medical School and Case Western Reserve University.
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The microbes have been linked with colon cancer before.
But it was not known whether they were directly involved in tumor growth until this latest research published in the journal Cell Host & Microbe.
Experts hope the findings could lead to new treatments, as well as earlier diagnosis and prevention.
The first study by Harvard researchers showed high levels of fusobacteria in adenomas, benign bowel growths that can turn cancerous over time.
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In the second study, Case Western scientists found a molecule called FadA on the surface of fusobacteria that enabled them to attach to and invade colon cancer cells in the human body.
"I think we all need to be concerned, because almost everyone has Fusobacterium to some extent," Yiping Han, a periodontics professor at Case Western, told the Cleveland Plain Dealer. "We need to do more work"
Colon cancer is the second-leading cause of cancer-related death in the United States, according to the Centers for Disease Control and Prevention. In 2009, the most recent data available, 136,717 people in the United States were diagnosed with the disease.