The bacterium found in higher numbers is the oral pathogen Fusobacterium nucleatum. In the past the bacterium has been linked to periodontal diseases (various diseases of tooth-supporting structures.) This microorganism, which is commonly found in the mouth’s of people, is found in higher numbers in people suffering from certain forms of cancer. It appears that the bacterium protects a variety of tumor cells from being killed by the body’s immune cells (so-termed “natural killer cells.”) In a sense, the bacterium provides tumor cells with a protective, shell-like defense mechanism against the body’s own immune system.
This makes more sense if the way the immune cells work is considered. To function, immune cells need to bind to the target site. The bacterium secretes a protein that inhibits this function. Having understood this, the scientists aim to find out how many types of tumor the bacterium is associated with. They also wish to see if any other types of bacteria are involved.
The cancer that has the strongest association with the bacterium is colon cancer. Risk factors for colorectal cancer include lifestyle, older age and inherited genetic disorders. In addition, there is an association with diet, smoking, alcohol, lack of physical activity, presence of colon polyps, exposure to radiation, and obesity.
In terms of the research implications, it is possible that new anti-cancer treatments could emerge. Scientists think that by blocking the interaction between the bacteria and immune cells, then existing cancer medicines may function better.
The study was performed at the Hebrew University-Hadassah School of Dental Medicine. The findings have been published in the journal Immunity. The research study is titled “Binding of the Fap2 Protein of Fusobacterium nucleatum to Human Inhibitory Receptor TIGIT Protects Tumors from Immune Cell Attack.”
