Could Cancer Spread be Driven by a Common Mouth Microbe?
An ordinary bacterium can trigger changes in some primary tumors that lead to dangerous metastasis.
Cancer can be frightening, in large part because of its potential to metastasize (spread to distant sites of the body). Metastases are associated with approximately nine out of every 10 deaths from cancer. Enter a new player: a common bacterium known as Fusobacterium nucleatum. Could this so-called harmless bacterium be a wolf in sheep’s clothing?
Let’s look at this microbe. F. nucleatum typically normally lives harmlessly in the gums of our mouths. In healthy individuals, this microbe serves as a helpful member of our microbial community. Now, it is being exposed as a potential villain; the bacterium may play a role in the spread of some cancer. Examples of malignancy include colon, esophagus, pancreas, and possibly breast cancer.
In its normal and more quiecent mode, the bacterium resides in the mouth. But, if you have poor dental hygiene or uncontrolled diabetes, the microbe can show its bad side. It can cause inflammation of the gums, tonsils, or the appendix. Now it gets even more interesting: The microbe can travel in our bloodstreams.
The microbe can attach to a cancer cell
The microbe attaches to a sugar molecule on the surface of a cancer cell. This sets off a cascade of signals and immune responses that result in tumor cell migration. Could F. nucleatum add to our understanding of how our microbiome influences cancer metastasis?
The answer may be yes: There appears to be a link between colorectal cancer and the presence of the bacterium’s DNA — the microbial DNA was more commonly found in colon tumors, compared with normal tissue. It gets more interesting — infection is associated with poorer outcomes among those with colorectal, esophagus, and pancreas cancer.
Association or causality?
You probably wonder whether the bacteria play a causal role, or rather is there simply an association with the aforementioned outcomes. Studies in mice suggest that the bacteria cause colon cancer cells to make proteins known as cytokines. These substances promote the migration of cancer cells. A separate laboratory study discovered the bacterium induces gene changes that lead to a higher probability of distant spread.
Hebrew University scientists found F. nucleatum DNA in 30 percent of the human breast cancer tissue, especially if the cells had a lot os a surface sugar molecule. They note that infection promotes the growth of the primary tumor and metastases, at least in mice. While the study authors don’t think the microbe is causing cancer, they think it might enhance progression, like gasoline on an existing fire.
Into the future
Could this happen in humans, too? Might an infection lead to a significant inflammatory reaction in a cancer cell, promoting it to be more mobile? We know that inflammation is associated with cancer cells. Keep an eye out on research examining the role of microbes in cancer behavior. I can imagine attaching a toxin to the microbe and using the bacteria as a delivery system to bring the bomb to the cancer cell.
I don’t know that there is anything actionable right now for me or you. A causal relationship between microbe and cancer has not been established. It does seem logical (and good manners) to maintain good dental hygiene.
Thank you for joining me today.