Mouth Bacteria May Help Cancer Spread by Making Cells Communicate

Bacteria that live in our mouths may help colorectal cancer spread by making cells effectively communicate with one another, according to a study.

As the bacteria travels through our blood vessels, a co-author of the study told Newsweek the findings suggest that keeping our mouths clean may help keep the germ known as Fusobacterium nucleatum (F. nucleatum) at bay.

F. nucleatum has previously been associated with worsening colorectal cancer. It is also found inside colorectal cancer cells that have metastasized, or spread to other parts of the body.

To conduct the study, researchers grew the bacteria alongside colorectal cancer cells and healthy immune cells in a lab. When F. nucleatum infected the cells, they gave off two proteins. The proteins, IL-8 and CXCL1, have previously been linked with poor outcomes in cancer patients, Daniel J. Slade, assistant professor in the College of Agriculture and Life Sciences at Virginia Tech told Newsweek.

The release of these proteins led tumor cells, regardless of whether they were infected themselves, to spread in the culture. This could be compared to the proteins leading the cancer cells to talk or communicate, Slade said.

By invading colorectal cancer cells, the mouth bacteria may therefore help the disease metastasize, according to the findings, published in the journal Science Signalling.

When the team exposed the cells to a type of sugar, this was found to stop the proteins from being let off, and prevented the germ from entering the cancer cells.

Slade said the team were inspired to carry out their study by a 2017 paper. That team implanted colorectal tumors in mice, and found those carrying F. nucleatum were able to metastasize and reattach in the liver.

"We feel this study is significant because it shows that a human oral bacterium is capable of inducing cancer cell metastasis, which is responsible for approximately 90 percent of cancer deaths."

But more research is needed on this topic before it can be used to help patients. Slade said: "As of right now there are no antibiotics or vaccines specifically targeting this bacterium, so we must proceed with caution when potentially treating these infections in cancer with broad spectrum antibiotics that could disrupt a healthy microbiome. Finally, we still need to continue this research to determine at the mechanistic level how this bacterium is accelerating cancer and metastasis."

The take-home message, Slade said, is that "people can potentially avoid infections by maintaining good oral health, which could in turn keep the levels of Fusobacterium nucleatum in the dental plaque under control."

Professor Jacques Neefjes, head of the department of cell and chemical biology at the University of Leiden in The Netherlands who did not work on the paper, told Newsweek via email the bacteria the team studied are difficult to grow and few labs can test their effects as the study did.

"Cancer is a multistep process," said Neefjes. "Salmonella—for example—contributes to one step and can make cells that have already made two steps on the way to cancer genuine cancer cells. The next step is metastasis formation which is the result of cell migration. This study contributes to this step in cancer."

Echoing Slade, Neefjes said the study may provide further motivation to people to take care of their teeth. "If confirmed in further studies, specific antibiotics may be included in toothpaste to eliminate these bacteria. But then we should first know how much these bacteria contribute to cancer formation."

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A stock image shows a scientist examining a culture of bacteria. Scientists believe mouth bacteria could help colorectal cancer to spread. Getty