Saliva does more than just break down your lunch. It could be key to screening for pancreatic cancer too.

The notoriously aggressive cancer has received a lot of publicity in recent years with the deaths of Patrick Swayze and Steve Jobs, both of whom suffered from the disease.

Now, researchers have found that looking for certain bacteria in the mouth could lead to earlier diagnoses and save lives.

A team led by James Farrell of the University of California, Los Angeles, compared the bacteria in the mouths of 10 healthy people with those in 10 people with pancreatic cancer. They found significant differences in the microbe populations in each group.


These changes could be used to trigger a check for pancreatic cancer. “It’s the canary in the coal mine, an early-warning signal,” says Bruce Paster at the Forsythe Institute in Cambridge, Massachusetts, who worked with Farrell to identify the bacteria in the samples. “If you have a disease [such as cancer], it’s not usually just restricted to the pancreas or the intestine. Your whole body is affected – things change,” he says.

Locked out

In this case, changes occurred to the epithelial cells that line cavities in the body, including the mouth. These cells contain receptors that accept certain bacteria only – like a lock waiting for the right key. When a bacterium with the correct-shaped key – called an adhesin – comes by, it attaches itself to the corresponding epithelial cell. “Good” bacteria like this provide us with a shield against more unpleasant, disease-causing microbes.

The epithelial cells of people with pancreatic cancer seem to change shape, allowing more bad bacteria to take up residence in the mouth. Out of the hundreds of bacteria that live there, two species that are usually abundant in a healthy mouth – Neisseria elongata and Streptococcus mitis – were significantly scarcer in people with pancreatic cancer.

Farrell says that the team cannot be sure if the bacterial population shift is a cause or effect of the cancer. “We cannot conclude that [certain bacteria in the mouth] makes someone more likely to develop pancreatic cancer,” says Adam Roberts, a molecular microbiologist at University College London.

But he says that the finding is an important step towards quick, non-invasive screenings for this and other diseases. “The possibility of being able to screen spit for certain bacteria to predict cancer is a really attractive proposition. It would result in early detection, which would inevitably save lives.”

Farrell is validating his findings with a larger group of volunteers with the intention of creating such a tool. Paster is also working with Michael Docktor at the Forsythe Institute and Athos Bousvaros at the Children’s Hospital Boston to identify other diseases, such as Crohn’s disease, where changes in oral bacteria may act as a diagnostic tool.

Journal reference: Gut, DOI: 10.1136/gutjnl-2011-300784