It’s fairly common knowledge that a long-term diet of high-fat red meat and a sedentary lifestyle can be a dependable recipe for colon cancer. 

But why? What is it about red meat or a high-fat diet that promotes cancer in the colon? And why is a lack of exercise such a risk?

Johns Hopkins researchers Cynthia Sears and Francis Giardiello are taking a look at the microbiome—the colony of trillions of bacteria that live in the human gut—for answers.

“The bacteria in the colon may be influenced by what you eat,” Giardiello says, “and that can give you certain populations of bacteria that then predispose you to colon cancer.”

So Sears, professor of medicine, oncology and molecular microbiology and immunology, and Giardiello, professor of medicine and former director of the Johns Hopkins Division of Gastroenterology, teamed up to focus on the coating of bacteria that sometimes sticks to the walls of the colon—biofilm—rather than looking at the bacteria that move through the colon. Does the sticky coating of bacteria that clings to the walls of our intestines play a role in cancer?

The pair was recently awarded a five-year, $4.3 million research grant from the National Institutes of Health for the first-ever comprehensive study of the colon’s biofilm as it relates to cancer. Among their goals: Determine just how the triggers—a carnivorous diet, smoking, obesity, diabetes, chronic colitis, a lack of exercise—contribute to the gut environment that can lead to colon cancer.

The Sears laboratory identified that all cancers from a certain part of the colon show biofilms and that bacteria were stuck in layers in these cancers.

“We suspect that biofilm formation increases cancer risk and can be a very early cancer marker,” Sears says. “The goal is always to catch it as early as possible.”

If their hypothesis is proved, Giardiello and Sears will have discovered the earliest-ever marker in the progression of colon cancer.

The landmark study began in August. Two thousand patients undergoing routine screening colonoscopies at four sites in Maryland and Pennsylvania will be asked to volunteer for the study.

“We are going to evaluate these patients going through colonoscopy,” Giardiello says, “checking for these biofilms in their colon in work done in the Sears laboratory, and see if they associate with colon cancer or polyps.”

Giardiello says 141,000 Americans a year get colon cancer. And every year, 50,000 people die in the U.S. of the disease. While genetics plays a role, he estimates that 70 to 80 percent of colon cancer cases are the result of a poor diet and not enough physical exercise.

Giardiello and Sears also plan to study the biofilm’s durability.

“If you find it once in, say, January and then rescope the patient in July, are the biofilms still there? And are they the same? Are they durable?” he asks. “If that’s the case, then that also could be a biomarker for colon cancer risk.”

Sears’ previous research has found that certain Bacteroides fragilis—a common gut bacteria—can be, in large numbers, particularly noxious to the lining of the colon.

“The bacteria are causing inflammation,” she says. “And that inflammation can lead to cancer.”