Will Stone, NPR 4/25/25: Damage from gut bacteria may play a role in the rise in colon cancer in young adults

An excerpt:

It’s unclear why colon cancer cases have doubled in people under 55 over the past two decades, a staggering rise that has alarmed doctors and cancer researchers.

But part of the story could be colibactin, a toxin made by certain strains of E. coli and other bacteria. In a study out this week, researchers have identified a strong link between this DNA-damaging toxin and colon cancer among younger patients.

The team, based at the University of California, San Diego, analyzed tissue samples from close to 1,000 colorectal cancer patients across four continents. They found the majority had cancers bearing mutations that signaled a past encounter with colibactin.

“You can think of it as the weapon system of a bacteria to fight other bacteria and to defend themselves,” says Ludmil Alexandrov, the lead author of the study, which was published in Nature this week.

Strikingly, those under the age of 40 with early-onset colon cancer were three to five times more likely to have these mutations than those in their 70s and older.

The thinking goes that in some people, this bacterial weaponry — technically called a “genotoxin” — can get directed at their gut cells, seeding mutations that put them at increased risk of developing colorectal cancer.

According to their data, this exposure isn’t ongoing when the cancer is diagnosed. Instead, it appears to have happened during childhood.

“Our estimate is that it happens within the first 10 years of life,” Alexandrov says. “So if you get that mutation at age 5, that puts you 20 to 30 years ahead of schedule for getting colorectal cancer.”

While the study shows a strong association, the data can’t prove colibactin caused these patients to develop cancer at a younger age. And researchers in the field don’t expect E. coli, or any single microbe for that matter, to be the skeleton key for the surge in colorectal cancer.

Related article: M Diaz-Gay, et al. Nature https://doi.org/10.1038/s41586-025-09025-8 (2025). Geographic and age variations in mutational processes in colorectal cancer

Related blog posts:

• Colorectal Cancer in Patients Up to Age to 25 Years
• Colorectal Cancer: Rare in Pediatrics
• Surprising Genetic Mutations in Polyposis Study
• What I Like About ESPGHAN Familial Adenomatous Polyposis Guidelines 
• Three Tweets: Colon Cancer Screening at 45 years (American Cancer Society 2018 Recommendation)
• Colon Cancer at Younger Ages
• Five Ways to Lower the Risk of Colorectal Cancer
• Diet, Meat, and Colorectal Cancer