Humanity

Colibactin is produced by bacteria commonly found in the digestive system, including certain types of E. coli. About 20% of healthy people—and even some 31% of babies—have colibactin-producing E. coli in their guts, previous studies estimate.67

The toxin is known to damage DNA, and previous studies have suggested that colibactin-related mutations contribute to some cases of colorectal cancer.8

Dziubańska-Kusibab PJ, Berger H, Battistini F, et al. Colibactin DNA-damage signature indicates mutational impact in colorectal cancer. Nat Med. 2020;26(7):1063-1069. doi:10.1038/s41591-020-0908-2 But Ludmil Alexandrov, PhD, a professor of cellular and molecular medicine at the University of California, San Diego and senior author of the new study, didn’t set out to research colibactin specifically.

Originally, his team wanted to understand why people in different countries develop colorectal cancer at different rates. They genetically analyzed almost 1,000 colorectal cancer samples from people living in 11 countries to compare and contrast them.

“We did find some results which were country-specific,” Alexandrov said. “But actually, the thing that we found most exciting was this colibactin result.”

Alexandrov’s team found that DNA mutations associated with colibactin were 3.3 times more common in cancers diagnosed before age 40, compared to those diagnosed after age 70. They estimated that colibactin exposures likely happened early in study participants’ lives—probably before their 10th birthdays.

The results suggest that colibactin exposure could “put children on a trajectory for developing colorectal cancer 20 or 30 years earlier [than normal]—so instead of getting it at the age of 60 or 70, they’re getting it at the age of 30 or 40,” Alexandrov explained.