Rise in colon cancer among young people may be tied to gut toxin known to cause DNA damage

A gut toxin that’s been linked to colorectal cancers for more than two decades may be to the sharp rise of the disease in younger people, according to new research.

A gut toxin that’s been linked to colorectal cancers for more than two decades may be contributing to the sharp rise of the disease in younger people, according to landmark research published Wednesday in the journal Nature.

A number of species of harmful gut bacteria — including certain strains of E.coli, Klebsiella pneumoniae and Citrobacter koseri — produce a toxin called colibactin. Since the mid 2000s, studies have repeatedly shown that this toxin can inflict distinct DNA damage on colon cells that’s difficult to repair and can eventually lead to the development of cancer. 

That DNA damage is particularly prominent in people who developed colorectal cancer at a younger age, researchers at the University of California San Diego said Wednesday. The new study sequenced the DNA of colorectal cancer tumors collected from 981 patients in 11 countries around the world, and found that colibactin-related DNA mutations were 3.3 times more common in patients under the age of 40, compared with those over 70. 

“Around 50% of early-onset colorectal cancers in individuals under 40 carried the distinctive signature of colibactin exposure,” senior study author Ludmil Alexandrov, a bioengineering and cellular and molecular medicine professor at UC San Diego, said in an email interview.

The finding could have critical implications for public health amid rising rates of colorectal cancer in young people. Two years ago, the American Cancer Society reported that colorectal cancer diagnoses in patients under 55 had doubled between 1995 and 2019, with rates of advanced disease now increasing by roughly 3% every year in people younger than 50. Christopher Johnston, associate professor and director of microbial genomics at MD Anderson Cancer Center, described the connection to colibactin as being potentially crucial to explaining this alarming trend.