Colorectal cancer risk could rise with exposure to toxin during childhood

Amid the alarming trend of colorectal cancer cases rising among young people, a new study has pinpointed a potential source. Researchers from the University of California San Diego have linked a bacterial toxin called colibactin to the increase in early-onset cases. Colibactin is produced by certain strains of Escherichia coli (E. coli) that exist in the colon and rectum, according to the researchers.

Exposure to the bacterial toxin during early childhood can alter the DNA of colon cells in a way that increases the risk of developing colorectal cancer before age 50, the study found. In the study, the researchers analyzed 981 colorectal cancer genomes from early-onset and late-onset colorectal cancer patients across 11 countries.

Those who had prior exposure to colibactin were found to have specific mutations in their DNA, which have been shown to mainly occur in the first decade of life — “placing children on an accelerated path to developing cancer as young adults.” That group was 3.3 times more likely to develop early-onset colorectal cancer compared to those who were diagnosed after 70.

These mutations were found to make up 15% of the early genetic alterations that increase colorectal cancer risk. “We detected the mutational signature of colibactin in over 50% of colorectal tumors from patients under 40, compared to less than 10% in tumors from older individuals,” Alexandrov noted. “If someone acquires one of these driver mutations by the time they’re 10 years old, they could be decades ahead of schedule for developing colorectal cancer, getting it at age 40 instead of 60,” noted Alexandrov.

The fact that a microbial exposure in the first few years of life can leave a “lasting genomic imprint” and likely contribute to cancer in adulthood is both “remarkable and sobering,” according to the researcher. “It’s a reminder that there are likely many other such exposures we’ve yet to uncover, and that the way we nurture and protect children during these formative years may have long-term implications for their lifelong health,” he told Fox News Digital.

Dr. Emil Lou, MD, PhD, a board-certified oncologist and internal medicine physician at the University of Minnesota, agrees that the microbiome – “the constellation of microbes that includes bacteria that live under normal circumstances in our gut” — is one potential culprit of early-onset colorectal cancer. “It is less surprising now than it was a decade ago that any form of bacteria – more specifically, a toxin derived from bacteria – could be associated with and potentially be the primary cause of cancer,” Lou, who was not involved in the study, told Fox News Digital.

Alexandrov pointed out that the study provides “strong genomic evidence” of a “striking association” between colibactin and early-onset colorectal cancer, but cannot prove causation. “Demonstrating unequivocal causality — proving that colibactin alone is sufficient to initiate cancer in humans — remains a significant challenge,” he told Fox News Digital.

“Definitive proof of causality would require long-term prospective studies beginning in early childhood to monitor microbial colonization and track cancer development over several decades.” Lou agreed with this limitation, noting the complexity of cancer factors. “There are many aspects of our environment – both within and outside of our bodies – that can play a role in the development of cancer,” he said. “It is difficult to say or conclude whether any given single factor – in this case, the bacteria-derived toxin – is the true or even a major cause of colorectal cancer.”

“If current trends continue, colorectal cancer is projected to become the leading cause of cancer-related death among young adults by 2030,” the researchers concluded. Melissa Rudy is senior health editor and a member of the lifestyle team at Fox News Digital. Story tips can be sent to melissa.rudy@fox.com.