Colorectal cancer risk could rise with exposure to toxin during childhood

April 25, 2025

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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.

See also Rep. Alexandria Ocasio-Cortez’s tough Bronx persona is under fresh scrutiny with a resurfaced childhood nickname from her suburban upstate New York upbringing casting doubt on that publicly portrayed image. The progressive champion’s latest spat with President Donald Trump over the Iran strikes again called into question her true upbringing when she declared on X she was a “Bronx girl" to make her a point against the president. The 35-year-old congresswoman wrote in part on X: "I’m a Bronx girl. You should know that we can eat Queens boys for breakfast. Respectfully," she said, referring to the president’s upbringing in Queens as she called for his impeachment over his decision to bypass Congress in authorizing U.S. strikes on Iranian nuclear facilities. Ocasio-Cortez was born in the Bronx but moved to Yorktown – which is nearly an hour outside New York City -- when she was 5 years old and went on to attend Yorktown High School where she graduated in 2007. She was considered an accomplished student there and well thought of by teacher Michael Blueglass, according to a 2018 report by local media outlet Halston Media News. “There, known by students and staff as ‘Sandy,’ she was a member of the Science Research Program taught by Michael Blueglass," the report states. “She was amazing," Blueglass said, per the report. “Aside from her winning one of the top spots and going to the [Intel International Science and Engineering Fair], she was just one of the most amazing presenters in all of the years I've been at Yorktown. Her ability to take complex information and explain it to all different levels of people was fantastic." After high school, Ocasio-Cortez attended Boston University, where she majored in economics and international relations, per the report. Ocasio-Cortez’s “Sandy" nickname — which carries a more suburban and preppy tone — appears to undercut her politically crafted image as a tough, inner-city fighter, one she has portrayed since her famous 2018 congressional campaign where she eventually ousted former 10-terms Congressman Joe Crowley. New York GOP Assemblyman Matt Slater, who now represents Yorktown, added to the scrutiny of Ocasio-Cortez’s persona in the wake of her brash with Trump and released images of Ocasio-Cortez from his high school yearbook. He claimed he and the rising Democratic star attended Yorktown High School at the same time when she was a freshman and he was a senior. "I saw the attacks on the president and her [Ocasio-Cortez] claims that she's a big, tough Bronx girl," said Slater. "To sit there and say that she’s a Bronx girl is just patently ridiculous." "Everybody in our community knows this is just a bold-face lie," said Slater on "Fox & Friends First" last week. "She grew up in Yorktown, she was on my track team." "She's lying about her background, she's lying about her upbringing," Slater claimed. Slater’s post sent social media ablaze and prompted Ocasio-Cortez to respond after an image if her family’s home was posted online. “I’m proud of how I grew up and talk about it all the time," Ocasio-Cortez wrote on X Friday responding to the post. “My mom cleaned houses and I helped. We cleaned tutors’ homes in exchange for SAT prep." “Growing up between the Bronx and Yorktown deeply shaped my views of inequality & it’s a big reason I believe the things I do today!"

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.”

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“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.