Is the rise in early-onset colorectal cancer linked to childhood exposure to a bacterial toxin? A groundbreaking study published in Nature on April 23, 2025, reveals a potential culprit behind the alarming increase in colorectal cancer cases among young adults: colibactin, a bacterial toxin produced by certain strains of Escherichia coli. This research, led by the University of California San Diego, suggests that early childhood exposure to colibactin leaves a distinct genetic signature on colon cells, potentially increasing the risk of developing colorectal cancer before the age of 50.
For years, scientists have been baffled by the growing incidence of colorectal cancer in individuals under 50. While the disease was once primarily associated with older adults, its prevalence among younger people has been doubling every decade for the past 20 years. By 2030, colorectal cancer is projected to become the leading cause of cancer-related deaths in young adults, fueling an urgent need to understand the underlying causes. This new study provides a crucial piece of the puzzle.
The international research team analyzed nearly 1,000 colorectal cancer genomes from patients across 11 countries, comparing early-onset cases (diagnosed before age 40) with late-onset cases (diagnosed after age 70). The findings revealed that colibactin-related DNA mutations were 3.3 times more common in early-onset cases, especially in countries with a high incidence of the disease in young adults.
"These mutation patterns are a kind of historical record in the genome, and they point to early-life exposure to colibactin as a driving force behind early-onset disease," explained Professor Ludmil Alexandrov, senior author of the study.
The study further suggests that colibactin's damaging effects begin early in life. Researchers determined that colibactin-associated mutations arise within the first 10 years of life and account for approximately 15% of APC driver mutations, some of the earliest genetic alterations that promote cancer development.
"If someone acquires one of these driver mutations by the time they're 10 years old," Alexandrov explained, "they could be decades ahead of schedule for developing colorectal cancer, getting it at age 40 instead of 60."
While the findings are compelling, researchers caution that further investigation is needed to establish causality. They are now focusing on identifying how children are exposed to colibactin-producing bacteria and exploring potential preventative measures, including the use of probiotics to eliminate harmful bacterial strains. Additionally, they are developing early detection tests to analyze stool samples for colibactin-related mutations.
The study also uncovered geographic variations in mutational signatures, suggesting that other local environmental exposures may contribute to colorectal cancer risk in specific countries, such as Argentina, Brazil, Colombia, Russia, and Thailand.
This research underscores the possibility that many cancers may originate from environmental or microbial exposures in early life, reshaping our understanding of cancer development and highlighting the importance of sustained investment in research focused on early prevention and treatment strategies.
