Childhood Exposure to Bacterial Toxin Linked to Increased Risk of Early-Onset Colorectal Cancer

Recent research from the University of California, San Diego, has shed light on a possible microbial cause behind the rising incidence of colorectal cancer among young adults. An international team of scientists has identified a bacterial toxin called colibactin, produced by specific strains of Escherichia coli residing in the colon and rectum, as a potential contributor to early-onset colorectal cancer.

Colibactin is capable of damaging DNA, and exposure to this toxin during childhood appears to imprint distinct mutational signatures onto colon cell DNA. These genetic alterations are significantly more prevalent in cases of colorectal cancer diagnosed before age 50, especially in individuals under 40, compared to older patients. The study analyzed 981 tumor genomes from patients across 11 countries with varying risk levels, revealing that 3.3 times more mutation patterns associated with colibactin were present in early-onset cases.

Senior author Ludmil Alexandrov explained that these mutation patterns serve as historical records, indicating that early-life exposure to colibactin may play a critical role in the development of colorectal cancer decades later. The findings also showed that these mutations are an early event in tumor formation, occurring within the first 10 years of life, and contribute to approximately 15% of key driver mutations in colorectal cancer.

Colorectal cancer was traditionally viewed as a disease primarily affecting older adults, but its incidence among young people has nearly doubled each decade for the past 20 years. Currently, in over 27 countries, cases in individuals under 50 are on the rise, and projections suggest it could become the leading cause of cancer-related death in young adults by 2030.

The study investigates environmental and microbial exposures as possible reasons for this trend, especially since many young patients have no common risk factors like obesity or family history. The researchers suggest that bacteria producing colibactin may silently colonize children’s intestines, initiating molecular changes that predispose them to cancer much earlier than previously thought.

Further research aims to determine how children are exposed to colibactin-producing bacteria, whether certain environments or behaviors increase exposure, and if interventions like probiotics or early detection tests can reduce risk. The team is also exploring regional variations in mutational signatures, indicating that local environmental factors could influence cancer risk.

This new understanding emphasizes the importance of early-life microbial and environmental influences on cancer development, prompting a shift in how we approach prevention and early detection strategies for colorectal cancer and potentially other cancers originating from microbial exposures during childhood.

Source: Medical Xpress