Colorectal cancer is increasingly affecting younger adults. Even as the disease remains more common in people over 50, the number of cases is steadily rising in those under 50, increasing by approximately 0.5% per year, according to research from the University of Geneva Hospitals. A team in California has investigated potential factors explaining this trend, identifying a microbial agent potentially driving the increase in early-onset colorectal cancers: colibactin, produced by certain strains of Escherichia coli.
Colibactin Linked to DNA Mutations in Colorectal Cancer
“Our initial goal was to examine global trends in colorectal cancer to understand why some countries have much higher rates than others,” explained Marcos Díaz-Gay, a co-author of the study. “But when analyzing the data, one of the most interesting and striking discoveries was the frequency of mutations linked to colibactin in cases of early-onset colorectal cancer.”
The research team analyzed 981 genomes of colorectal cancers from patients across 11 different countries. “The results show that colibactin leaves specific genetic fingerprints, with DNA mutations occurring 3.3 times more frequently in people diagnosed with early-stage disease – particularly those under 40 – compared to those diagnosed after age 70,” the authors found. These mutations were also particularly prevalent in countries with a high incidence of early-onset cases.
Early Exposure to Bacteria May Play a Role in Colorectal Cancer Development
Researchers suggest these DNA mutations could indicate that early exposure to colibactin is a key factor in the development of the disease. Previous studies have already identified links between colibactin and colorectal cancers, but its role in early-onset cases had not been studied. These earlier studies demonstrated that mutations linked to colibactin occur during the first ten years of life. “If a person acquires one of these driver mutations before the age of 10, they could develop colorectal cancer several decades earlier, at 40 instead of 60,” said lead author Ludmil Alexandrov. The bacteria that produce colibactin are capable of colonizing the colons of children, often without causing symptoms, but inducing molecular changes in DNA that could potentially lead to colorectal cancer later in life.
Future Test Could Reduce Risk of Early-Onset Cases
The study, largely conducted by researchers at the University of San Diego, has potentially concerning implications. “Once considered a disease of older adults, colorectal cancer is now increasing in young people in at least 27 countries,” the authors state. “Its incidence in adults under 50 has nearly doubled every ten years over the past two decades. If current trends continue, colorectal cancer is projected to become the leading cause of cancer death in young adults by 2030.”
The team is now investigating children’s exposure to colibactin-producing bacteria and exploring whether probiotic treatments could eliminate harmful bacteria to prevent DNA mutations. Simultaneously, scientists are developing screening tests to detect colibactin-linked mutations in stool samples. These developments could lead to earlier detection and intervention strategies for a disease that is becoming increasingly prevalent in younger populations, highlighting the importance of continued research and awareness.
