Exposure to a bacterial toxin in childhood may be playing a key role in the global rise of early onset of colorectal cancer, according to a new study.
The study, published April 23 in Nature, found that a toxin called colibactin, produced by certain strains of E. coli that live in the colon and rectum, is capable of altering DNA.
The researchers from the University of California reported that early exposure to colibactin leaves a unique mark on colon cell DNA — one that could bump up your chances of getting colorectal cancer before 50.
However, it’s important to note that the study did not prove colibactin caused cancer, it only identified a link between mutations linked to the toxin and early-onset disease.
“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,” said study senior author Ludmil Alexandrov, professor in the department of cellular and molecular medicine at the University of California San Diego.
“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,” he said in a media release.
Colorectal cancer includes two types of cancers: cancer of the colon and cancer of the rectum.
Generally, it spreads more slowly than many other cancers, often lingering in the colon or rectum for months or even years before spreading elsewhere. That means if it’s detected early, treatment is usually very effective.
While colorectal cancer rates have been falling among older adults, they’ve been climbing in people under 50 — both in Canada and around the world — over the past few decades, for reasons that still aren’t clear.
If current trends continue, it’s projected to become the leading cause of cancer-related death among young adults by 2030.
“The fastest-growing subset of the population who get colorectal cancer, and primarily rectal cancer, are between the ages of 28 and 39 years old,” said Barry Stein, president and CEO of Colorectal Cancer Canada.
“And we don’t have a reason to understand why these people are being diagnosed or why they’re getting colorectal cancer in the first place.”
The question of why this is happening is what led the University of California researchers to dig deeper. Stein explained that there’s already some evidence linking gut bacteria to colorectal cancer — whether it’s a cause or just a correlation — and said this study adds another piece to the puzzle.
●What the study found
To help explain the medical mystery, the study’s researchers looked at 981 colorectal cancer genomes from patients with both early- and late-onset disease across 11 countries (including Canada) with varying colorectal cancer risk levels.
The researchers found that colibactin leaves behind DNA mutation patterns in colorectal cancer that are 3.3 times more common in adults diagnosed before 40 than in those diagnosed after 70, and these patterns are especially frequent in countries with high rates of early-onset colorectal cancer.
Previous studies, including earlier work from Alexandrov’s lab, have found colibactin-related mutations in about 10 to 15 per cent of all colorectal cancer cases.
Bu, these studies either focused on late-onset cases or didn’t differentiate between early- and late-onset disease. This latest study is the first to specifically highlight a significant increase in colibactin-related mutations in early-onset cases, the researchers said.
source: Global News photo: Wikipedia
