A new track arouses the interest of researchers to explain the increase in digestive cancers in those under 50. A toxin, produced naturally in the intestines, could play an unexpected role.
On April 23, 2025, a scientific study published in the journal Nature has highlighted an element potentially involved in certain cases of colorectal cancer. This factor, Colibactin, is a toxin produced by bacteria usually present in the body. This link between microbiota and illness poses new questions about how certain cancers can develop earlier than expected.
A major study to understand a worrying phenomenon
The study was conducted by a team from the University of California in San Diego. It relied on the analysis of 981 colorectal tumor genomes from patients distributed in eleven countries. The researchers have identified, in a large number of cases in young patients, precise mutations of DNA which seem to be linked to the presence of a bacterial toxin: Colibactin.
This toxin is produced by certain strains ofThey exhibited chilla bacteria that is naturally found in the intestines. According to researchers, it could cause damage to the genetic material of intestinal cells. Over time, these alterations could promote the appearance of abnormal cells, then tumors.
The results have shown that the traces left by this toxin were more frequent in people under the age of 40 with colorectal cancer, compared to those over the age of 70. This observation suggests that exposure to Colibactin could take place very early in life, sometimes even in childhood.
A toxin produced in our own microbiota
The particularity of this toxin is that it is produced by bacteria present in the human body. These particular strains ofE. coli have a group of genes, called ” pks “, Which allows them to make the Colibactin. It is therefore not a substance from the outside, but a compound generated directly in the intestines.
Colibactin is capable of damaging the DNA of the cells with which bacteria are in contact. These damage can be repaired by the body, but if they are not, they can accumulate and lead to mutations. Over time, these changes can promote the development of cancer.
-This link between intestinal toxin and colorectal cancers does not mean that all people carrying these bacteria will develop the disease. It is a possible risk factor among others. However, the discovery draws the attention of scientists to the role of the intestinal microbiota, that is to say all the microorganisms that live in our digestive system.
A global trend that alerts healthcare professionals
For the past twenty years, doctors have observed a regular increase in the number of colorectal cancers in young adults. In France, around 47,000 people are diagnosed each year, and colorectal cancer is the second cause of cancer death. Among 15-39 year olds, the rate of new cases increased on average by more than 1 % per year between 2000 and 2020.
This trend is also found abroad. About twenty countries, including the United States, the United Kingdom, Chile or New Zealand, recorded a similar increase. This phenomenon often affects patients who do not present the usual risk factors, such as poor diet, alcohol consumption or smoking.
It is precisely this lack of obvious explanation that led the researchers to explore other avenues. The potential role of Colibactin would provide a partial response to this case increase, especially among young people who do not yet have the recommended age to carry out regular screenings.
Results to be confirmed, but a serious track
Even if the results of this study are deemed solid, the researchers remain cautious. For the moment, it is an association: the mutations observed are typical of those that the Colibactin can cause, but this does not prove that this toxin is at the direct origin of cancers.
Other research will be necessary to understand how toxin acts, under what conditions it is produced, and why some people are more exposed than others. It will also be necessary to determine whether prevention measures can be envisaged, for example by monitoring the presence of these bacteria in young children or by developing targeted treatments against this toxin.
There are already tracks. Some scientists work on means of blocking the production of Colibactin by bacteria, or modifying the microbiota to reduce the presence of these special strains. Others are thinking about detection tests to know if a person has been exposed to this toxin.
