Certain intestinal bacteria are found more frequently in countries such as Norway than in a number of other countries and there is also a higher incidence of bladder cancer, bowel cancer and prostate cancer. These findings may lead to new opportunities for preventing these types of cancer, according to a new study.
Previous studies have shown that a toxin produced by certain bacteria in order to dominate inside the intestine, causes damage to healthy cells and increases the risk of developing bowel cancer.
In a new study, scientists examined incidence of bladder, colon, rectal and prostate cancer and compared this to the prevalence of two toxin-producing E.coli bacteria in the countries concerned. E.coli is the most common cause of urinary tract infections and bacterial infections in the bloodstream worldwide.
Norway has a higher incidence of bladder cancer and colorectal cancer compared with many other countries.
– In the course of the study, we also found that the prevalence of these two E.coli bacteria was higher in Norway. When we compared equivalent data from several different countries, we discovered a clear pattern: the fewer of these E.coli bacteria that circulate in the population, the lower the incidence of these types of cancer, and vice versa, explains Jukka Corander, professor at the Department of Biostatistics at the Institute of Basic Medical Sciences, UiO, and leader of the study recently published in Lancet Microbe.
Can destroy DNA in cells
In recent years, intense research has been carried out internationally on the link between the toxin produced by these bacteria, called colibactin, and several types of cancer. The research was initiated after groundbreaking studies revealed that colibactin damages DNA in intestinal cells and where scientists produced models of intestinal organs and saw that the toxin-producing E.coli resulted in cancer in the models.
In this new study, the team used a new method of analysis, developed by the research scientist Tommi Mäklin, in collaboration with Corander.
The scientists discovered that a certain subtype of E.coli had developed a stable relationship with these harmful colibactin-producing genes several centuries ago. The E.coli bacteria then began to use this toxin to eliminate its competitors and gain a dominant position in the human intestine. But this development did not occur evenly in all parts of the world.
– We have data representing genetic material from 50,000 E.coli samples gathered from four continents. When we studied these, we saw that the ability to produce the toxin is very limited and is primarily found in two particular genotypes of E.coli bacteria. Both of these circulate frequently in Norway and they are also the main genotypes of causing infections in the bloodstream in our country. In contrast, these genotypes of bacteria are rarely found in countries such as Pakistan and Bangladesh, says Corander.
The scientists involved in this study have therefore put forward a number of hypotheses on which ecological conditions drive these unwanted bacterial families away from certain population groups.
Scientists want to examine the possibilities for developing vaccines or favorable microorganisms
Corander believes that if scientists can succeed in developing vaccines against the harmful type of E.coli that produces colibactin, or a form of probiotics, this would result in notable public health benefits. Probiotics are live microorganisms which, taken in the right dosage, can be beneficial for the host health via alteration of the gut microbiome. The idea is that these measures could eliminate the unwanted colibactin-producing bacteria from the intestines.
– If we can develop a vaccine that helps the body to combat these two types of E.coli, we hope that we can substantially reduce the incidence of infections and cut down on the use of antibiotics. And not least, we can potentially reduce the risk of getting bladder, colon and rectal cancer and perhaps also some prostate cancer, he says.
The study was carried out in collaboration with scientists at the Wellcome Sanger Institute and the University of Helsinki.
Source:
Journal reference:
Mäklin, T., et al. (2024). Geographical variation in the incidence of colorectal cancer and urinary tract cancer is associated with population exposure to colibactin-producing Escherichia coli. The Lancet Microbe. doi.org/10.1016/j.lanmic.2024.101015.
