It is not only tobacco use and frequent contact with toxic solvents that lead to an increased risk of bladder cancer. Repeated or long-lasting urinary tract infections could also increase the likelihood of such a disease, as French researchers report in the journal PLoS Pathogens.
The vast majority of urinary tract infections are caused by so-called uropathogenic E. coli bacteria (UPEC). Many of them release the toxin colibactin. The scientists found evidence of colibactin production by analyzing urine samples in nearly one in four patients. In animal experiments, they were able to demonstrate that this toxin can damage the DNA of cells in the bladder wall and thus trigger the development of cancer growth. The pathogens of urinary tract infections enter the lower urinary tract from the intestine. Preventive treatment that eliminates the pathogen reservoir of UPEC bacteria in the intestine would therefore be helpful.
“Our results show that patients suffering from urinary tract infections should be systematically examined for evidence of colibactin production,” say Jean-Philippe Nougayréde and Eric Oswald of the Université de Toulouse. Women are most likely to contract urinary tract infections. More than 60 percent are affected at least once in a lifetime. The infection can be symptomless, limited to the lower urinary tract or even detected in the kidneys. If the pathogens enter the bloodstream, a life-threatening urosepsis can develop.
Researchers collected urine samples from 223 patients suffering from E. coli infection of the upper or lower urinary tract. By detecting a by-product produced in colibactin production, they identified a release of the toxin by UPEC bacteria in 55 patients. Experiments with mice revealed that urinary tract infections with these pathogens damaged the DNA of cells in the bladder wall to such an extent that mutations could develop that promote cancer growth.
The researchers conclude that persistent urinary tract infections, including symptomless ones, by colibactin-forming UPEC bacteria can damage the cells of the urinary tract in the same way in humans, increasing the likelihood of cancer. Previous research has shown that the detection of such pathogens in the intestine is associated with an increased risk of colorectal cancer. Their targeted elimination in the intestine would reduce the risk of developing bowel and bladder cancer. However, this link would first have to be confirmed by further investigations.