Gut Bacteria behind Many Colorectal Cancer Cases in Japan

Tokyo, Aug. 11 (Jiji Press)–A Japanese research team has said it found traces of genetic mutations caused by a toxin produced by certain E. coli strains in the intestines in nearly half of colorectal cancer cases in Japan. Announcing the findings Monday, the team said that the toxin called colibactin is considered to be involved in carcinogenesis, or the process by which normal cells turn into cancer cells, adding that it aims to develop a method to prevent colorectal cancer through bacterial elimination. The team includes professor Shinichi Yachida of the University of Osaka’s Graduate School of Medicine and professor Tatsuhiro Shibata of the University of Tokyo’s Institute of Medical Science. Various factors contribute to colorectal cancer, including genetics, diet and lifestyle. In addition, there have been reports that other bacteria are involved. “We want to elucidate why there are many cases of colorectal cancer involving colibactin in Japanese people and identify the infection route of E. coli strains that produce colibactin,” Yachida said. The team’s paper was published in the online edition of the U.S. journal Nature Genetics. In the study, the team analyzed 200 patients with colorectal cancer at National Cancer Center Hospital and the University of Osaka Hospital. The team found that the DNA of genes such as APC, BRAF and TP53, which contribute to the development and progression of colorectal cancer, was damaged and mutated by colibactin. The proportion in which the toxin was involved in carcinogenesis was about 45 pct. The number reached about 70 pct among younger patients who developed the disease under age 40. In gastric cancer, Helicobacter pylori is the main cause, and eradication therapy is conducted. It is not yet known whether E. coli strains that produce colibactin can be removed, but the team aims to develop a prevention method based on its findings. END [Copyright The Jiji Press, Ltd.]