[ITmedia News] Approximately half of Japanese colon cancer cases involve “toxins from intestinal bacteria” 70% of cases occur in people under 40 years of age University of Tokyo and Osaka University conduct whole genome analysis of 200 people

The paper ``Prevalence and chronology of colibactin-associated mutational processes and their microbiome spectra in Japanese colorectal cancer'' published in the scientific journal ``Nature Genetics'' by researchers affiliated with the Institute of Medical Science, the University of Tokyo, Osaka University, the National Cancer Center, and the Tokyo University of Science is a research report that found that specific intestinal bacteria are involved in the development of colorectal cancer in Japanese people.

The research team conducted genetic analysis (whole genome analysis) on 200 Japanese patients with colorectal cancer and found that in approximately half of the cases (44.8% of non-highly mutated cases), a special type of Escherichia coli that produces a toxin called colibactin was involved in the onset of the disease. Previous research shows that the rate is around 5-20% in other countries, including Europe and America, so it can be seen that there are many Japanese cases.

In particular, in young people with colorectal cancer who develop between the ages of 21 and 40, 70% (seven out of 10) of them had evidence of damage to their cell DNA (mutation signature) caused by the bacterial toxin.

Damage caused by toxins affects important genes involved in cancer development (driver genes such as APC, BRAF, and TP53). In one case, it was shown that the first genetic abnormality that triggers APC carcinogenesis may occur already in childhood, when the patient is less than 10 years old. This suggests that certain bacteria that have been present in the stomach since childhood may continue to damage DNA little by little over decades, eventually causing colon cancer.

Additionally, this gene mutation caused by colibactin is more common in the generation born after 1965, and may be related to the increased incidence of colorectal cancer in younger generations.

Furthermore, AI analysis of intestinal bacteria revealed that colorectal cancer can be divided into four groups. It has also been suggested that the type of carcinogenesis caused by colibactin follows a different route from that caused by bacteria such as Fusobacterium, which has attracted attention up to now.

Source and Image Credits: Shiba, S., Yachida, S., Mizutani, S. et al. Prevalence and chronology of colibactin-associated mutational processes and their microbiome spectra in Japanese colorectal cancer. Nat Genet 58, 2211–2225 (2026). https://doi.org/10.1038/s41588-026-02692-x

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