Oral Bacterial Peugeot Bacteria Deteriorates Colorectal Cancer Prognosis
Jul 24, 2025
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A joint research team led by Kim Han-sang, a professor of oncology at Yonsei Cancer Hospital, Han Yoon-dae, a professor of colorectal surgery, Lee In-seok, a professor of life systems, Choi Il-seok, Dr. Kim Kyung-ah, and Dr. Kim Sang-chul of the National Institute of Health announced on the 24th that they have identified the mechanism by which oral bacteria found in colorectal cancer disrupt the immune environment in cancer tissues and worsen the prognosis.
The results of this study were published in the latest issue of the international academic journal 'Gut Microbes (IF 11)'.
Peugeot bacteria are commonly present in the oral cavity and are a major causative agent of periodontitis. However, the bacteria, which do not normally live in the large intestine, are unusually detected in colon tissue cancer cells in about half of colorectal cancer. Recently, in addition to colorectal cancer, reports have also been published that Peugeot bacteria have been detected in other cancer tissues such as breast cancer, pancreatic cancer, and stomach cancer.
The research team confirmed through prior research that the treatment prognosis of patients infected with Peugeot bacteria in colon cancer is not good compared to patients who are not infected. In this study, patients infected with Peugeot bacteria showed decreased immunity of T cells and increased immunity of regulatory T cells, resulting in decreased anti-tumor immune function. This confirmed that Peugeot bacteria are associated with poor prognosis of colon cancer, but its mechanism has not yet been clarified.
The research team conducted single-cell RNA sequencing analysis in tissues of a total of 42 colorectal cancer patients, including 19 positive and negative Peugeot bacteria, to investigate the effect of Peugeot bacteria on tumor microenvironment. Single-cell RNA sequencing assays allow us to observe single-cell level gene expression in tissues and analyze interactions between cells, thus providing more accurate information about phenomena occurring within tissues.
As a result of the analysis, it was confirmed that the differentiation status of immune cells in Peugeot bacteria-positive patients was different from that of negative patients. In positive patients, Peugeot bacteria have been shown to interfere with interactions with tumor-associated macrophages, thereby inhibiting the development of immunoglobulin A (IgA) plasma cells and the production of secretory IgA (sIgA). The higher the maturity of IgA, the better the prognosis of cancer, whereas the lower the maturity of IgA in Peugeot bacteria-positive colorectal cancer, the worse the prognosis.
Additionally, the team re-verified that Peugeot bacteria are directly responsible for the inhibition of sIgA production through aseptic mouse experiments.
Single-cell RNA sequencing analysis in colorectal tissues of the germfree mouse model and the Peugeot bacteria infection model showed that IgA maturation was inhibited in the Peugeot bacteria-positive model. It was confirmed that the interaction between IgA plasma cells and 'M2 macrophages', responsible for innate immunity, was reduced, resulting in a weakened sIgA function. As a result, it has been shown that the inability to effectively block bacterial penetration increases the bacterial burden in tumors and causes chronic inflammation, worsening the prognosis.
Professor Kim Han-sang "This study identified the mechanism by which oral bacteria Peugeot bacteria deteriorate the treatment prognosis of colorectal cancer."We expect that this mechanism can be used to apply customized treatment strategies to patients with Peugeot bacteria-positive colorectal cancer. " Professor Lee In-seok said, `This study is significant as it is the first to investigate the effect of Peugeot bacteria on B cell maturation in colon tissues using single-cell genomic bioinformation analysis technology.'
Meanwhile, this study was conducted with the support of the Korea Centers for Disease Control and Prevention's postgenomic multivitro genomics project, the Korea Research Foundation's microbial control and application source technology development project, the Ministry of Science and ICT's oral microbiome function evaluation platform and disease control source technology, and the Korea Health Industry Promotion Agency's global joint research project.
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This article was translated by Naver AI translator.
