Emerging evidence implicates a role of the gut microbiota in colorectal cancer (CRC). Peptostreptococcus anaerobius (P. anaerobius) is an anaerobic bacterium selectively enriched in the faecal and mucosal microbiota from patients with CRC, but its causative role and molecular mechanism in promoting tumorigenesis remain unestablished. We demonstrate that P. anaerobius adheres to the CRC mucosa and accelerates CRC development in ApcMin/+ mice. In vitro assays and transmission electron microscopy revealed that P. anaerobius selectively adheres to CRC cell lines (HT-29 and Caco-2) compared to normal colonic epithelial cells (NCM460). We identified a P. anaerobius surface protein, putative cell wall binding repeat 2 (PCWBR2), which directly interacts with colonic cell lines via α2/β1 integrin, a receptor frequently overexpressed in human CRC tumours and cell lines. Interaction between PCWBR2 and integrin α2/β1 induces the activation of the PI3K–Akt pathway in CRC cells via phospho-focal adhesion kinase, leading to increased cell proliferation and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. NF-κB in turn triggers a pro-inflammatory response as indicated by increased levels of cytokines, such as interleukin-10 and interferon-γ in the tumours of P. anaerobius-treated ApcMin/+ mice. Analyses of tumour-infiltrating immune cell populations in P. anaerobius-treated ApcMin/+ mice revealed significant expansion of myeloid-derived suppressor cells, tumour-associated macrophages and granulocytic tumour-associated neutrophils, which are associated with chronic inflammation and tumour progression. Blockade of integrin α2/β1 by RGDS peptide, small interfering RNA or antibodies all impair P. anaerobius attachment and abolish P. anaerobius-mediated oncogenic response in vitro and in vivo. Collectively, we show that P. anaerobius drives CRC via a PCWBR2-integrin α2/β1-PI3K–Akt–NF-κB signalling axis and identify the PCWBR2-integrin α2/β1 axis as a potential therapeutic target for CRC.
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All datasets and raw data generated and/or analysed during the current study are available from the corresponding author upon reasonable request. The RNA-seq data are deposited with the NCBI with accession code PRJNA544569.
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This project was supported by the Science and Technology Program Grant Shenzhen (no. JCYJ20170413161534162), HMRF Hong Kong (no. 17160862), a grant from the Faculty of Medicine CUHK on Microbiota Research, RGC-GRF Hong Kong (nos. 14111216 and 14163817), a Vice-Chancellor’s Discretionary Fund CUHK (no. 4930711), and the Shenzhen Virtual University Park Support Scheme to the CUHK Shenzhen Research Institute.
The authors declare no competing interests.
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Supplementary Figs. 1–14, Supplementary Tables 1 and 2, Supplementary Table 3.3, Supplementary Tables 4–6, Supplementary Video legend, uncropped gels and blots.
3.1, Gene expression levels detected by RNA-sequencing in HT-29 cell line after P. anaerobius treatment. 3.2, Gene expression levels detected by RNA-sequencing in Caco-2 cell line after P. anaerobius treatment.
Fluorescent live cell microscopy showing that FITC-labelled P. anaerobius attaches to Caco-2 cells. P. anaerobius was labelled with AF488 DIBO and immediately co-cultured with Caco-2 cells.
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Long, X., Wong, C.C., Tong, L. et al. Peptostreptococcus anaerobius promotes colorectal carcinogenesis and modulates tumour immunity. Nat Microbiol 4, 2319–2330 (2019). https://doi.org/10.1038/s41564-019-0541-3
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