Peptostreptococcus anaerobius promotes colorectal carcinogenesis and modulates tumour immunity


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 α21 integrin, a receptor frequently overexpressed in human CRC tumours and cell lines. Interaction between PCWBR2 and integrin α21 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 α21 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 α21-PI3K–Akt–NF-κB signalling axis and identify the PCWBR2-integrin α21 axis as a potential therapeutic target for CRC.

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Fig. 1: P. anaerobius promotes colonic tumorigenesis in ApcMin/+ mice.
Fig. 2: P. anaerobius attaches to colon cells through its surface protein PCWBR2.
Fig. 3: P. anaerobius attaches to colon cells by interacting with the epithelial cell surface receptor integrin α21.
Fig. 4: P. anaerobius mediates integrin β12 signalling to activate the PI3K–Akt pathway to promote cell proliferation in vitro, and these effects are verified in ApcMin/+ mouse model.
Fig. 5: P. anaerobius modifies the tumour immune microenvironment to promote CRC.
Fig. 6: Blockade of integrin β12-attenuated P. anaerobius-associated colon tumorigenesis in ApcMin/+ mice.

Data availability

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.

Author information




X.L. performed the cell line and mice experiments and drafted the manuscript. L.T., E.S.H.C., C.H.S. and M.Y.Y.G. performed the mice experiments. C.C.W. revised the manuscript. O.O.C. analysed the RNA-seq data. A.W.H.C. analysed the H&E staining data. F.K.L.C. and J.J.Y.S. commented on the study. J.Y. designed and supervised the study and revised the manuscript.

Corresponding author

Correspondence to Jun Yu.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–14, Supplementary Tables 1 and 2, Supplementary Table 3.3, Supplementary Tables 4–6, Supplementary Video legend, uncropped gels and blots.

Reporting Summary

Supplementary Table 3.1 and 3.2

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.

Supplementary Video 1

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).

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