Intratumoural Bacterial Co-Occurrence is Associated With an Altered Tumour Immune Microenvironment and Poor Prognosis in Colorectal Cancer.
- 1Department of Medical Biosciences, Umeå University, Umeå, Sweden.
- 2Department of Diagnostics and Intervention, Oncology, Umeå University, Umeå, Sweden.
Abstract
Alterations in the composition of the gut microbiota have been associated with colorectal cancer (CRC), with growing evidence indicating that specific microbes can have an impact on the tumour microenvironment. In this study, we investigated the associations of an oral pathobiont consortium comprising P. stomatis, F. nucleatum sensu lato and P. micra with the tumour immune microenvironment and the clinical presentation of CRC patients. Bacterial levels were quantified in fresh frozen tumour tissues using qPCR and the tumour immune environment was analysed using multiplex immunohistochemistry and multispectral imaging, profiling cytotoxic T cells, T-helper 1 cells, regulatory T cells, B cells, macrophages and regulatory immune checkpoint molecules (CTLA-4, PD-1 and PD-L1). Tumours with polymicrobial intratumoural co-occurrence were more frequently right-sided and exhibited microsatellite instability compared with tumours containing low bacterial levels or high levels of F. nucleatum sensu lato alone. Furthermore, polymicrobial tumours exhibited an altered tumour immune microenvironment, with decreased infiltration of FOXP3⁺ T regulatory cells and CD68⁺ macrophages, and increased tumour cell expression of PD-L1 in the tumour centre. Polymicrobial tumours were also associated with poorer patient survival. In conclusion, our findings suggest a link between the co-occurrence of P. stomatis, F. nucleatum sensu lato and P. micra and an altered tumour immune microenvironment in CRC. Elucidating the relationship between bacterial species and immune marker expression may enable the development of improved prognostic and predictive biomarkers, as well as new possibilities for therapeutic intervention.
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BibTeX
@article{garcia2026intratumoural,
title = {{Intratumoural Bacterial Co-Occurrence is Associated With an Altered Tumour Immune Microenvironment and Poor Prognosis in Colorectal Cancer.}},
author = {Marina Rubio Garcia and Vicky Bronnec and Maïwenn Kerdreux and William Rosenbaum and Thyra Löwenmark and Anna Löfgren-Burström and Ingrid Ljuslinder and Sofia Edin and Richard Palmqvist},
journal = {Cancer medicine},
year = {2026},
month = oct,
doi = {10.1002/cam4.72391},
url = {https://europepmc.org/article/MED/42952432},
note = {CC BY},
}
RIS
TY - JOUR
TI - Intratumoural Bacterial Co-Occurrence is Associated With an Altered Tumour Immune Microenvironment and Poor Prognosis in Colorectal Cancer.
AU - Marina Rubio Garcia
AU - Vicky Bronnec
AU - Maïwenn Kerdreux
AU - William Rosenbaum
AU - Thyra Löwenmark
AU - Anna Löfgren-Burström
AU - Ingrid Ljuslinder
AU - Sofia Edin
AU - Richard Palmqvist
PY - 2026
DA - 2026/10/29
JO - Cancer medicine
DO - 10.1002/cam4.72391
UR - https://europepmc.org/article/MED/42952432
AB - Alterations in the composition of the gut microbiota have been associated with colorectal cancer (CRC), with growing evidence indicating that specific microbes can have an impact on the tumour microenvironment. In this study, we investigated the associations of an oral pathobiont consortium comprising P. stomatis, F. nucleatum sensu lato and P. micra with the tumour immune microenvironment and the clinical presentation of CRC patients. Bacterial levels were quantified in fresh frozen tumour tissues using qPCR and the tumour immune environment was analysed using multiplex immunohistochemistry and multispectral imaging, profiling cytotoxic T cells, T-helper 1 cells, regulatory T cells, B cells, macrophages and regulatory immune checkpoint molecules (CTLA-4, PD-1 and PD-L1). Tumours with polymicrobial intratumoural co-occurrence were more frequently right-sided and exhibited microsatellite instability compared with tumours containing low bacterial levels or high levels of F. nucleatum sensu lato alone. Furthermore, polymicrobial tumours exhibited an altered tumour immune microenvironment, with decreased infiltration of FOXP3⁺ T regulatory cells and CD68⁺ macrophages, and increased tumour cell expression of PD-L1 in the tumour centre. Polymicrobial tumours were also associated with poorer patient survival. In conclusion, our findings suggest a link between the co-occurrence of P. stomatis, F. nucleatum sensu lato and P. micra and an altered tumour immune microenvironment in CRC. Elucidating the relationship between bacterial species and immune marker expression may enable the development of improved prognostic and predictive biomarkers, as well as new possibilities for therapeutic intervention.
SN - 2045-7634
ER -