# Microbiome-tumour interactions

Source: https://onco.cc/pathways/microbiome-tumour/  
OnCo record `microbiome-tumour` (Pathway). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The bacteria in the gut, and even inside tumours, influence whether cancer starts and whether immunotherapy works. Transplanting stool from responders has made some non-responders respond.

## Summary

Gut microbiota modulate systemic immunity (Bifidobacterium, Akkermansia, Faecalibacterium associated with PD-1 response; antibiotics associated with worse outcomes); faecal microbiota transplant from responders converted a fraction of refractory melanoma patients to responders (2021, and 2023-25 follow-ups). Intratumoural bacteria (Fusobacterium nucleatum in colorectal cancer, Gammaproteobacteria degrading gemcitabine in pancreatic cancer) affect chemoresistance and inflammation; colibactin-producing pks+ E. coli leaves a mutational signature in CRC. 'Polymorphic microbiomes' is a 2022 hallmark. Defined consortia (VE800, SER-155) and diet interventions are in trials; causality beyond melanoma is not settled.

## Fields

- Kind: Pathway
- Last checked: 2026-09-08
- Tags: mechanism
- Analogy: Soil bacteria decide whether a garden thrives. Some feed the plants' defenders, some produce poisons, and some even eat the pesticide before it reaches the weeds.
- Interventions: FMT from responders with PD-1 blockade (phase 2); Defined bacterial consortia (VE800, SER-155) and diet (fibre) trials; Antibiotic stewardship around immunotherapy; Fusobacterium-targeted strategies (research)

## Notes

- Leading programmes: Wargo (MD Anderson); Zitvogel (Gustave Roussy); Gajewski (Chicago); Sears (Johns Hopkins) on colibactin; Straussman (Weizmann) on intratumoural bacteria.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Microbiome
- Davar et al., Fecal microbiota transplant overcomes resistance to anti-PD-1 therapy in melanoma (Science 2021): https://doi.org/10.1126/science.abf3363
- Hanahan, Hallmarks of Cancer: New Dimensions (Cancer Discovery 2022): https://doi.org/10.1158/2159-8290.CD-21-1059

## Connected records

- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma)](https://onco.cc/cancers/malt-lymphoma/), [Marginal zone lymphoma](https://onco.cc/cancers/marginal-zone-lymphoma/), [Melanoma](https://onco.cc/cancers/melanoma/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/)
- targets: [BCL10](https://onco.cc/targets/bcl10/), [BIRC3](https://onco.cc/targets/birc3/), [MALT1](https://onco.cc/targets/malt1/), [PD-1](https://onco.cc/targets/pd1/), [TNFAIP3](https://onco.cc/targets/tnfaip3/)
- institutions: [Abramson Cancer Center, University of Pennsylvania](https://onco.cc/institutions/penn-abramson/), [Gustave Roussy](https://onco.cc/institutions/gustave-roussy/), [Johns Hopkins Hospital / Sidney Kimmel Comprehensive Cancer Center](https://onco.cc/institutions/johns-hopkins/), [MD Anderson Cancer Center](https://onco.cc/institutions/md-anderson/)
- pathways: [Inflammation & NF-κB](https://onco.cc/pathways/inflammation-nfkb/), [PD-1 / PD-L1 immune checkpoint & T-cell activation](https://onco.cc/pathways/pd1-checkpoint/), [Tumour microenvironment (TME)](https://onco.cc/pathways/tumor-microenvironment/)
- terms: [Enabling characteristic: tumour-promoting inflammation](https://onco.cc/terms/tumor-promoting-inflammation/), [Gut microbiome diversity and composition](https://onco.cc/terms/gut-microbiome-diversity/), [Hallmark (2022): polymorphic microbiomes](https://onco.cc/terms/polymorphic-microbiomes/), [Mutational signature](https://onco.cc/terms/mutational-signature/)
- key papers: [Fecal microbiota transplant overcomes resistance to anti-PD-1 therapy in melanoma patients](https://onco.cc/key-papers/paper-davar-science/), [Geographic and age variations in mutational processes in colorectal cancer](https://onco.cc/key-papers/paper-diaz-gay-colibactin-geographic-age-mutational-processes-nature-2025/), [Hallmarks of Cancer 2022: adding phenotypic plasticity, epigenetic reprogramming, microbiomes and senescent cells](https://onco.cc/key-papers/paper-hallmarks-new-dimensions-cancer-discov-2022/)
- roadmaps: [Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation](https://onco.cc/roadmaps/colorectal-roadmap/)
- ideas: [Find out what is driving early-onset bowel cancer, starting with colibactin, before extending screening any further](https://onco.cc/ideas/idea-crc-early-onset-cause-hunt/), [Microbiome transplant as a routine immunotherapy adjunct](https://onco.cc/ideas/idea-microbiome-io-fmt/)
- technologies: [Dietary fibre and the gut microbiome for immunotherapy response](https://onco.cc/technologies/dietary-fibre-microbiome-io/), [Faecal microbiota transplantation for PD-1 non-responders](https://onco.cc/technologies/fmt-checkpoint-nonresponders/), [Probiotics, antibiotics and stewardship around immunotherapy](https://onco.cc/technologies/probiotics-antibiotic-stewardship-io/)
- trials: [FMT plus pembrolizumab in anti-PD-1-refractory melanoma (Pittsburgh)](https://onco.cc/trials/fmt-pd1-refractory-melanoma-pitt/), [MIMic-01: healthy-donor FMT plus anti-PD-1, first-line melanoma](https://onco.cc/trials/mimic-01/)

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