Toward a Dual-Axis Model of Microbiome Modulation in Cancer Immunotherapy: Pathobiont Elimination and Functional...

Area of Science:

• Microbiome research
• Cancer immunotherapy
• Immunology

Background:

• The gut microbiome significantly influences cancer immunotherapy effectiveness, including responses to immune checkpoint inhibitors (ICIs) and CAR-T cell therapy.
• Microbiome-targeted interventions like fecal microbiome transplantation (FMT) and live biotherapeutic products (LBPs) show promise in enhancing antitumor immunity.
• However, patient responses to these therapies are inconsistent and not solely explained by the presence of donor microbes.

Purpose of the Study:

• To propose a model hypothesis integrating interventional, observational, and microbial ecology data to explain how microbiome-targeted therapies impact immunotherapy response.
• To guide future clinical trial design, analysis, and interpretation in microbiome-based cancer immunotherapy.

Main Methods:

• Integration of evidence from clinical interventional trials and observational cohort studies.
• Application of principles from gut microbial ecology to develop a mechanistic model.
• Hypothesis generation based on existing data regarding microbiome-host-therapy interactions.

Main Results:

• A proposed dual-axis model for microbiome-targeted immunotherapy enhancement: (1) elimination of immunosuppressive pathobionts and (2) functional restoration of the gut ecosystem.
• Therapeutic success depends on ecological processes like colonization resistance and microbial community resilience, influencing the ability of administered microbes to displace dysbiotic communities.
• Complete donor engraftment is neither necessary nor sufficient for clinical benefit, suggesting a focus on functional microbial restoration.

Conclusions:

• A dual-mechanism model involving pathobiont elimination and functional microbial restoration explains microbiome-mediated improvements in cancer immunotherapy.
• A balanced, immune-permissive gut ecosystem is crucial for successful microbiome-targeted cancer therapy.
• This ecological perspective helps reconcile discrepancies across different study designs and intervention types.