This narrative review argues that both gut microbiota and intratumoral microbiota can shape immune checkpoint inhibition (ICI) outcomes via immune modulation (e.g., SCFAs/tryptophan metabolites affecting Tregs/CTLs) and via local/ systemic effects on the tumor microenvironment (TME), including the possibility that bacteria colonize tumors but also that much of the field remains limited by causality, contamination risk, and model/host heterogeneity .
Core strengths are breadth and mechanistic mapping; core weaknesses are that it is narrative, leans heavily on associative/corroborative evidence, and the translational βactionabilityβ is constrained by reproducibility and context-dependency .
The paper draws from both clinical and mechanistic preclinical literature. The next plot visualizes (from the paperβs extracted trial examples in your provided research-data) how often βphase 1 FMT + anti-PD-1β appears with responder counts.
The reviewβs causal direction (microbiota β therapy efficacy) is consistent with mouse work showing microbiota are required for optimal responses and implicating mechanisms such as TLR4-dependent TNF/ROS dynamics for CpG-ODN/anti-IL-10R and platinum-based chemotherapy responses .
Skeptical caveat: antibiotic cocktails and germ-free housing can affect physiology beyond microbiota depletion; thus causality in mice should not be assumed to map directly to human interventions without careful controls .
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