Table 1.
Major gut microbial taxa and their predominant influence on systemic immunity and response to immunotherapy
| Gut Taxa | Immune effect/Treatment response | Study type | Cancer type | Reference |
|---|---|---|---|---|
| Predominately positive influence | ||||
| Firmicutes | ||||
| Faecalibacterium prauznitzii | Boosts effector T-cells and dampens T-regs [38]. | Humans | Melanoma | Gopalakrishnan et al. (2018) |
| Faecalibacterium spp. | Increases efficacy of anti-CTLA-4 immunotherapy [44]. | Humans | Multiple myeloma | Chaput et al. (2017) |
| Eubacterium limosum Clostridiales spp. Ruminococcaceae spp. Phasolarctobacterium spp. |
Boost CD8+ T-cells and enhance anti-PD-1 responses [33]. | Cell line | Colorectal Adenocarcinoma Cell line (MC38) |
Tanoue et al. (2019) |
| Fusobacteria | ||||
| Fusobacterium ulcerans Fusobacterium varium |
Boost CD8+ T-cells and enhance anti-PD-1 responses [33]. | Cell line | MC38 | Tanoue et al. (2019) |
| Verrucomicrobia | ||||
| Akkermansia muciniphilia | Increase in memory T-cells and decrease in T-regs in the TME [39]. | Humans | Epithelial tumors | Routy et al. (2018) |
| Increases mucus layer of the gut to prevent lipopolysaccharides absorption [39, 41]. | Humans; review | Epithelial tumors | Routy et al. (2018); Routy et al. (2018) | |
| Mixed influence | ||||
| Bacteroidetes | ||||
| Bacteroides fragilis | Increases efficacy of anti-CTLA-4 immunotherapy [42]. | Human/Animal/Cell line | Epithelial tumors | Vetizou et al. (2015) |
| Promotion of T-regs through polysaccharide-A [40]. | Humans | N/A | Telesford et al. (2015) | |
| Higher IL-12 levels in transplant recipients [47]. | Animal/Cell line | Cervical cancer | Uribe-Herranz et al. (2018) | |
| Bacteroides thetaiotaomicron | Increases efficacy of anti-CTLA-4 and anti-PD-1 immunotherapy [Vetizou et al. showed in anti-CTLA–4 alone; Frankel et al. showed in dual setting] [42, 45]. | Humans | Melanoma | Frankel et al. (2017) |
| Bacteroides spp. | Inferior response of anti-CTLA-4 immunotherapy [44]. | Humans | Multiple myeloma | Chaput et al. (2017) |
| Actinobacteria | ||||
| Bifidobacterium longum | Increases CD8+ T-cells [43, 46]. | Animal/Cell line | Melanoma | Sivan et al. (2015) |
| Humans | Melanoma | Matson et al. (2018) | ||
| Bifidobacterium bifidum | Induces naïve T-cell differentiation into T-regs and increases IL-10. Increases the integrity of epithelial barrier [41]. |
Review | N/A | Routy et al. (2018) |
| Predominately negative influence | ||||
| Proteobacteria | ||||
| Enterobacteriaceae | Inferior response and survival [41]. | Review | N/A | Routy et al. (2018) |