Table 1.

Studies on gut microbiota target innate and adaptive immune cells to promote ICI efficacy

Year	Cancer types	ICI	Beneficial gut microbiota	Interventions factors and/or biological effects	References
2015	Melanoma	PD-L1 inhibitor	Bifidobacterium	DCs and CD8 + T cells	[16]
2015	Melanoma	CTLA4 inhibitor	Bacteroides fragilis	Tumor draining lymph nodes: Th1; TME: DCs	[17]
2018	NSCLC, RCC, Urothelial carcinoma	PD-1 inhibitor, CTLA4 inhibitor	Akkermansia muciniphila	TME: IL-12 and CCR9 + CXCR3 + CD4 + T lymphocytes	[31]
2018	Melanoma	PD-1 inhibitor	Faecalibacterium, Ruminococcaceae, Clostridiales	Mice receiving R-FMT: Increased innate effector cells and decreased suppressive myeloid cells; Mice receiving NR-FMT: Increased RORγT+ T helper 17 cells	[32]
2018	Melanoma	PD-L1 inhibitor	Bifidobacterium longum, Collinsella aerofaciens, Enterococcus faecium	Mice receiving R-FMT: Augmented T cell responses	[33]
2017	Melanoma	CTLA4 inhibitor	Faecalibacterium	CD4 + T cells and CD25	[49]
2019	Adenocarcinoma, melanoma	PD-1 inhibitor	Eleven strains	IFNγ + CD8 T cell, CD103 + DC, and MHC Ia	[50]
2020	CRC, Intestinal cancer, Bladder cancer, melanoma	PD-L1 inhibitor, CTLA4 inhibitor	Bifidobacterium pseudolongum, Akkermansia muciniphila, Lactobacillus johnsonii, Olsenella species	DCs and Th1; Inosine: A2AR on Th1	[51]
2020	Colon cancer, T cell lymphoma	CD47 inhibitor	Bifidobacterium	STING signaling and DCs	[52]
2021	Melanoma	PD-1 inhibitor	Enterococcaceae, Enterococcus, Streptococcus australis	FMT-R patients: TME: CD8 + T cell; Gut: APC	[15]
2021	Melanoma	PD-1 inhibitor	Lachnospiraceae, Ruminococcaceae families, Bifidobacteriaceae, Coriobacteriaceae families	FMT-R patients: PBMCs: CD8 + T cells and MAIT cells; TME: CD8 + T cells, HLA II, CD74 and GZMK FMT-NR patients: Increased myeloid cells and CD4 + regulatory T cells	[14]
2021	Lymphoma, Colon carcinoma, Melanoma, Breast carcinoma	ICI	A high-fiber diet, Akkermansia muciniphila	Monocytes, Macrophages, NK cells, DCs, Type I IFN, and STING	[53]

APC: antigen presenting cell; A_2AR: adenosine 2A receptor; CRC: colorectal cancer; CTLA4: cytotoxic T lymphocyte-associated antigen 4; DC: dendritic cell; FMT: fecal microbiota transplant; FMT-R: responders to fecal microbiota transplant treatment; FMT-NR: non-responders to fecal microbiota transplant treatment; GZMK: granzyme K; ICI: immune checkpoint inhibitor; IFN: interferon; MAIT: mucosal-associated invariant T; MHC: major histocompatibility; NK: natural killer; NSCLC: non-small cell lung cancer; NR-FMT: fecal microbiota transplants from non-responders to immune checkpoint inhibitor; PBMCs: peripheral blood mononuclear cells; PD-1: programmed cell death 1; PD-L1: programmed cell death ligand 1; RCC: renal cell carcinoma; R-FMT: fecal microbiota transplants from responders to immune checkpoint inhibitor; STING: stimulator of interferon gene; Th1: T helper 1; and TME: tumor microenvironment