Table 1.

Clinical and preclinical studies about the association between gut microbiome and the host response to immune checkpoint inhibitors sorted by the category of bacteria

Gut microbiome categories	Mice model, or patients	Impacts	References
Bacteroidetes Bacteroides B. fragilis B. thetaiotaomicron B. caccae Bacteroides thetaiotamicron Bacteroidales	Antibiotic-treated or germ-free mice with MCA205 sarcomas receive Anti-CTLA-4(Ipilimumab) therapy	Improved response and reduced colitis	Vetizou et al. (2015) [41]
	MM patients receive Anti-CTLA-4(Ipilimumab) therapy	Reduced the risk of ICIs induced colitis	Dubin et al. (2016) [14]
	Adult MM patients receive Ipilimumab, Nivolumab Ipilimumab plus nivolumab, pembrolizumab (Anti-CTLA-4 or Anti–PD-1 or combination of Anti-CTLA-4 and Anti–PD-1 therapy)	Predicted effective therapeutic response	Frankel et al. (2017) [21]
	MM patients receive Anti-CTLA-4(Ipilimumab) therapy	Bacteroides decreased therapeutic response and decrease risk of ICIs-induced colitis	Chaput et al. (2017) [13]
	MM patients, germ-free mice with injection of BP melanoma cell receive Anti–PD-1 therapy	Bacteroidales decreased response, and attenuate systemic and antitumor immunity	Gopalakrishnan et al. (2018) [20]
Bifidobacterium B. pseudolongum B. longum	Melanoma mice with distinct commensal microbiota receive Anti–PD-L1 therapy	Delayed melanoma growth, and enhanced CD8 + T cell priming and accumulation in the tumor microenvironment	Sivan et al. (2015) [22]
	MM patients receive Anti–PD-1 therapy	Improved therapeutic response, enhanced tumor control, and improved T cell response.	Matson et al. (2018) [19]
	germ-free or specific-pathogen-free mice with injection of MC38 colorectal cancer cells receive anti CTLA-4 treatment	B. pseudolongum (belongs to B. pseudolongum) enhanced immunotherapy response through production of the metabolite inosine	Mager et al. (2020) [42]
Faecalibacterium and other Firmicutes Clostridiales Faecalibacterium Faecalibacterium prausnitzii	MM patients , germ-free mice with injection of BP melanoma cell receive Anti–PD-1 therapy	Clostridiales Faecalibacterium and Ruminococcaceae Improved response, enhanced systemic and antitumor immunity	Gopalakrishnan et al. (2018) [20]
	Adult MM patients receive Ipilimumab, Nivolumab Ipilimumab plus nivolumab, pembrolizumab (Anti-CTLA-4 or Anti–PD-1 or combination of Anti-CTLA-4 and Anti–PD-1 therapy)	Predicted effective therapeutic response	Frankel et al. (2017) [21]
	MM patients receive Anti-CTLA-4(Ipilimumab) therapy	Faecalibacterium and other Firmicutes Improved therapeutic response and higher risk of ICIs induced colitis	Chaput et al. (2017) [13]
Ruminococcaceae	MM patients, germ-free mice with injection of BP melanoma cell receive Anti–PD-1 therapy	Ruminococcaceae Improved response, and enhanced cancer immunity	Gopalakrishnan et al. (2018) [20]
Collinsella aerofaciens	MM patients receive Anti–PD-1 therapy	Improved therapeutic response, enhanced tumor control, and improved T cell response.	Matson et al. (2018)
Enterococcus faecium	MM patients receive Anti–PD-1 therapy	Improved therapeutic response, enhanced cancer immunity, and improved T cell response.	Matson et al. (2018)
Olsenella species	germ-free or specific-pathogen-free mice with injection of MC38 colorectal cancer cells receive anti CTLA-4 treatment	Improved therapeutic response, enhanced cancer immunity, and improved T cell response.	Mager et al. (2020) [42]
Lactobacillus johnsonii,	germ-free or specific-pathogen-free mice with injection of MC38 colorectal cancer cells receive anti CTLA-4 treatment	Improved therapeutic response, enhanced cancer immunity, and improved T cell response.	Mager et al. (2020) [42]
Holdemania filiformis	Adult MM patients receive Ipilimumab, Nivolumab Ipilimumab plus nivolumab, pembrolizumab (Anti-CTLA-4 or Anti–PD-1 or combination of Anti-CTLA-4 and Anti–PD-1 therapy)	Predicted effective therapeutic response	Frankel et al. (2017) [21]
Dorea formicogenerans	Adult MM patients receive Ipilimumab, Nivolumab Ipilimumab plus nivolumab, pembrolizumab (Anti-CTLA-4 or Anti–PD-1 or combination of Anti-CTLA-4 and Anti–PD-1 therapy)	Dorea formicogenerans enriched only in patients who accepted pembrolizumab and predicted effective therapeutic response	Frankel et al. (2017) [21]
Akkermansia muciniphil	NSCLC and RCC patients receive Anti-PD-L1 and Anti–PD-1	Improved therapeutic response	Routy et al. (2018) [18]
Alistipes	NSCLC and RCC patients receive Anti-PD-L1 and Anti–PD-1	Improved therapeutic response	Routy et al. (2018 )[18]

Abbreviations: CTLA-4 cytotoxic T lymphocyte–associated antigen 4, MM metastatic melanomas, NSCLC non-small-cell lung cancer, UC urothelial carcinoma, PD-1 programmed cell death protein 1, PD-L1 programmed death-ligand 1, RCC renal cell carcinoma