Table 1.

Evidence of the impact of skin and gut microbiome in cancer and response to treatment, and associated biomarkers. PFS: progression-free survival, OS: overall survival.

Microbiome	Reference	Bacteria	Results	Biomarker
Skin	Mizuhashi, S., et al. [16]	Corynebacterium	Advanced stages (III/IV) acral melanoma	IL-17A
	Naik, S., et al. [17]	Staphylococcous epidermidis	Normalizes IL-17A production, related with tumor growth and anti-tumor immunity	IL-17A
	Nakatsuji, T., et al. [18]	Staphylococcous epidermidis	Reduces the incidence of UV-induced skin tumors	6-HAP (6-N-hydroxyaminopurine)
Gut	Sivan, A., et al. [19]	Bifidobacterium	Enhances anti-tumor response of anti PD-1	CD8+ T cells
	Bessell, C.A., et al. [20]	Bifidobacterium	Enhances anti-tumor immunity by amplifying T cells	CD8+ T cell epitope SVY
	Vétizou, M., et al. [21]	Bacteroides fragilis, B. thetaiotaomicron and, Burkholderia	Associated with response to anti-CTLA4	IL-12 induced T cell response
	Miller, P.L., Carson, T.L. [22]	Bacteroides fragilis, Burkholderia cepacia and Faecalibacterium	Associated with response to anti-CTLA4	IL-12 induced T cell response
	Frankel, A.E., et al. [23]	Bacteroides caccae, Streptococcus parasanguinis, Faecalibacterium prausnitzii, Holdemania filiformis, Bacteroides thetaiotamicron and Dorea formicigenerans	Associated with response to immune checkpoint blockade	Anacardic acid and other metabolites
	Wind, T.T., et al. [24]	Streptococcus parasanguinis and Bacteroides massiliensis	Associated with PFS and OS, respectively, in response to immune checkpoint blockade	Aspartate, thiamine diphosphate, NAD/NADH, glycolysis, TCA and glyoxylate, and pyruvate pathways
		Peptostreptococcaceae	Shorter PFS and OS	Peptidoglycan and methanogenesis pathways
	Chaput, N., et al. [25]	Faecalibacterium and Firmicutes	Longer OS, PFS and immune-induced colitis when treated with anti-CTLA4	CD4+ T cells and higher increase in serum CD25 cells
	Tanoue, T., et al. [26]	Bacteroides, Ruminococcaceae, Fusobacterium, Phascolarctobacterium, Eubacterium, Paraprevotella, Alistipes	Enhanced efficacy of ICI	Interferon-γ-producing CD8 T cells
	Mager, L.F., et al. [27]	Bifidobacterium pseudolongum, Lactobacillus johnsonii, and Olsenella	Enhanced efficacy of ICI	Increased inosine and anti-tumor T cells
	Matson, V., et al. [28]	Bifidobacterium longum, Collinsella aerofaciens, and Enterococcus faecium	Enhanced efficacy of ICI	SIY–specific CD8+ T cells
	Gopalakrishnan, V., et al. [29]	Ruminococcaceae and Clostridiales	Responders to anti-PD-1	CD45+ and CD8+ immune T cells
		Bacteroidales	Non responders to anti-PD-1	RORγT+ Th17, CD4+ FoxP3+ T cells, CD4+ IL-17+
	McCulloch, J.A., et al. [30]	Actinobacteria, Lachnospiraceae, Ruminococcaceae	Responders to anti-PD-1	Protective membrane mucins (MUC13 and MUC20) and apolipoproteins (APOA1, APOA4 and APOB)
		Bacteroidetes and Proteobacteria	Non responders to anti-PD-1	High neutrophil–lymphocyte ratio and proinflammatory cytoquines (ILB, CXCL8, SOD2)
	Limeta, A., et al. [31]	Faecalibacterium and Barnesiella intestinihominis	Responders to anti-PD-1	Upregulation of inositol metabolism and vitamin B pathway
		Bacteroides	Non responders to anti-PD-1	Upregulation of biosynthesis pathways