Table 1.

Microbiota involved in cancer progression

System	Cancer type	Microbiota	Tumor promotion /Tumor suppression	Tumor Behavior	Molecular Mechanism	Ref.
Digestive System	Colorectal Cancer	Fusobacterium nucleatum	Tumor promotion	Proliferation and invasion	F. nucleatum regulates E-cadherin/β-catenin signaling pathway to promote colorectal proliferation and invasion.	[52]
			Tumor promotion	Proliferation	F. nucleatum activates TLR4 and upregulates miR-21 to promote colorectal cancer proliferation.	[55]
		Enterotoxigenic Bacteroides fragilis (ETBF)	Tumor promotion	Tumorigenesis	ETBF selectively activates STAT3 and induces TH17 inflammatory infiltrates for enhancing tumor growth.	[57]
		Peptostreptococcus anaerobius	Tumor promotion	Proliferation and dysplasia	P. anaerobius interacts with TLR2 and TLR4 to increase intracellular ROS level, thus increases colon proliferation and dysplasia.	[59]
			Tumor promotion	Initiation and proliferation	P. anaerobius drives CRC tumorigenesis via PCWBR2/ PI3K/AKT/NF-κB signaling axis.	[60]
		Campylobacter jejuni	Tumor promotion	Initiation and proliferation	C. jejuni induces DNA damage and promotes colorectal tumorigenesis and growth via cytolethal distending toxin.	[51]
		Streptococcus gallolyticus	Tumor promotion	Initiation	S. gallolyticus promotes normal or premalignant colorectal tissues into malignant tumor via IL-1, COX-2, and IL-8 induction.	[61]
		Clostridium butyricum	Tumor suppression	Proliferation and metastasis	C. butyricum inhibits intestinal tumor development by modulating Wnt signaling and gut microbiota.	[62]
		Bacteroides fragilis	Tumor suppression	Cancer development	B. fragilis prevents colitis-associated CRC by inhibiting the expression of CCR5.	[63]
		Streptococcus thermophilus	Tumor suppression	Tumorigenesis	S. thermophilus secretes β-Galactosidase to inhibit tumorigenesis.	[64]
	Gastric Cancer	Helicobacter pylori	Tumor promotion	Invasion	H. pylori infection increase VCAM1 expression in CAFs via JAK/STAT1 signaling pathway to facilitate tumor invasion.	[53]
	Esophageal Carcinoma	Porphyromonas gingivalis	Tumor promotion	Proliferation and migration	P. gingivalis promote ESCC proliferation and migration via the miR-194/GRHL3/PTEN/ AKT signaling axis	[43]
	Pancreatic Cancer	Porphyromonas gingivalis	Tumor promotion	Proliferation	P. gingivalis enhances tumor cell proliferation through strengthening AKT signaling and Cyclin D1 expression.	[49]
	Liver Cancer	Helicobacter hepaticus	Tumor promotion	Proliferation	H. hepaticus promotes HCC by activating NF-κB regulated networks associated with innate and Th1-type adaptive immunity.	[65]
	Oral Cancer	Porphyromonas gingivalis	Tumor suppression	Proliferation	P. gingivalis inhibits proliferation of oral cancer cells by inducing G1 cell cycle arrest.	[35]
			Tumor promotion	Proliferation	P. gingivalis actives the miR-21/PDCD4/AP-1 signaling pathway to promote the proliferation of oral cancer.	[66]
Non-Digestive System	Lung Cancer	Herbaspirillum	Tumor promotion	Proliferation	Herbaspirillum stimulates IL-1β and IL-23 production, induces activation of Vγ6+Vδ1+ γδ T cells and tumor cell proliferation.	[67]
		Veillonella	Tumor promotion	Cancer development	Veillonella activates PI3K signaling pathway to participate in tumor development.	[68]
	Breast Cancer	Enterotoxigenic Bacteroides fragilis (ETBF)	Tumor promotion	Proliferation and migration	ETBF triggers breast cancer growth and metastasis through β-catenin and Notch1 pathways.	[69]
		Faecalibacterium prausnitzii	Tumor suppression	Proliferation	F. prausnitzii suppresses the growth of breast cancer cells through inhibition of IL-6/STAT3 pathway.	[70]

FadA Fusobacterium adhesin A, STAT3 Signal transducer and activator of transcription3, TLR2 toll-like receptor2, TLR4 toll-like receptor4, ROS reactive oxygen species, PCWBR2 putative cell wall binding repeat 2, SGMB Streptococcus gallolyticus member bacteria, IL-1 interleukin 1, COX-2 cyclooxygenase-2, IL-8 interleukin 8, CCR5 CC chemokine receptor 5, VCAM1 Vascular cell adhesion molecular 1, CAF cancer-associated fibroblasts, ESCC esophageal squamous cell carcinoma, IL-1β interleukin 1β, IL-23 interleukin 23, PI3K phosphatidylinositol-3 kinase, HCC hepatocellular carcinoma, PDCD4 programmed cell death 4, AP-1 activating protein-1