Table 3.

Immunosuppressive effects of MSCs on several immune cell types which contribute to tumor progression

Immune cells	MSCs effects	References
Neutrophils	Induction of CD11b/Ly6G-positive neutrophils to massive T-cell inhibition in vitro, and enhancement of breast carcinoma tumor growth in vivo IL-6 from cancer-derived MSCs promotes neutrophil activation via STAT3-ERK1/2 signaling and induces their polarization towards a tumor-supportive phenotype in gastric cancer	[60, 61]
Dendritic cells	Suppression of dendritic cell differentiation by downregulating IFN-γ and TNF-α expression Regulation of maturation of dendritic cells via PGE2 signalling Promotion of immunosuppressive effects on dendritic cells and tumor growth in murine melanoma tumor models	[62–64]
Natural killer	Block its activity, suppressed its proliferation and cytokine secretion and reduce its ability to produce IFN-γ	[65, 66]
T-cells	Repress T-cells proliferation and increase apoptosis by secreting soluble TGF-β Secrete IDO, which inhibits T-cells through tryptophan depletion	[13, 67–70]
B-cells	Repress B-cell proliferation by secreting soluble factors Reduce antibody production and inhibit their differentiation to plasma cells Attenuate B-cell proliferation and antibody production by INF-y stimulated-MSCs overexpression galectin-9	[70–73]
Macrophages	Induce macrophages to produce the anti-inflammatory factor IL-10 Decrease the phagocytic abilities of macrophages, thereby promoting a pro-tumorigenic macrophage phenotype by secreting soluble factors	[74–76]
Myeloid-derived suppressor cells	Protect against autoimmunity by recruitment of myeloid-derived suppressor cells via CCL2 signalling	[77]