Table 3 Immunosuppressive effects of MSCs on several immune cell types which contribute to tumor progression

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

[62,63,64]

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, 67,68,69,70]

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

[70,71,72,73]

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

[74,75,76]

Myeloid-derived suppressor cells

Protect against autoimmunity by recruitment of myeloid-derived suppressor cells via CCL2 signalling

[77]