The Immunomodulatory Effects of Mesenchymal Stem Cell Polarization within the Tumor Microenvironment Niche

Figure 3

Interactions of MSCs with innate immune cells. MSCs utilize diverse molecular mechanisms to suppress or promote innate immune cells. MSCs suppress macrophage polarization to M1, although they favor M2 polarization. MSCs inhibit NK cell and DC activation, differentiation, and effector functions. MSC-derived PGE2 contributes to all of these effects. MSC-produced IL-6 suppresses neutrophil apoptosis and respiratory burst and also contributes to inhibiting DC function. In the presence of IL-6 and GM-CSF, MSCs also can affect macrophage function, while TGFβ and IDO suppress NK cell function. In addition, MSCs also favor the generation of regulatory DCs. Effects of MSC: + indicates function promotion and − indicates function suppression.