PSCs were found to produce myeloid-derived suppressor cell (MDSC)-promoting cytokines (interleukins, IL-6; VEGF; macrophage colony-stimulating factor, M-CSF) and chemokines (SDF-1, MCP-1) to promote differentiation of immune cells into the functional MDSC phenotypes to prevent innate or adaptive immune responses against cancer cells, among which IL-6 was the key factor contributing to STAT3 signaling and MDSC differentiation [30]. Here, IL6 is linked to cancer.