CCL2 and neoplasm: Quiescent PSCs can be activated by cytokines such as interleukin and TGF-β, and the activated PSCs secrete soluble cytokines, including IL-10, MCP-1 and VEGF which interact with immune cells in TME, resulting in the increasing the number of immunosuppressive cells and decreasing the infiltration of anti-tumor immune cells in TME.