MDSCs interact within the TME mainly through the following mechanisms: (1)Recruitment signals: Tumor cells and stromal cells secrete factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), VEGF, and chemokine (C-C motif) ligand 2 (CCL2) to recruit MDSCs into the TME (34–36). Here, CCL2 is linked to neoplasm.