CSF2 and neoplasm: Tumor cells can produce various cytokines (mainly including GM-CSF, granulocyte-macrophage colony-stimulating factor, and CXCL2, chemokine ligand 2), resulting in an immunosuppressive environment through recruiting myeloid-derived suppressor cells (MDSCs) and thus inhibit the functions of tumor-specific CD8+ T cells and cause tumor cells’ immune escape (9, 10).