Many chemokines have been involved in MDSCs generation and recruitment to primary tumor sites or pre-metastatic niches, such as CXCL1, CXCL2, CXCL5, CXCL12, GM-CSF, G-CSF, M-CSF, VEGF, IL-6, IL-1ß or ß-FGF (46). Here, CSF2 is linked to neoplasm.