Tumor-derived factors (colony-stimulating factors, proinflammatory cytokines, and others) can regulate the differentiation of HSCs and HPCs in the bone marrow and subsequently contribute to the accumulation of MDSCs.130–133 MDSCs are defined as a group of immature CD11b+GR1+ cells that inhibit tumor-specific immune responses, which include precursors of macrophages, granulocytes, dendritic cells (DCs) and myeloid cells.134 Two main MDSC populations have been characterized: monocytic MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs). This evidence concerns the gene ITGAM and neoplasm.