In this study, we show that there are a large number of Gr-1+CD11b+ MDSCs in lung tissues of 4T1 tumor-bearing mice, and the number of Gr-1+CD11b+F4/80− granulocytic-MDSCs (PMN-MDSCs) is more than that of Gr-1+CD11b+F4/80+ monocytic-MDSCs (M-MDSCs). The gene discussed is ITGAM; the disease is neoplasm.