Finally, we detected the expression of marker genes of macrophage and NK cells, and found that five genes of FCAR, FCGR3A, PREX1, S100A8 and S100A9 all were significantly overexpressed in the leukemia cells of HAP1 compared with that in the normal stroma cells of HS-5 (p < 0.05, Fig. 9A). Here, S100A9 is linked to leukemia.