S100A9 induces differentiation of primary human AML cells. (A) RNA expression of TLR4, S100A8, and S100A9 in primary human AML samples in the Leucegene cohort. Each dot represents 1 patient: orange, myelomonocytic and monocytic AMLs (French-American-British [FAB] M4 and M5); blue, undifferentiated AML (FAB M0 and M1). (B) Flow cytometry analysis of TLR4 expression on primary AML cells. Top 3, M0 and M1; bottom 3, M4 and M5. (C) Intracellular staining of S100A8 and S100A9 in primary human AML cells evaluated by flow cytometry. (D) Flow cytometry analysis of myeloid cell surface markers CD11b and CD14 of primary human AML cells, M0 and M1 vs M4 and M5, stimulated with rhS100A9 (20 µg/ml) for 48 hours. (E) CD11b⁺CD14⁺ cells in primary human cells from FAB M0 and M1 (left) and FAB M4 and M5 (right) patients after S100A9 stimulation (n = 10 per group). Data are expressed as the mean ± standard error of the mean. *P < .05. ns, not significant.