Inhibition of CXCL4 ligands and CXCR2 signaling reduces cell viability and colony formation in vitro. (A) CD34⁺ enriched cells were transduced with CXCL4 siRNA, and relative scrambled control and level of knock-down (left) and viability (right) measured (n = 3). (B) CD34⁺ cells were treated with increasing concentrations of SB225002 and viable cells analyzed using Annexin V/DAPI staining (left) (n = 3). CFC count was performed in the same cells treated with SB225002 at the concentration indicated (right) (n = 3). (C) CD34⁺38⁻ enriched cells were treated with increasing concentrations of SB225002 and viable cells analyzed using Annexin V/DAPI staining (left) (n = 3). CFC count was performed in cells treated with SB225002 at the concentration indicated (right) (n = 3). Statistical analysis was performed using a paired two-tailed Student t test (*P < .05; **P < .01; ***P < .001). All error bars indicate SEM of the mean. h, human.