CXCR2 inhibition leads to cell cycle arrest in AML cells and inhibits IL8-stimulated signaling cascades. (A) Representative flow plots of THP-1 cells treated with the CXCR2 inhibitor demonstrate a significantly increased percentage of cells in G0 stage. (B-C) Data from 3 independent experiments demonstrate significantly increased G0 cell cycle arrest in THP-1 and U937 cell lines after CXCR2 inhibition (t test, P < .05). (D-F) THP-1 cells were stimulated with IL8 in the presence and absence of CXCR2 inhibitor (10 μm) and immunoblotted for phospho/activated ERK MAP kinase, p38 MAPK, and AKT with appropriate loading controls.