HXR9 selectively inhibits proliferation and promotes apoptosis of MONOMAC-6 cells. (A) Cell proliferation assay after the treatment with CXR9 or HXR9 at the concentration of 0, 5, 10, and 20μM, respectively, for 6, 24, or 48 hours (h). Cells were counted at indicated time points and the cell number was normalized with that before peptide treatment. Mean ± SD values from 2 independent experiments are shown. (B) Cell viability assay after the treatment with CXR9 or HXR9 at the concentration of 0, 1, 5, 10, 20, 25, 30, and 60μM, respectively, for 24 hours. Cell viability was measured with MTS assay. Mean ± SD values from 3 independent experiments are shown. (C) Cell apoptosis assay after the treatment with CXR9 or HXR9 at the concentration of 5, 10, and 20μM, respectively, for 24 hours. Apoptosis was measured by flow cytometry analysis of MONOMAC-6 cells stained with FITC-labeled annexin V and counterstained with PI. Percentage of cells is shown in the corner of each quadrant. Results are representatives of 3 independent experiments. (D) Cells were transfected with PBX3 siRNA oligos (ie, siPBX3) or scrambled oligos (ie, NC) and then treated with CXR9 or HXR9 at the concentration of 0, 1, 5, 10, 15, and 20μM, respectively. Cell viability was measured with MTS assay 24 hours after treatment. Mean ± SD values from 2 independent experiments are shown.