Withaferin A (WA) has no apparent suppressive effect on the growth of normal bone marrow CD34‐positive cells in the short‐term culture. (a) Normal human bone marrow CD34‐positive cells (n = 3), MDS‐L and MDS92 (CD34‐positive fraction) cells were treated with the indicated concentrations of WA for 24 and 48 h, and cell count was assessed by trypan blue dye exclusion assay. The data represent the mean values with SD from three independent experiments. (b) Normal human bone marrow CD34‐positive cells (n = 3) and MDS92 (CD34‐positive fraction) cells were treated with the indicated concentrations of WA for 24 and 48 h, and cytospin preparations were stained by May–Gruenwald–Giemsa (original magnification ×400). Representative images for each treatment are shown. (c, e) The cell cycle analyses by PI staining are shown. Human normal bone marrow CD34‐positive cells (sample 1 and sample 2) and MDS92 (CD34‐positive fraction) cells were treated with indicated concentrations of WA for 24 h, and the cells were stained with PI and analyzed by flow cytometry. Representative histogram patterns for each treatment are shown. (d) From the data of two normal CD34‐positive cells shown in (c), the cell fractions at G1, S and G2⁄M phase are presented by white, gray and black bars, respectively. (f) From the data of MDS92 cells shown in (e), the cell fractions at G1, S and G2⁄M phase are presented by white, gray and black bars, respectively. The data represent the mean values with SD from three independent experiments.