The Role of GATA1s in DS AMkL Figure 2. Down-regulation of GATA1s in CMK cells results in increased differentiaion toward megakaryocytic lineage. Megakaryocytic cell surface marker expression in the CMK-5a, -5b, and -neg stable clones was determined by flow cytometry. The unshaded plot represents isotype control. Numbers (isotype ratio) represent the ratio between the quantitative expression value of the cell surface marker and isotype control. doi:10.1371/journal.pone.0027486.g002 Figure 3. The effects of GATA1s on ara-C sensitivity in CMK cells. Panel A: The CMK-5a, -5b, and -Neg cells were cultured in complete medium with dialyzed fetal bovine serum in 96-well plates at a density of 86104 cells/ml, with a range of concentrations of ara-C at 37uC, and viable cell numbers were determined using the Cell Titer-blue reagent and a fluorescent microplate reader. The IC50 values were calculated as the concentrations of drug necessary to inhibit 50% growth compared to control cells cultured in the absence of drugs. The data are presented as mean values 6 standard errors from at least 3 independent experiments. Panel B: Soluble proteins from the CMK-5a, -5b, and –neg sublines were subjected to Western blotting and probed by anti-hENT1, -dCK, or b-actin antibodies. Panel C: Basal apoptosis in the CMK-5a, -5b, and –neg cells was determined by annexin V/PI staining and flow cytometry analysis, as described in the Materials and Methods. * and ** indicate p,0.05 and 0.005, respectively. doi:10.1371/journal.pone.0027486.g003 PLoS ONE | www.plosone.org 5 November 2011 | Volume 6 | Issue 11 | e27486