Effect of SCF and of various cytokines on the proliferation of the 2 different ROSA cell lines. (A) ROSA^{KIT WT} or ROSA^{KIT D816V} cells were treated or not treated with rhSCF (80 ng/mL) for 4 days at 37°C. At each time point, 10 μL of 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was added in corresponding wells, and the cells were incubated for 3 additional hours in an incubator at 37°C. The number of living cells was then measured for each condition by reading the absorbance at 570 nm. (B) ROSA^{KIT WT} (with or without SCF) or ROSA^{KIT D816V} cells (without SCF) were treated with various cytokines (all at 100 ng/mL) for 3 days. At that time, 10 μL of MTT was added in corresponding wells, and the cells were incubated for 3 additional hours in an incubator at 37°C. The number of living cells was then measured for each condition by reading the absorbance at 570 nm. Data presented are the mean ± standard deviation (SD) from 3 independent experiments. OD, optical density.