Figure 5.

Influence of hydroxyurea and pan-JAK inhibitor INC424 on the phenotypes of MPN cells. Stable, inducible Ton.JAK2.V617F and Ton.JAK2.WT cells were treated with 1 μg/mL doxycycline for 6 days and then exposed to various concentrations of hydroxyurea or INC424 for 72 h. The drug concentrations that inhibited cell growth by 50% (IC₅₀) and 90% (IC₉₀) were determined by the XTT assay. (A) The viability of Ton.JAK2.V617F cells plotted against various concentrations of hydroxyurea. (B) Western blot analysis on various proteins of the Ton.JAK2.V617F cells treated with or without hydroxyurea at the concentration of 5.55 μg/ml (the IC₅₀ concentration for HU in these cells) for 3 days. (C) The viability of Ton.JAK2.WT (left panel) and Ton.JAK2.V617F (right panel) cells plotted against various concentrations of INC424. (D) Western blot analysis on various proteins of the Ton.JAK2.WT and Ton.JAK2.V617F cells treated with or without INC424 at the concentration of either IC₅₀ or IC₉₀ for 3 days. (E) Effects of various concentrations of INC424 on the expression of let-7a and Hmga2 in Ton.JAK2.WT and Ton.JAK2.V617F cells. Cells were harvested for qRT-PCR analysis at 3 days after treatment with the drug at indicated concentrations. The error bars show the standard deviation of three independent experiments. Asterisks indicate statistical significance (t-test; *P<0.01; **P<0.001; ***P<0.0001). WT: wild-type; HU: hydroxyurea; Conc: concentration.