Jak2S523L-expressing Ba/F3 cells coexpressing EPOR or MPL cells are sensitive to treatment with ruxolitinib. (A) Proliferation with increasing concentration of ruxolitinib relative to proliferation in the presence of dimethyl sulfoxide (DMSO) control is depicted for Ba/F3 cells transduced with MPL coexpressing either Jak2 WT, Jak2S523L, Jak2V617F, or Jak2K539L. Data are depicted as means ± standard errors of the mean (SEMs). (B) Proliferation with increasing concentration of ruxolitinib relative to proliferation in the presence of DMSO control is depicted for Ba/F3 cells transduced with EPOR coexpressing either Jak2 WT, Jak2S523L, Jak2V617F, or Jak2K539L. Data are given as means ± SEMs. (C) WB analysis. Ruxolitinib treatment for 4 hours at 1 µM inhibits pStat5, pAkt, and phosphorylated mitogen-activated protein kinase (pMapk) signaling in Ba/F3 cells transduced with MPL coexpressing either Jak2 WT, Jak2S523L, Jak2V617F, or Jak2K539L. (D) WB analysis. Ruxolitinib treatment for 4 hours at 1 µM inhibits pStat5, pAkt, and pMapk signaling in Ba/F3 cells transduced with EPOR coexpressing either Jak2 WT, Jak2S523L, Jak2V617F, or Jak2K539L.