Constitutive signaling by JAK2 V617F induces miR-28 expression. (A) miR-28 relative expression was measured in the HEL and UKE-1 cell lines, which are homozygous for JAK2 V617F and in UT-7 parental cell line, which is negative for JAK2 V617F. The JAK2 V617F and WT expression levels are reported under the histograms. (B) miR-28 relative levels were assessed in UT-7 parental cell line transduced with a bicistronic retrovirus expressing the GFP along with either JAK2 WT or JAK2 V617F and sorted for equivalent GFP levels. *P < .01. (C) Ba/F3 cells were stimulated with 20 ng/mL IL-3 for 3 hours. Ba/F3 EpoR and Ba/F3 TpoR cells coexpressing equivalent JAK2 WT or JAK2 V617F levels (sorted cells) were stimulated for 3 hours with 20 units/mL Epo or 20 ng/mL Tpo, respectively.