Dose-dependent rescue by cytokines of Jak2^V617F shRNA-induced cell growth inhibition. (A) UKE-1 and SET-2 cells were infected with the pRRL-mt4 or the control pRRL-Scr virus, selected for GFP expression, and plated in liquid culture in the absence or the presence of increasing concentrations of IL-3, TPO, or GM-CSF (expressed in nanograms per milliliter). Results [mean values (± SEM)] of 2 independent experiments from day 9 of culture are presented. *P ≤ .05. (B) Effect of IL-3 or TPO exposure on the phosphorylation levels of STAT5 in UKE-1 cells infected by the pRRL-mt4 or the control pRRL-Scr virus and cultured for 6 days with or without IL-3 (30 ng/mL) and TPO (10 ng/mL). Data indicate that rescue by cytokines could be mediated through signaling of the residual JAK2^V617F protein, remaining after shRNA action, detected with this Western blot analysis.