Downmodulation of STAT5 by RNAi decreases growth of CD34⁺ stem/progenitor cells. (A) Schematic overview of the lentiviral RNAi vectors used in these studies. (B) Transduction efficiency of CD34⁺ CB stem/progenitor cells, performed as indicated in “Lentiviral transductions.” (C) Western blot analysis of STAT5 levels in control (Renilla) or STAT5 RNAi–transduced CD34⁺ cells. Percentages indicate expression of STAT5 relative to control cells, normalized against STAT3 levels. Phospho-STAT3 and -STAT5 levels are shown for the hematopoietic TF-1 cell line. Quantitative Western blot analysis was performed on an Odyssey infrared scanner or using Quantity One imaging software from Bio-Rad. (D) Quantitative PCR for STAT5 mRNA in transduced CB CD34⁺ stem/progenitor cells. STAT5 mRNA was normalized against GAPDH mRNA expression.