Isoform-specific inhibition of STAT5 in human cell lines.

<p>(A) K562 cells were lentivirally transduced with shRNAs targeting control (shGL2), human STAT5A (sh-huS5A), human STAT5B (sh-huS5B), and a mixture of both. Four days after transduction protein expression of both STAT5 isoforms and ERK2 was analyzed by western blotting. The numbers indicate changes in protein expression in % as determined by densitometry. (B) The human BCR-ABL-positive cell lines EM-2, K562 and LAMA-84 were lentivirally transduced with control (shGL2), isoform-specific (sh-huS5A, sh-huS5B), and a mixture of both isoform-specific shRNAs. Four days after transduction, equal numbers of cells were plated and the number of viable cells was determined after additional four days by Trypan-blue dye exclusion. The number of viable non-transduced cells (native) was set 100%. The data represent mean of four independent experiments. (C) Impact of isoform-specific STAT5 shRNAs on imatinib mesylate (IM) response as determined by IC50. STAT5 shRNAs were compared to GL2 controls with * p<0.05 and ** p<0.01.