Figure 3

STAT5a plays important role in hTERT mRNA expression. (a) HL60 and K562 cells were treated with vehicle (DMSO) or STAT5 inhibitor (50 μM) for 48 h, after that cells were harvested. Expression of hTERT was measured using real-time PCR and normalized to the expression of GAPDH. TA was determined by quantitative telomerase assay. (b) K562 cells were co-transfected with empty vector (pGL3) or with a luciferase construct containing the hTERT promoter (pGL3-hTERT) together with empty expression vector (pMX) or STAT5a or STAT5b expression construct (pMX-STAT5a or pMX-STAT5b). Luciferase activity was determined 48 h after transfection and was normalized to empty expression vector. Each luciferase assay was repeated 3 times. (c) K562 cells were transfected with Scramble siRNA (non-targeting siRNA), STAT5a siRNA, STAT5b siRNA, or non-transfected (Mock). Cells were lysed after 72 h post-transfection. Total amount of STAT5a, STAT5b and hTERT were shown by Western blotting, and quantitated by normalization over the expression of β-Actin using ImageJ. (d) After 72 h post-transfection, K562 cells were collected and hTERT mRNA expression level and TA were measured by real-time PCR and quantitative telomerase assay, respectively