Induction of STAT5 reporter gene activity with Bcr/Abl.

(A) Ba/F3p210 cells and untransformed Ba/F3 cells in RPMI plus WEHI (10%) were transfected with the β-casein luciferase reporter gene (together with the β-GAL construct). Twelve hours after transfection, cells were split and maintained in either the presence or absence of Bcr/Abl kinase inhibitor STI571 (1 μmol/L). Cells were then harvested, and lysates were assayed for luciferase and β-GAL activities, expressed as a ratio of luciferase activity to β-GAL-activity. Ba/F3p210 cells expressed significantly more STAT5 reporter gene activity than did Ba/F3 cells, and the increased STAT5 activity was due directly to Bcr/Abl, since it could be abrogated by Bcr/Abl kinase inhibitor STI571. (B) Untransformed Ba/F3 cells and TonB.210 cells were transfected with the β-casein luciferase reporter gene (together with the β-GAL construct). Twelve hours after transfection, cells were split, maintained in either the presence or absence of doxycycline (1 μg/mL), and assayed for luciferase and βGAL activities. Induction of Bcr/Abl in Ton B.210.1 cells by doxycycline increased STAT5 reporter gene activity. Doxycycline had no effect on STAT5 reporter gene activity in untransformed Ba/F3 cells.