Inhibition of cellular tyrosine phosphorylation by STI571 in nonresistant and STI571-resistant K562 cells.

Nonresistant K562 cells were treated for 2 hours with DMSO, 1 μmol/L STI571, and 10 μmol/L STI571 (lanes 1-3). STI571-resistant K562 cells were treated with DMSO, 1 μmol/L, and 10 μmol/L STI571 following continuous culturing in the presence of 0.5 μmol/L STI571 prior to treatments (lanes 4-6), and following STI571 deprivation for 2 hours prior to treatments (lanes 7-9). Immunoblotting of the lysates from these cells was performed with anti-pTyr (upper panel), anti-ABL (middle panel), and anti-SHP2 as a loading control for protein (bottom panel).