Inverse correlation between Gfi-1B and Bcl-xL expression in response to imatinib treatment. (A) K562 cells treated with imatinib for the indicated periods were processed for RT-PCR analysis (left panel) using primers specific for Gfi-1B, Bcl-xL, and the GAPDH gene and for Western blotting (right panel) with anti-Gfi-1B, anti-Bcl-xL, and β-tubulin antibody. (B) Densitometric analysis of Gfi-1B and Bcl-xL at the RNA (left panel) and protein (right panel) levels, with results normalized by the GAPDH mRNA level and the β-tubulin level, respectively, in each sample.