Signaling from the BCR/ABL SH3+SH2 region induces expression of the A1 and pim-1 genes.

(A) 32Dcl3 parental cells (lane 1) or clones expressing WT BCR/ABL (lane 2), STAT5B dominant-active mutant (STAT5B-DAM, lane 3), STAT5B WT (lane 4), BCR/ABLΔΔ (lane 5), BCR/ABLΔΔ, and STAT5B-DAM (lane 6) were starved (8 hours) from IL-3. Expression of the indicated genes was assessed by Northern analysis (upper panel) or Western analysis (lower panel) using specific probes. Equal RNA and protein loading was confirmed by detection of GADPH and actin, respectively. Results represent 3 experiments using cell lines described previously.14 (B) A1 and pim-1 were detected by Western blot assays in total cell lysates obtained from CML-BC cells preincubated with 1 μM STI571 for 24 hours in the presence of IL-3 (upper panel). Inhibition of BCR/ABL kinase activity by STI571 was confirmed by Western blot assay with use of anti-P.Tyr antibodies (lower panel). Results are representative of 2 separate experiments.