STI571 inhibits constitutive STAT5 activation andcis gene expression in primary hematopoietic cells from animals with the CML-like illness.
(A) Protein lysates from either peripheral blood granulocytes (B) or whole BM cells obtained from placebo-treated (2B, 3B) or STI571-treated (1A, 3A, 4A) mice were analyzed by immunoblot with an antibody recognizing activated STAT5 (pSTAT5, upper panel), or an antibody against the amino-terminal region of STAT5, which recognizes both full-length STAT5A/B and carboxy-terminal isoforms of STAT5 (lower panel). As a control, lysates from wild-type (WT) or P210BCR/ABL–expressing (B/A) 32D cells are shown at left. The positions of full-length STAT5A and STAT5B (p96 and p94, respectively) and the truncated forms of each (p80 and p77, respectively) are shown at the arrows. (B) Total RNA from spleen (lanes 2,4,7), blood (lanes 1,6), and BM (lanes 3,5,8) from either placebo-treated (control) or STI571-treated mice with the CML-like illness was analyzed by Northern blot by means of the indicated radiolabeled DNA probe. Location of the STAT5-responsive genecis15 and control glyceraldehyde-3-phosphate dehydrogenase are indicated at the arrows. Total BM RNA from secondary BM transplant recipients with the CML-like illness, treated (lane 10) and untreated (lane 9) with STI571, is shown at right. As a control, RNA from the myeloid cell line 32D expressing P210BCR/ABL (B/A) or retroviral vector alone (N) is shown at far right. Lanes 3, 4, and 6-8 represent samples from different tissues from the same animals.
