Analysis of downstream signaling of BCR/ABL through STAT5 in doxycycline-dependent (A) and -independent (B) cells. (A) Protein lysates from serum-starved doxycycline-dependent TonB210.1 cells in the absence of doxycycline and without IL-3 stimulation (−DOX/−IL3), absence of doxycycline pulsed with IL-3 (−DOX/+IL3), or presence of doxycycline in the absence of IL-3 stimulation (+DOX/−IL3) were immunoprecipitated with an anti-STAT5 antibody followed by Western blot analysis with an anti-phosphotyrosine antibody (STAT5/P-TYR). Blots were stripped and reprobed with an anti-STAT5 antibody (STAT5/STAT5). Total lysates were also Western blotted with an anti-ABL antibody (/ABL) for detection of BCR/ABL and constitutive cABL expression. (B) Protein lysates from doxycycline-independent tumor cell lines grown in the absence of IL-3 and doxycycline were immunoprecipitated with an anti-STAT5 antibody followed by Western blot analysis with an anti-phosphotyrosine antibody (STAT5/P-TYR). Parental TonB210.1 cells grown in the presence of doxycycline were also analyzed (1(P) +DOX). Blots were stripped and reprobed with an anti-STAT5 antibody (STAT5/STAT5). Total lysates were also Western blotted with an anti-ABL antibody (/ABL) for detection of BCR/ABL and constitutive cABL expression.