Molecular analysis of doxycycline-independent tumors. (A) Western blot analysis to detect expression of BCR/ABL in representative doxycycline-independent tumor cell lines grown in the absence or presence of doxycycline. Constitutive cABL expression is also shown. (B) Immunoprecipitation/Western blot analysis of downstream signaling from doxycycline-independent tumor cells. Protein lysates from doxycycline-independent tumor cell lines grown in the absence of IL-3 and doxycycline were immunoprecipitated with an anti-phosphotyrosine antibody followed by Western blot analysis with the same antibody (P-TYR/P-TYR). Parental TonB210.1 cells grown in the presence of doxycycline were also analyzed (1(P) +DOX). Size markers are indicated at right.