BCR-ABL expression in AR230 and LAMA84.

(A) Northern blot analysis of BCR-ABL (with an ABLprobe) and β-actin (loading control) mRNA in the sensitive and resistant cells. Densitometric analysis of the BCR-ABL/actin ratio showed a 1.6- and a 5.5-fold increase in AR230-r and LAMA84-r, respectively, compared with their sensitive parental lines. (B) Western blot probed with anti-Abl (upper part of the filter) and anti-actin (lower part of the filter) antibodies. Bcr-Abl overexpression in relation to the sensitive counterparts was estimated by densitometry of the Bcr-Abl/actin ratio as 6-and 12-fold in AR230-r and LAMA84-r, respectively; these values were reduced to 1.5- and 5.6-fold, respectively, 7 days after withdrawal of STI571 from the culture. (C) Western blot probed with anti-Bcr (upper part of the filter) and anti-actin (lower part of the filter) antibodies. CML-T1, which does not express normal Bcr protein, and KCL22, which does, were used as negative and positive controls, respectively. LAMA84-r overexpresses both Bcr (160 kd) and Bcr-Abl (210 kd) compared withA84-s. LAMA84-r* corresponds to the subline maintained in culture without STI571 for 1 week, in which reductions in Bcr-Abl and Bcr expression can be observed. AR230-r cells express a lower level of Bcr protein than AR230-s in spite of the Bcr-Abl overexpression.