Imatinib sensitivity of regulatory domain mutations in BCR-ABL. SH3-SH2 mutations were introduced into BCR-ABL and stably expressed in Ba/F3 cells. These cell lines were exposed to graded concentrations of imatinib for 4 hours and lysed directly into sodium dodecyl sulfate-polyacrylamide gel electrophoresis loading buffer. Immunoblots were performed for BCR-ABL autophosphorylation, and expression. T212R was the only mutant to display detectable resistance of BCR-ABL autophosphorylation to imatinib.