Induction of multidrug resistance (MDR) by transfection of MCF‐10A cell line with c‐Ha‐ras and c‐erbB‐2 oncogenes

Abstract
To investigate the relationship between oncogene activation and appearance of multidrug resistance (MDR) we transfected the human breast epithelial cell line MCF‐10A, negative for the expression of the P‐glycoprotein, with c‐Ha‐ras and/or c‐erbB‐2 oncogenes. The appearance of the MDR phenotype was then studied by evaluating mdr‐1 mRNA expression, the presence of P‐glycoprotein on the cell membrane and the onset of doxorubicin resistance, together with the effect of the reversing agent verapamil. We found that only MCF‐10A transfected with both c‐Ha‐ras and c‐erbB‐2 oncogenes acquired the MDR phenotype.