Cellular and karyotypic characterization of two doxorubicin resistant cell lines isolated from the same parental human leukemia cell line

Abstract

Separate mechanisms underlying the multidrug resistant (MDR) phenotype were identified in 2 independent approaches to select tumour cells resistant to low concentrations of doxorubicin (Dox) from the sensitive T cell leukemia cell line CCRF‐CEM. The CEM/A7 cell line was selected at an initial concentration of 0.005 μg/ml of Dox and maintained at 0.07 μg/ml. In contrast, the CEM/A5 line was selected using an initial concentration of 0.01 μg/ml and maintained in Dox at a concentration of 0.05 μg/ml. P‐glycoprotein expression was demonstrated in the CEM/A7 line but not the CEM/A5 line. Amplification of the mdr1 gene was not observed in the CEM/A7 cell line. Both cell lines showed cross‐resistan..