Abstract
An adriamycin (ADM)-resistant subline was established by continuous exposure of the SBC-3 cells, a cell line of human small cell lung cancer, to increasing concentrations of ADM, followed by the cloning procedure. The resistant sublines (SBC-3/ADM) thus established were 30-fold more resistant to ADM than the parent SBC-3 cells, in terms of the 70% lethal dose determined by soft agar clonogenic assay. The doubling times of the SBC-3 and SBC-3/ADM cells were 36 h and 22 h, respectively. When transplanted into athymic nude mice, the parent as well as resistant cells formed tumors, and serial passage was successful. Although the transplanted tumors from the two cell lines were very similar in histology, the resistance of the SBC-3/ADM cells to ADM developed in vitro was maintained in serially transplanted tumors. The uptake studies with [3H]daunomycin revealed decreased influx and enhanced active efflux of the drug in the resistant cells, whereas cytogenetic analysis showed that the cell lines had an identical karyotype. These results indicate that ADM resistance may be attributed to alternations in membrane transport, resulting in reduced intracellular accumulation of the drug.
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