Etoposide-resistance in the multidrug-resistant LZ-8 cells

The multidrug-resistant LZ-8 cells were found to exhibit marked resistance to etoposide compared to wild-type, parental V79 cells. The multidrug resistant phenotype did not significantly contribute to this etoposide-resistance. Following exposure of LZ-8 cells and V79 cells to equivalent concentrations of etoposide, there was a dramatic reduction in the number of etoposide-induced stabilized DNA-topoisomerase II complexes in the LZ-8 cells compared to V79 cells, however, this reduction was not found when nuclei isolated from LZ-8 and V79 cells were exposed to equivalent concentrations of etoposide. These results suggest that cytoplasmic factors are involved in the etoposide-resistance of LZ-8 cells.