Table 1.

Determination of the IC₅₀ values of different anticancer drugs

Drugs	IC50 (µg/ml)		RF	IC50 (µg/ml)		RF
	MCF-7	MCF-7/DOX		ZR-75-30	ZR-75-30/DOX
DOX	0.37±0.03	6.58±1.50	17.59	0.70±0.03	16.88±5.64	24.11
DDP	3.01±0.59	10.77±1.91	3.59	4.78±1.77	9.28±1.15	1.94
CTX	5.59±1.28	37.89±3.94	6.79	2.26±0.83	15.26±1.56	6.74
TAM	4.25±0.29	12.19±2.64	2.87	3.45±0.23	17.65±2.36	5.12

Notes: IC₅₀ values of anticancer drugs were determined in MCF-7 and ZR-75-30 cells and the corresponding drug-resistant MCF-7/DOX and ZR-75-30/DOX cells. The cells were treated with various concentrations of DOX, DDP, CTX and TAM for 24 h. The IC₅₀ values and the RFs were evaluated. The data are expressed as the mean ± SD of three independent experiments. Abbreviations: IC₅₀, half maximal inhibitory concentration; DOX, doxorubicin; DDP, cis-Dichlorodiamineplatinum; CTX, cyclophosphamide; TAM, tamoxifen; RF, resistant fold.