Table 1.

IC₅₀ (µM) values and fold decrease in drug sensitivity (RI) of parental (CEM) versus resistant (CEM-VCR R and CEM/2ME2 28.8R) human acute lymphoblastic leukemia cell lines treated with microtubule targeting agents

IC50 (µM) ± SDa				Resistance Index (RI)b
Compound	CEM	CEM-VCR R	CEM/2ME2-28.8R	CEM-VCR R:CEM	CEM/2ME2-28.8 R:CEM
Vincristine	0.08 (± 0.05)	8.11 (± 1.62)	0.41 (± 0.19)	101.4 < 0.05	5.1 > 0.05
Vinblastine	0.13 (± 0.06)	1.12 (± 0.16)	0.39 (± 0.13)	8.6 < 0.05	3.0 > 0.05
2-Methoxy-estradiol	0.08 (± 0.04)	4.07 (± 1.34)	8.52 (± 1.38)	50.9 < 0.05	106.5 < 0.05
Colchicine	0.32 (± 0.21)	1.01(± 0.36)	0.56 (± 0.19)	3.2 < 0.05	1.8 > 0.05
Paclitaxel	0.15 (± 0.09)	1.11 (± 0.36)	0.25 (± 0.12)	7.4 < 0.05	1.7 > 0.05
HMB-isatin	1.02 (± 0.32)	1.07 (± 0.37)	1.29 (± 0.41)	1.0 > 0.05	1.3 > 0.05
I4M-isatin	1.07 (± 0.44)	1.26 (± 0.19)	1.16 (± 0.46)	1.2 > 0.05	1.1> 0.05
N2M-isatin	0.36 (± 0.19)	0.49 (± 0.36)	0.46 (± 0.32)	1.4 > 0.05	1.3 > 0.05

^aValues are the mean of three independent experiments, performed in triplicate (n = 9) ± SD

^bThe RI was calculated to determine the degree of acquired resistance of each cell line to the various drug treatments and was determined using the following equation:$RI=\frac{IC50\left(resistantsubline\right)}{IC50\left(sensitivesubline\right)}$. P-values < 0.05 were considered significant