Table 1. MDR phenotype, sensitivity to gemcitabine and sensitivity factors of human cancer cell lines.

Cell line	Origin	MDR phenotype	Doubling time (h)	IC50 (nM) gemcitabine	Sensitivity factor
SW1573	NSCLC	Parental	35±5	17.0±2	1
2R120a		DOX resistant, MRP1	50±6	1.9±1.2	8.9***
2R160a		DOX resistant, P-gP	50±6	0.6±0.4	27.9***
SW1573/S1(1.1)b,c		P-gP transfected	30±2	5.7±2.4	3.0**
SW1573/S1(MRP)b, c		MRP1 transfected	35±8	0.05±0.02	340***
GLC4	SCLC	Parental	22±5	4.1±0.6	1
GLC4/ADRb		DOX resistant, MRP1	31±9	0.4±0.2	11*
A2780	Ovarian	Parental	22±9	1.6±0.3	1
2780ADd		DOX resistant, P-gP	26±8	0.03±0.03	55**
KB3-1	Epidermoid	Parental	16±3	59±24	1
KB8-5e		Colchicine resistant, P-gP	19±5	33.0±20.	1.8 NS
BRO	Melanoma	Parental	21±3	300±87	1
BROmdrf		P-gP transfected	29±4	33±12	9.0**

MDR=multidrug resistance; NSCLC=non-small-cell lung cancer; SCLC=small-cell lung cancer; DOX=doxorubicin; P-gP=P-glycoprotein; MRP=multidrug resistance-associated protein. Cells were exposed to gemcitabine for 72 h. Values represent the mean IC₅₀±s.d. of at least three experiments. IC₅₀=50% growth-inhibiting concentration, sensitivity factor; IC₅₀ parental/IC₅₀ MDR variant. Statistical analysis by t-test (independent samples); NS=not significant.

^*P<0.05.

^**P<0.01.

^***P<0.001. References:

^aKuiper et al (1990).

^bZaman et al (1993).

^cZaman et al (1994).

^dLouie et al (1986).

^eShen et al (1986).

^fLincke et al (1990).