TABLE 1

Effect of dLop and Lop on the cytotoxicity of drugs preferentially effluxed by P-gp, Mrp1, and BCRP

IC₅₀ values are mean ± S.D. from three independent experiments.

Cell Line	Cytotoxic Drug	IC₅₀	RR	Cytotoxicity
				dLop (20 μM)		Lop (20 μM)
				IC₅₀	RR	IC₅₀	RR
B1 resistant	Doxorubicin	846 ± 68 nM	71	234 ± 57 nM	20^*	144 ± 15 nM	12^*
B1 parental	Doxorubicin	12 ± 4 nM
C1 resistant	Etoposide	79 ± 20 μM	79	140 ± 41 μM	140^†	169 ± 73 μM	169^†
C1 parental	Etoposide	1 ± 1 μM
G2 resistant	Mitoxantrone	223 ± 54 nM	37	256 ± 56 nM	42	367 ± 118 nM	61
G2 parental	Mitoxantrone	6 ± 1 nM

RR, resistance ratio, which is the quotient of the IC₅₀ value of the resistant cell line to that of the parental line.
↵* P < 0.001 (α = 0.05, from initial IC₅₀ value of resistant cell line) by Student's two-tailed t-test.
↵† P > 0.18.