Table 2. GI₅₀ values for vincristine in the presence of verapamil, Nutlin-3, NDD0005, MI-63 and RG7388 in p53 mutant high MDR-1-expressing SKNBe2C and low MDR-1-expressing SKNAS, and p53 wt high MDR-1-expressing SHSY5Y neuroblastoma cells and the fold potentiation relative to vincristine alone.

		72 h GI50 of vincristine (nM)			Fold potentiation
Compound	Cell line	1 μM/0.25 × a	2 μM/0.5 × a	5 μM/1 × a	1 μM/0.25 × a	2 μM/0.5 × a	5 μM/1 × a
	SKNBe2C	4.2±0.6	2.2±0.3	1.1±0.2	10.5	19.9	38.2
					P<0.05	P<0.05	P<0.05
Verapamil	SKNAS	1.2±0.1	1.1±0.1	0.9±0.1	1.1	1.1	1.3
					P=0.259	P=0.185	P=0.121
	SHSY5Y	0.5±0.2	0.2±0.1	<0.1 nM	10.2	21.8	>50
					P<0.001	P<0.001	P<0.001
	SKNBe2C	20.1±6.2	3.1±1.5	1.0±0.2	2.1	13.7	43.7
					P<0.05	P<0.005	P<0.005
Nutlin-3	SKNAS	1.4±0.3	1.5±0.6	1.5±0.7	1.3	1.2	1.2
					P=0.321	P=0.109	P=0.225
	SHSY5Y	2.4±0.2	1.9±0.4	1.4±0.3	2.1	2.8	3.7
					P<0.05	P<0.05	P<0.01
	SKNBe2C	2.2±0.5	1.2±0.2	0.7±0.2	13.0	23.5	42.4
					P<0.05	P<0.05	P<0.05
NDD0005	SKNAS	1.0±0.1	0.8±0.1	< 0.1	1.2	1.4	ND
					P=0.1	P<0.05	ND
	SHSY5Y	2.3±0.7	0.5±0.1	0.2±0.1	2.4	12.0	33.1
					P<0.05	P<0.05	P<0.05
	SKNBe2C	22.8±3.2	3.1±0.6	1.0±0.1	1.92	13.9	44.4
					P<0.001	P<0.01	P<0.01
MI-63	SKNAS	1.1±0.2	1.0±0.1	0.9±0.1	1.2	1.3	1.4
					P=0.664	P=0.377	P=0.242
	SHSY5Y	3.9±0.8	1.8±0.6	0.6±0.1	1.3	2.9	9.5
					P=0.096	P<0.001	P<0.01
	SKNBe2C	14.6±2.2	18.8±2.2	2±0.3	1.8	1.4	13.3
					P=0.073	P=0.39	P=0.052
RG7388	SKNAS	1.2±0.1	1±0.002	0.9±0.1	1.0	1.1	1.2
					P=0.532	P=0.078	P=0.06
	SHSY5Y	2.6±0.4	2.3±0.2	1.1±0.5	2.0	2.2	4.8
					P<0.05	P<0.05	P<0.01

Abbreviations: MDR-1=Multi-Drug Resistance Protein 1; ND=not determined.

Values represent average±s.e.m.

^aFor p53 mutant cells, verapamil, Nutlin-3, NDD0005, MI-63 and RG7388 were used at 1, 2 and 5 μM in combination with vincristine. For p53 wt cells, verapamil was used at 1, 2 and 5 μM in combination with vincristine, whereas Nutlin-3, NDD0005, MI-63 and RG7388 were used in combination at 0.25 × , 0.5 × and 1 × GI₅₀ concentrations.