Table 1.

VS-4718 sensitized ABCB1-substrate-selected resistant cells to ABCB1 substrates.

Treatment	IC50 ±SDa(RFb)
	KB-3-1 (μM)	KB-C2 (μM)	SW620 (μM)	SW620/Ad300 (μM)
Doxorubicin	0.035 ± 0.002 (1.00)	2.560 ± 0.250 (72.62)	0.061 ± 0.007 (1.00)	5.494 ± 0.600 (90.19)
+VS-4718 (1 μM)	0.030 ± 0.005 (0.85)	0.346 ± 0.128 (9.82)*	0.058 ± 0.012 (0.96)	1.120 ± 0.424 (18.39)*
+VS-4718 (3 μM)	0.026 ± 0.005 (0.74)	0.092 ± 0.007 (2.61)*	0.066 ± 0.004 (1.08)	0.382 ± 0.041 (6.27)*
+Verapamil (3 μM)	0.029 ± 0.007 (0.83)	0.051 ± 0.013 (1.44)*	0.069 ± 0.012 (1.12)	0.356 ± 0.030 (5.84)*
Paclitaxel	0.005 ± 0.001 (1.00)	2.348 ± 0.233 (521.83)	0.028 ± 0.003 (1.00)	2.411 ± 0.687 (86.10)
+VS-4718 (1 μM)	0.004 ± 0.001 (0.97)	0.491 ± 0.031 (109.10)*	0.029 ± 0.005 (1.03)	0.358 ± 0.138 (12.79)*
+VS-4718 (3 μM)	0.003 ± 0.001 (0.67)	0.053 ± 0.018 (11.79)*	0.024 ± 0.002 (0.86)	0.146 ± 0.097 (5.23)*
+Verapamil (3 μM)	0.004 ± 0.001 (0.89)	0.061 ± 0.011 (13.60)*	0.023 ± 0.002 (0.83)	0.100 ± 0.042 (3.57)*
Cisplatin	1.135 ± 0.038 (1.00)	1.921 ± 0.139 (1.69)	1.195 ± 0.094 (1.00)	1.228 ± 0.674 (1.00)
+VS-4718 (1 μM)	1.476 ± 0.007 (1.30)	1.862 ± 0.210 (1.64)	1.272 ± 0.347 (1.06)	1.221 ± 0.119 (0.99)
+VS-4718 (3 μM)	1.462 ± 0.022 (1.29)	2.544 ± 0.145 (2.24)	1.365 ± 0.763 (1.14)	1.490 ± 0.073 (1.21)
+Verapamil (3 μM)	1.113 ± 0.045 (0.98)	2.221 ± 0.162 (1.96)	1.374 ± 0.655 (1.15)	1.474 ± 0.169 (1.20)

^aIC₅₀ values were determined by MTT assay as described in “Materials and Methods,” and were obtained from three independent experiments in triplicate.

^bResistance fold (RF) was calculated from dividing the IC₅₀ values of resistant cells (KB-C2 and SW620/Ad300) by the IC₅₀ of parental cells (KB-3-1 and SW620) in the presence or absence of VS-4718 or positive control inhibitor.

^*indicates p < 0.05 vs. group treated with antineoplastic drug only.