TABLE 1

ABC transporter expression confers resistance to TKIs

IC₅₀ values (nanograms per milliliter for romidepsin, micromolar concentration for topotecan) were determined by the sulforhodamine B assay as described under Materials and Methods. In combination assays, imatinib was used at a concentration of 5 μM and nilotinib at a concentration of 1 μM.

	HEK pcDNA3.1	HEK ABCB1	HEK ABCG2	RR^{^a}
Romidepsin	0.0026 ± 0.0013	2.5 ± 1.1		961
Romidepsin + imatinib	0.0012 ± 0.00050	0.28 ± 0.29		108
Romidepsin + nilotinib	0.0017 ± 0.0011	0.0048 ± 0.0020		1.8
Topotecan	0.036 ± 0.016		0.72 ± 0.39	20
Topotecan + imatinib	0.027 ± 0.024		0.016 ± 0.0035	0.4
Topotecan + nilotinib	0.032 ± 0.0065		0.026 ± 0.0065	0.7

RR, relative resistance.
↵a RR values were calculated by dividing the IC₅₀ of the transporter-expressing cells by the IC₅₀ of the empty vector-transfected cells.