Table 1. IC₅₀ profile of all the parental cells and the drug-resistant cells to shikonin analogues.

	Shikonin and analogues/µM
Cell lines	SHK	DS	IBS	DMAS	AS	IVS	MBS
K562	0.93±0.03	1.24±0.20	0.46±0.01	0.45±0.01	0.45±0.02	0.46±0.02	0.46±0.01
K562/Shk	1.82±0.03*** (1.96)	1.03±0.05	0.47±0.01	0.46±0.01	0.54±0.08	0.46±0.01	0.47±0.03
K562/Shk-Dox	0.90±0.02	1.58±0.18	0.47±0.01	0.45±0.04	0.84±0.03*** (1.87)	0.44±0.02	0.46±0.01
K562/Adr	0.95±0.03	1.04±0.06	0.59±0.02	0.56±0.07	0.51±0.12	0.60±0.04	0.49±0.06
K562/Adr-Shk	1.96±0.05*** (2.06)	1.46±0.09** (1.40)	0.49±0.01** (0.83)	0.48±0.01	0.46±0.01	0.73±0.03*(1.22)	0.43±0.08
MCF-7	1.52±0.07	0.86±0.04	1.03±0.03	0.83±0.01	0.99±0.02	0.88±0.01	0.98±0.03
MCF-7/Shk	3.09±0.07*** (2.03)	0.88±0.05	1.17±0.07* (1.13)	0.94±0.03** (1.13)	1.20±0.12	0.94±0.04	1.21±0.07* (1.23)
MCF-7/Shk-Dox	1.72±0.82	0.69±0.04*(0.80)	0.56±0.03*** (0.54)	0.87±0.03	1.24±0.04** (1.25)	0.85±0.03	0.90±0.01* (0.92)

The inhibitory effect of shikonin analogues on drug-sensitive and -resistant cells was determined by MTT assay as described in the Material and Methods section.

^*, p<0.05, statistical significance in comparison to parental cell line K562, K562/Adr or MCF-7.

Numbers in parenthesis are the drug-resistance fold (IC₅₀ of drug-resistant cells/IC₅₀ of the parental drug-sensitive cells).