Table 1: IC50 values (mean ± SEM) of shikonin for a panel of 15 different sensitive and resistant cancer cell lines after 24and 48 h as assayed by resazurin reduction assay.

Cell line Cancer type Shikonin IC50 [μM] (24 h) IC50 [μM] (48 h) U937 Histiocytic leukemia cell line 0.30 ± 0.003 0.19 ± 0.003 CCRF-CEM Acute lymphocytic leukemia cell line 0.37 ± 0.01 0.24 ± 0.001 CEM/ADR5000* Acute lymphocytic leukemia cell line 0.36 ± 0.05 0.38 ± 0.01 HL-60 Acute myelocytic leukemia cell line 0.39 ± 0.01 0.42 ± 0.001 HL-60/AR* Acute myelocytic leukemia cell line 0.95 ± 0.003 0.47 ± 0.001 MCF-7 Breast carcinoma cell line 9.05 ± 0.08 10.51 ± 0.03 SK-BR-3 Breast adenocarcinoma cell line 9.21 ± 0.08 8.70 ± 0.03 MDA-MB-231/pcDNA3 Breast carcinoma cell line 1.23 ± 0.03 0.88 ± 0.03 MDA-MB-231/BCRP* Breast carcinoma cell line 2.61 ± 0.06 1.48 ± 0.04 786-O Kidney carcinoma cell line 9.44 ± 0.13 8.03 ± 0.06 SW-1116 Colorectal carcinoma (GIII) cell line 6.63 ± 0.09 4.42 ± 0.06 HCT-116 Colorectal carcinoma 4.74 ± 0.07 8.54 ± 0.01 SW680 Colorectal carcinoma 7.21 ± 0.13 2.96 ± 0.06 Capan1 Pancreas adenocarcinoma cell line 7.23 ± 0.28 6.21 ± 0.14 SUIT-2 Pancreatic carcinoma cell line 12.92 ± 0.35 18.50 ± 0.09

*MDR cancer cell lines with various drug resistances.