Fig. 1

Cytotoxic effect of As^III and Tetra, alone or in combination, against human breast cancer cell line MDA-MB-231. Cell viability was determined by XTT assay after the treatment with various concentrations of As^III alone (0.3, 1, 3, 10, 30 and 100 µM) (a), Tetra alone (2, 4, 6, 8, 10 and 12 µg/ml) (b), their combination in constant ratio (5 µM As^III + 2 µg/ml Tetra, 10 µM As^III + 4 µg/ml Tetra, 15 µM As^III + 6 µg/ml Tetra, 20 µM As^III + 8 µg/ml Tetra, 25 µM As^III + 10 µg/ml Tetra, and 30 µM As^III + 12 µg/ml Tetra) (c), or combination treatment with relatively low concentrations (5 µM As^III + 3.5 µg/ml Tetra, 10 µM As^III + 4 µg/ml Tetra, 15 µM As^III + 4.5 µg/ml Tetra) (d) for 48 h. Relative cell viability was calculated as the ratio of the absorbance at 450 nm of each treatment group against those of the corresponding untreated control group. Data are shown as the means and SD from more than three independent experiments. ^†p < 0.05 vs. each alone. As, As^III; Tetra, tetrandrine; As + Tetra, As^III + tetrandrine