Cytotoxicity of JS-K in WT OVCAR-8 (■-■) and in NCI/ADR-RES (R, •-•) tumor cells (Panel A). Effects of JS-K (25 nM, •-•) and (50 nM, Δ-Δ) on ADR cytotoxicity (■-■) in NCI/ADR-RES tumor cells (Panel B), and effects of JS-K on ADR cytotoxicity in WT OVCAR-8 tumor cells (Panel C) following 72 h of drug treatment. Cells were counted as described in the methods section. Values represent three separate experiments carried out in duplicates. ***, ** and * p values ≤ 0.001, 0.005, and ≤ 0.05, respectively, compared with concentration-matched samples.