Table I.

β-Elemene increases cisplatin cytotoxicity and enhances cisplatin sensitivity in human ovarian carcinoma cells, as determined by MTT assay.

	IC50
Drug	24 h	48 h	72 h	96 h
A2780 cells
β-Elemene (μg/ml)	65	65	65	60
Cisplatin (μM)	6.2	1.75	1.6	1.5
β-Elemene + cisplatin (μM)	3.8	0.8	0.75	0.6
Dose-modifying factor	1.6	2.2	2.1	2.5
A2780/CP70 cells
β-Elemene (μg/ml)	80	70	68	65
Cisplatin (μM)	95	66	65	60
β-Elemene + cisplatin (μM)	2.5	1.9	1.85	1.0
Dose-modifying factor	38	34.7	35.1	60

The results reveal that β-elemene increased cisplatin cytotoxicity by 34.7- to 60-fold in A2780/CP70 cells, but only 1.6- to 2.5-fold in A2780 cells. The IC₅₀ (half maximal inhibitory concentration) value is defined as the concentration of β-elemene or cisplatin needed for 50% inhibition of cell growth and proliferation. The dose-modifying factor (DMF) was calculated as the IC₅₀ for cisplatin without β-elemene divided by the IC₅₀ for cisplatin with β-elemene: DMF = IC₅₀ (cisplatin) ÷ IC₅₀ (cisplatin + β-elemene). MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.