Objective We aim to determine how cisplatin, thymoquinone (TQ), and combination regimen can affect apoptosis of cultured SK-OV-3 cells. We also want to explore the mechanism of these influences on the cells' apoptosis by Bcl-2 and Bax gene.

Method/Materials Cell Counting Kit-8 assay was used to measure the viability of cultured ovarian cancer cells. Propidium iodide with flow cytometry was used in cell cycle analysis. Thereafter, we used fluorescein isothiocyanate–stained annexin V and propidium iodide to detect the effect of cisplatin, TQ, and combination regimen on apoptosis. Real-time PCR was used to measure the Bcl-2 and Bax levels. Western blotting was used to measure on protein expression levels of Bcl-2 and Bax.

Results In Cell Counting Kit-8 assay, we found that inhibitory effect of TQ was even better than cisplatin, and combination regimen had best inhibitory effect on cell proliferation. In cell cycle analysis, we found all regimens had obvious effect to stop cell cycle in S phase. In apoptosis assay, we found that combination regimen was better to activate cell apoptosis than cisplatin alone. Combination regimen could decrease expression of Bcl-2 and increase expression of Bax more than cisplatin or TQ alone.

Conclusions Thymoquinone and cisplatin had comparable antitumoric effects on SK-OV-3 cells, and combination regimen was even better. Thymoquinone could also activate apoptosis by regulating Bcl-2 and Bax genes. These indicated potential advantage of TQ for ovarian cancer in clinical practice and suggested future clinical trials to confirm its effectiveness.