CURCUMIN INDUCED CHANGES IN TP53 AND CYCLIN D1 ENHANCE CYTOTOXIC EFFECT OF CISPLATIN IN HUMAN OVARIAN CANCER CELLS

Abstract

Curcumin, the active ingredient of tumeric, has anti-proliferative and chemo-sensitizing properties in other cancer cells. Curcumin, through the actions of the tumor suppressor protein TP53, can arrest the cell-cycle in the G2/M phase leading to the release of cytochrome c from mitochondria causing apoptosis, or by down-regulation of cyclin D1 preventing apoptosis. The objective of this experiment was to determine effects of curcumin on cell proliferation and apoptosis in human epithelial ovarian cancer SKOV-3 cells. It was hypothesized that the anti-proliferative properties of curcumin would enhance the TP53-mediated apoptotic effect of cisplatin. Cultured SKOV-3 cells were treated with curcumin (0, 10, or 20 μM) for 4, 8, 16 and 24 h at 37°C and expression of TP53 and cyclin D1 was determined by Western blot analysis. Viability of similarly treated cells was determined by trypan blue staining. Incidence of apoptosis was detected by TUNEL assay. Effects of curcumin and cisplatin (0.25 μg/ml) on the numbers of metabolically active cells were determined by MTT assay. Data were analyzed by GLM methods of SAS. Curcumin at 10 and 20 μM decreased (P < 0.001) numbers of viable cells. Curcumin at 20 μM, but not 10 μM, increased (P < 0.001) expression of TP53. Expression of cyclin D1 was decreased (P < 0.001) with 10 and 20 μM curcumin. Although curcumin decreased numbers of viable cells, numbers of cells with positively-stained apoptotic nuclei were small < 10%. Cisplatin or curcumin at 10 or 20 μM alone decreased (P < 0.001) numbers of metabolically active cells. Numbers of cells were further decreased (P < 0.05) when cells were treated with curcumin in combination with cisplatin, when compared to curcumin or cisplatin alone. The reduced number of metabolically active cells following treatment with curcumin may be due to the arrested cell cycle mediated through an increased TP53 and decreased cyclin D1 expression. Lack of a robust apoptotic effect suggests that curcumin, while possibly lytic at high doses, at low doses may primarily arrest the cell cycle facilitating an increased cytotoxic effect of cisplatin. (poster)