Cisplatin-mediated sensitivity to TRAIL-induced cell death in human granulosa tumor cells

Abstract

Objectives: The goal of the present study was to determine the efficacy of combinatorial treatment using cisplatin and tumor necrosis factor-related apoptosis including ligand (TRAIL) to promote apoptosis in granulosa cell tumor (GCT) lines, in vitro.

Methods: Two human GCT lines (COV434 and KGN) were treated with cisplatin or TRAIL, alone or in combination. The cytotoxic effects of each treatment were evaluated using a methyl tetrazolium salt (MTS) assay. Initiation of TRAIL-induced apoptosis was verified by PARP- and FLIP-cleavage. Overexpression and knockdown studies were conducted to evaluate the role of p53 in TRAIL-induced cell death. Real-time PCR was used for gene expression analysis of the TRAIL receptor dr5 and the pro-apoptotic bax following treatment with cisplatin.

Results: Treatment with TRAIL (100-200 ng/ml) led to a slight, but significant, loss of cell viability following an 18-h culture. This effect was enhanced following pre-treatment with cisplatin (25 microM) for 2 or 18 h. Moreover, pre-treatment with cisplatin decreased the maximal effective dose of TRAIL from 100 ng/ml to as low as 3 ng/ml in both cell lines. GCT lines overexpressing or deficient in p53 were used to determine the requirement for p53 on TRAIL-induced apoptosis. While the level of p53 expression enhanced both the death-inducing and TRAIL-sensitizing effects of cisplatin, TRAIL-induced cell death was found to occur independent of p53.

Conclusions: These data suggest that the efficacy of cisplatin in GCT cells can be enhanced through combinatorial treatment with TRAIL. This result is due to both p53-dependent (cisplatin) and -independent (TRAIL) mechanisms. Combinatorial treatment of GCTs with cisplatin and TRAIL may provide an efficacious addition to cisplatin-based regimens.