Conditioned medium from OC cells do not suppress TRAIL-induced cell death. CaOV3 cells were challenged with TRAIL (50 ng/ml) and either fresh medium (Fresh), 5-25% SKOV3 or COV2 conditioned medium, or OPG (25 ng/ml) or ascites (10%) for 48 h, and cell viability was determined by XTT assay. Data are expressed as means of triplicates from three independent experiments ± SD. ** P < 0.001 compared to control. (B) OPG concentrations in the cell supernatant of TRAIL sensitive OC cell lines CaOV3 and OVCAR3, TRAIL resistant OC cell lines SKOV3 and COV2, and human primary ovarian tumor cells OVC215A, OVC238A, OVC285A, OVC327A and OVC346A were measured by ELISA after culture of confluent cells for 48 h.