Effect of PPARγ ligands on Dex-resistant MM cells. (A) Expression of PPARγ on MM1S and MM.1R cell lines detected by Western blot. (B,C) Dose-dependent inhibition of PPARγ ligands on cell growth of both MM.1S and MM.1R cells. Proliferation of quiescent MM.1R (B) or MM.1S cells (C) in culture was examined following treatment with 10 ng/M IL-6 and increasing concentrations (abscissa) of 15-d-PGJ2 (○), troglitazone (□), or dexamethasone (▵) for 16 hours at 37°C. [³H]-thymidine incorporation was analyzed. (D) Effects of PPARγ ligands on drug-resistant MM cell–induced IL-6 release from stromal cells. HS-5 cells were cocultured with MM.1S or MM.1R cells and treated with 1 μM 15-d-PGJ2 or 10 μM troglitazone for 48 hours. IL-6 concentration was determined in supernatants. Error bars represent the mean (± SE) from 3 independent experiments.