FIG. 3.

GR isoforms differentially induced apoptosis in U-2 OS cells. (A) When treated with vehicle or DEX (100 nM) for 48 h, nucleus staining showed chromatin condensation in DEX-treated cells containing GR. (B) Flow cytometric analysis of PI labeling showed that a high percentage of cells expressing the GR-C isoforms were PI positive, whereas the GR-D-expressing cells were relatively resistant to DEX killing. Time course experiments showed that GR-C isoform-expressing cells had an earlier onset of cell death than cells expressing other GR isoforms, and GR-D isoform-expressing cells had less cell death than cells expressing the other GR isoforms after 48 h of DEX treatment. (C) Annexin V labeling showed that GR-C-expressing cells, when treated with DEX, had a greater number of cells positive for cell surface annexin V and negative for PI. Similar patterns were also observed for the PARP level (D), DNA degradation (E), and caspase activation (F). Average results from five to six experiments are presented in the bar graph. One-way ANOVA was performed to compare values from DEX-treated cells expressing different GR isoforms, which was followed by Tukey post hoc analysis. *, significantly higher than that of GRα (P < 0.05); **, significantly lower than that of GRα (P < 0.05).