FIGURE 7.

Cryptotanshinone sensitizes TRAIL-resistant lung cancer cells. A, TRAIL-resistant A549 lung cancer cells were treated as indicated with TRAIL alone or pretreated with 20 μm CT for 12 h, washed with PBS, and then treated with TRAIL for an additional 24 h. Cell viability was assessed by the MTT assay. *, p < 0.05 versus control, CT, and TRAIL. B, crystal violet staining of A549 cells treated with CT and TRAIL as described under “Experimental Procedures.” C, A549 cells were treated with 20 μm CT for 12 h. Whole-cell extracts were analyzed for expression of DR5 and DR4 by Western blotting. D, the cell surface expression levels of DR5 in A549 cells treated with 20 μm CT for 12 h were measured by flow cytometry analysis using phycoerythrin (PE)-conjugated DR5 and isotype control antibodies. MFI, mean fluorescence intensity. E, A549 cells were treated as described above. Cells were fixed and stained with DAPI. Nuclei morphological change was visualized using fluorescence microscopy (×400). F, Western blotting of lysates from A549 cells pretreated with 20 μm CT for 12 h followed by treatment with TRAIL for 3 h using the indicated antibodies. G, normal lung MRC-9 fibroblast cells were treated as indicated with TRAIL alone or pretreated with 20 μm CT for 12 h, washed with PBS, and then treated with TRAIL for an additional 24 h. Cell viability was assessed by the MTT assay.