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. 2018 Feb 12;9(18):14228–14250. doi: 10.18632/oncotarget.24479

Figure 4. TRAIL induces apoptosis in NPC cells.

Figure 4

Figure 4

Figure 4

Figure 4

Figure 4

Figure 4

Figure 4

(A) Surface expression of TRAIL-R1, TRAIL-R2 and FAS in NPC cells. TRAIL-R2 is expressed in all NPC cell lines but not nasoepithelial cells; low expression in cell line C-666-1 and C17-PDX cells; no expression of TRAIL-R1 in NPC cell lines but nasoepithelial cells. No expression of FAS except in nasopepithelial cells and low in NPC cell line C666-1 and C17-PDX cells. Data were acquired by flow cytometry and were compared to specific isotype controls. (B) Induction of apoptosis via TRAIL in NPC cell lines but not nasopepithelial cells. Cells were exposed to TRAIL (0.1 μg/ml) or FAS Ligand (0.1 μg/ml) for 24 h. The percentage of apoptotic cells was determined by flow cytometry of cells with subG1-content. Quantitative data are reported as means ± S.E.M. (triplicate samples). *p < 0.05; **p < 0.01; ***p < 0.001. (C) Immunofluorescence for active caspase-3. Treatment with TRAIL (0.1 μg/ml) for 24 h induced the expression of active caspase-3 in five out of six NPC cell lines. No induction of active caspase-3 was observed when NPC cells were incubated with FAS Ligand. Active caspase-3 was examined under a fluorescence microscope at 200× magnification. (D) Immunohistochemistry for TRAIL-R1, TRAIL-R2 and TRAIL in an NPC tumor. NPC cells (⋆) stained by cytokeratin, show partially a low to moderate, predominantely membranous, less cytoplasmic expression of TRAIL-R2 and no expression of TRAIL-R1 or TRAIL; a subpopulation of tumor-infiltrating lymphocytes (T), in part stained by CD8, express TRAIL. All images at 400× magnification. Representative images of one NPC tumor are shown; similar staining patterns were obtained in NPC tumors of two other patients analyzed. (E) Surface expression of TRAIL-R2 after incubation of cells with IFNβ. Cells were incubated for 72 h with (gray area) or without (white area) 1,000 U/ml IFNβ and then stained and analyzed as in (A). IFNβ upregulated TRAIL-R2 expression in NPC cell lines HONE, HONE-EBV, TW01 as well as C17-PDX cells but not in C666-1 cells and nasoepithelial cells.