Fig. 5: COX-II inhibitor celecoxib enhances TRAILR2 expression and synergizes with TRAIL treatment in eliminating cancer cell spheroids.

a Cells grown in 2D or as spheroids (day 11) were treated with 50 μM celecoxib for 72 h. TRAILR expression was determined by flow cytometry. Data are shown as mean values ± SEM from at least three independent experiments. b HCT116 spheroids (day 11) were stimulated with 50 μM celecoxib for 72 h. Paraffin-embedded slices were immunohistochemically stained for TRAILR2 and counterstained with hematoxylin. Cells were color coded according to TRAILR2 expression amounts (absent (blue), low (yellow), medium (orange) and high (red)). Images are representative of two independent experiments. Scale bars = 100 μm. c, d Spheroids of HCT116 and NCI-H460 cells (day 11) were stimulated with 50 µM celecoxib for 72 h, with TRAIL added after 48 h. The loss of viability was determined flow cytometrically by Annexin V-EGFP staining. Data show mean values ± SEM of three independent experiments. Asterisks indicate statistical significance (*p ≤ 0.05, ***p ≤ 0.001, ns not significant; Two-way ANOVA with Bonferroni correction). Data from (c) served to calculate the coefficient of drug interaction (CDI), with values < 0.7 indicating strong synergism (d). e, f Cells grown in 2D or as spheroids (day 11) were stimualted with 50 µM celecoxib for 72 h, with 0.6 nM TRAIL added after 48 h. Viability loss was determined by Annexin V-EGFP staining and flow cytometry. Data are mean values ± SEM from three independent experiments.