Fig. 2. Spatial patterns of TRAILR1/R2 expression correlate with TRAIL responsiveness in tumor cell spheroids.

a Spheroid slices (day 11) were immunohistochemically stained for TRAILR1 or TRAILR2 and counterstained with hematoxylin. TRAILR staining intensity was color coded (absent (blue), low (yellow), medium (orange), and high (red)). Scale bars = 100 μm. b TRAILR expression in spheroid layers. Percentage of cells with no, low, medium, and high TRAILR expression are shown are mean values ± SEM from n = 3 spheroids. c Representative spheroid cross-sections were reconstructed based on mean spheroid metrics (spheroid diameter, cell number, TRAILR expression amounts) and color coded as in (a) and (b). d Spheroids slices (day 11) were fixed and stained for Ki67. Nuclei were stained with DAPI. Images are representative of three independent experiments. Scale bars = 100 µm. e Cells isolated from spheroids (day 11) were flow cytometrically analyzed for surface TRAILR amounts and, following permeabilization, Ki67. Scatter plots are representative of three independent experiments. R² were obtained for linear regression. Table shows Spearman’s rank correlation coefficient (ρ) rho and associated probability values.