Comparison of U-87 MG spheroids grown on ultra-low attachment (ULA) plates or agar: immunostaining. Hematoxylin and eosin (H&E), glucose transporter 1 (GLUT-1) or Ki67 antibody staining of sections of U-87 MG spheroids grown for 4, 7 and 14 days on (a) ULA 96-well round-bottomed plates or (b) agar-coated 96-well flat-bottomed plates. Spheroids on (a) ULA plates show a tighter structure than spheroids grown on (b) agar, across all timepoints. H&E staining is homogeneous, while there was a gradient of proliferation (Ki67) in larger spheroids (day 14). A more intense staining of GLUT-1 was observed concomitantly with the age of the spheroids, irrespective of the means of generation (a, b). Scale bar 100: μm.