CK20 expression in colon cancer spheroids. (A) CT320X6 (upper panel) and HT29 (lower panel) spheroids were immunostained against CK20 (yellow) and nuclei were counterstained with TOPRO-3 (cyan). Acquisitions were taken at 70 μm depth. Almost all cells were positive (scale bar = 50 μm). (B) Permeabilized cells from dissociated CT320X6 (upper panel) and HT29 (lower panel) spheroids were labelled with the same mAb against CK20. FC analysis confirmed a population with almost 100% of positive cells.