BT20 and MCF7 spheroids are more resistant to TRAIL-mediated apoptosis.

Flow cytometry Annexin-V/Propidium Iodide scatterplots of untreated and 200 ng/mL of TRAIL treated (A) BT20 and (B) MCF7 cells cultured as 3D spheroids and 2D monolayer 24 h after treatment conditions. Cells can be classified into four groups based on dye uptake: viable cells (lower left quadrant), early apoptotic cells (lower right quadrant), late apoptotic cells (upper right quadrant) and necrotic cells (upper left quadrant). Bright field images of untreated and 200 ng/mL TRAIL treated (C) BT20 and (D) MCF7 cells from spheroid and monolayer culture after 24 h after treatment conditions.