Cells grown as three-dimensional (3D) spheroids are thought to more closely mimic in vivo physiology in terms of morphology, structural complexity, and phenotype. Being more physiologically relevant, 3D cultures can be highly predictive for compound profiling and evaluating cytotoxicity, a critical step in evaluating chemotherapeutic drug candidates. Unfortunately, evaluation of drug cytotoxicity traditionally has relied on the use of two-dimensional (2D) cell culture monolayers. When grown in monolayers, cells are not exposed to soluble gradients, are forced into an apical-basal…