Three-dimensional (3D) in vitro culture models better recapitulate the tissue microenvironment, and therefore may provide a better platform to evaluate therapeutic effects on adhesive cell-cell interactions. The objective of this study was to determine if AD-01, a peptide derivative of FK506-binding protein like that is reported to bind to the adhesion receptor CD44, would induce a greater reduction in breast epithelial spheroid adhesion to endothelial tube-like networks in our 3D coculture model system compared to two-dimensional (2D) culture. MCF10A, MCF10A-NeuN, MDA-MB-231, and MCF7 breast epithelial cells were pretreated with AD-01 either as single cells or as spheroids. Breast epithelial cell adhesion to 2D tissue culture substrates was first measured, followed by spheroid formation (breast cell-cell adhesion) and spheroid adhesion to Matrigel or endothelial networks. Finally, CD44 expression was quantified in breast epithelial cells in 2D and 3D culture. Our results show that AD-01 had the largest effect on spheroid formation, specifically in breast cancer cell lines. AD-01 also inhibited breast cancer spheroid adhesion to and migration along endothelial networks. The different breast epithelial cell lines expressed more CD44 when cultured as 3D spheroids, but this did not universally translate into higher protein levels. This study shows that 3D coculture models can enable unique insights into cell adhesion, migration, and cell-cell interactions, thereby enhancing understanding of basic biological mechanisms. Furthermore, such 3D coculture systems may also represent a more relevant testing platform for understanding the mechanism-of-action of new therapeutic agents. Impact Statement Cell adhesion is inherently different in two dimensional (2D) compared to three dimensional (3D) culture; yet, most adhesion assays in academia and industry are still conducted in 2D because few simple, yet effective, adhesion models exist in 3D. Recently we developed a 3D in vitro coculture model to examine breast epithelial spheroid interactions with endothelial tubes. We now show that this 3D coculture model can effectively be used to interrogate and quantify drug-induced differences in breast epithelial cell adhesion that are unique to 3D cocultures. This 3D coculture adhesion model can furthermore be modified for use with other cell types to better predict drug effects on cell-vasculature adhesion.
Keywords: 3D culture models; CD44; breast spheroids; cell adhesion; endothelial cells.