(84c) Engineering a Three-Dimensional Model of Vascularized Human Tumor Tissue

The increased awareness that 3D culture systems provide a more physiologically relevant environment compared to 2D monolayers has stimulated interest in creating multicellular tumor spheroids to study cancer in vitro. While there have been significant advances in “tumor engineering”, few systems are able to capture the subtlety of complex in vivo processes such as angiogenesis and neovascularization. Here, we introduce a novel 3D in vitro model of tumor angiogenesis that features cellular heterogeneity, stromal driven vessel formation, and direct cell-cell contact of cancer cells and endothelial cells. Co-cultures of endothelial colony forming cell-derived endothelial cells (ECFC-ECs) from cord blood and human epithelial-based tumor cells of breast (MDA-MB-231), colon (SW620), or lung (A549) origin were formulated into multicellular spheroids. The spheroids were then embedded in a fibrin gel distributed with a normal stromal cell (primary human lung fibroblasts). After 7 days of culture in either 20% or 5% O₂ conditions, the resulting vessel networks were imaged using confocal microscopy. The ECFC-ECs exhibited robust sprouting angiogenesis from the spheroid, and also formed a distinct and contiguous vessel network within the spheroid itself. The model was amenable to all four different cell lines, each demonstrating a characteristic influence on the resulting vessel networks. Interestingly, the model cell line SW620 also exhibited marked intravascular tumor cell migration. Individual tumor cells were tracked as they migrated within the lumens of the microvessels. Tissues cultured in 5% O₂ exhibited significantly enhanced intravascular cell migration compared to 20% O₂, consistent with epithelial to mesenchymal transition. Our results demonstrate the utility of a model system that may be used to study how different cancer cell types communicate with normal endothelial cells to direct microvessel formation, and intraluminal cell migration. This flexible and reproducible experimental platform has the potential to improve the clinical relevance of 3D in vitro culture systems by not only providing a more accurate simulation of in vivo tumor angiogenesis, but also enabling the delivery of anticancer agents via an engineered vascular network.