Engineering Mesoscopic 3D Tumor Models with a Self‐Organizing Vascularized Matrix

Abstract Advanced in vitro systems such as multicellular spheroids and lab‐on‐a‐chip devices have been developed, but often fall short in reproducing the tissue scale and self‐organization of human diseases. A bioprinted artificial tumor model is introduced with endothelial and stromal cells self‐organizing into perfusable and functional vascular structures. This model uses 3D hydrogel matrices to embed multicellular tumor spheroids, allowing them to grow to mesoscopic scales and to interact with endothelial cells. It is shown that angiogenic multicellular tumor spheroids promote the growth of a vascular network, which in turn further enhances the growth of cocultivated tumor spheroids. The self‐developed vascular structure infiltrates the tumor spheroids, forms functional connections with the bioprinted endothelium, and can be perfused by erythrocytes and polystyrene microspheres. Moreover, cancer cells migrate spontaneously from the tumor spheroid through the self‐assembled vascular network into the fluid flow. Additionally, tumor type specific characteristics of desmoplasia, angiogenesis, and metastatic propensity are preserved between patient‐derived samples and tumors derived from this same material growing in the bioreactors. Overall, this modular approach opens up new avenues for studying tumor pathophysiology and cellular interactions in vitro, providing a platform for advanced drug testing while reducing the need for in vivo experimentation.