3D Engineering of Synthetic Tumors

Authors: 
Button, R., Virginia Tech
Conflicting data from in vitro, in vivo, and clinical studies exist regarding the magnitude of the contribution of therapeutic agents in disease treatment, particularly in the treatment of most forms of cancer for which the long-term risk of disease relapse is ~30%. Although much of our understanding on how cells divide, migrate, and die have been generated by studying cells on two-dimensional (2D) surfaces; processes such as morphogenesis, tissue remodeling, and metastasis alter the 3D organization of the microenvironment itself making it difficult, if not impossible, to recapitulate these processes in 2D culture systems. To more closely capture the conditions that cells experience in vivo, we have developed a 3D sacrificial printing system to generate biodegradable scaffolds of filament networks to grow spheroid-printed cells in a defined architectural matrix and keep them viable for long periods while allowing real-time bioluminescence recording. We aim to use this technology to provide a more realistic assessment of the impact of the cellular microenvironment and systemic factors in tumor development when adhesive, mechanical, and chemical components are taken into consideration.

Our model is a functional 3D printing system that builds scaffold structures based on a 3D sacrificial molding of carbohydrate glass. This allows the production of a network of channels, fabricated by creating a lattice of filaments, which become perfusable channels once the sugar scaffold is sacrificed. This casting is used to mimic vascular networks for perfusable-engineered 3D tumors and for growing cells encapsulated in a variety of extracellular materials (ECM). To facilitate fluid delivery in this biomimetic 3D environment, we incorporate a microsyringe pump connected to the channel inlet and an outlet channel linked to a waste reservoir to obtain a more accurate representation of the flow rate conditions found in the vasculature. With this modification, we ensure the controlled-delivery of systemic factors to the ECM under conditions that closely resemble physiological scenarios. Cancer cells are printed in an ECM of collagen in the form of co-cultured spheroids (with two or more cell types in varying ratios) as they strikingly mirror the 3D tumor heterogeneity and relevant pathophysiological gradients found in in vivo tumors. The bioprinting of spheroid-containing cells in a sacrificial 3D system allows for the incorporation of cancer stem cells or primary stem cells, the developing of core tumor necrosis, and multicellular arrangements that favor cell-cell contacts in a vascularized context.