The MEMIC: An ex vivo system to model the complexity of the tumor microenvironment

There is an urgent need for accurate, scalable, and cost-efficient models of the complexity and heterogeneity of the tumor microenvironment. Here, we detail how to fabricate and use the Metabolic Microenvironment Chamber (MEMIC) -- a 3D-printed ex vivo model of intratumoral heterogeneity. A major driver of the cellular and molecular diversity in tumors is the accessibility to the blood stream that provides key resources such as oxygen and nutrients. While some tumor cells have direct access to these resources, many others must survive under progressively more ischemic environments as they reside further from the vasculature. The MEMIC is designed to simulate the differential access to nutrients and allows co-culturing different cell types, such as tumor and immune cells. This system is optimized for live imaging and other microscopy-based approaches and it is a powerful tool to study tumor features such as the effect of nutrient scarcity on tumor-stroma interactions. Due to its adaptable design and full experimental control, the MEMIC can provide novel insights into the tumor microenvironment that would be difficult to obtain via other methods. As a proof of principle, we show that cells can sense gradual changes in metabolite concentration, and tune intracellular cell signaling to form multicellular spatial patterns of cell proliferation. We also show that ischemic macrophages reduce epithelial features in neighboring tumor cells highlighting the power of this system to study cell-cell interactions and non-cell autonomous effects of the metabolic microenvironment. We propose that the MEMIC can be easily adapted to study early development, ischemic stroke, and other systems where multiple cell types interact within heterogeneous environments.