Tumor Spheroids Layered in an Imageable Cancer Environment (T-SLICE): a novel in vitro platform to study tumor biology

Cancer treatment is shifting away from traditional to precise therapeutic approaches informed by patient and tumor profiles. To achieve better outcomes for cancer patients, it will be necessary to design and test therapies that target the heterogeneity of tumors that exists within and between patients and even within the same tumor. Existing in vitro model systems do not fully recapitulate the physio-chemical gradients of tumors and may fall short of representing a living organism. Mouse models remain the gold standard for preclinical testing but lack the throughput needed to quickly understand mechanisms and iterate quickly to maximize therapeutic efficacy. Microfluidic systems can fill this gap but remain out of reach for most biologic laboratories due to their complexity in assembly and use. We created T-SLICE (Tumor Spheroids Layered in an Imageable Cancer Environment) to enable high-throughput imageable studies within a complex simulated tumor microenvironment (TME). Tumor spheroids are seeded on a monolayer of fibroblasts and cultured between two parallel, closely spaced glass coverslips (300-700 μm). The restrictive gap distance limits permeation of nutrients and oxygen to create gradients that recapitulate those observed in the in vivo TME. In T-SLICE, physio-chemical gradients are defined by cellular metabolism, akin to an actual tumor. We demonstrate that this is associated with changes in cellular viability, mitochondrial trans-membrane potential, and proliferation. T-SLICE provides a live-cell imaging compatible, high throughput platform that allows real-time monitoring of cellular phenotypes, function, and sociology within a cell-driven TME physio-chemistry amenable to therapeutic optimization, screening, and patient avatar modelling. ### Competing Interest Statement The authors have declared no competing interest.