Development of TRACER: tissue roll for analysis of cellular environment and response

The tumour microenvironment is heterogeneous and consists of multiple cell types, variable extracellular matrix (ECM) composition, and contains cell-defined gradients of small molecules, oxygen, nutrients and waste. Emerging in vitro cell culture systems that attempt to replicate these features often fail to incorporate design strategies to facilitate efficient data collection and stratification. The tissue roll for analysis of cellular environment and response (TRACER) is a novel strategy to assemble layered, three-dimensional tumours with cell-defined, graded heterogeneous microenvironments that also facilitates cellular separation and stratification of data from different cell populations from specific microenvironments. Here we describe the materials selection and development of TRACER. We find that cellulose fibre scaffolding is an ideal support to generate tissue constructs having homogenous cell seeding and consistent properties. We explore ECM remodeling and long-term cell growth in the scaffold, and characterize the tumour microenvironment in assembled TRACERs using multiple established analysis methods. Finally, we confirm that TRACERs replicate small molecule gradients of glucose and lactate, and explore cell phenotype associated with these gradients using confocal microscopy, flow cytometry, and quantitative PCR analysis. We envision this technology will provide a platform to create complex, yet controlled tumour microenvironments that can be easily disassembled for snapshot analysis of cell phenotype and response to therapy in relation to microenvironment properties.