Heterotypic breast cancer model based on a silk fibroin scaffold to study the tumor microenvironment.

An intensive investigation of the development of in vitro models to study tumor biology has led to the generation of various three-dimensional (3D) culture methods that better mimic in vivo conditions. The tumor microenvironment (TME) is shaped by direct interactions among cancer cells, cancer-associated cells and the extracellular matrix (ECM). Recognizing the need to incorporate both tissue dimensionality and the heterogeneity of cells, we have developed a 3D breast cancer model. NIH3T3 fibroblasts and EMT6 breast cancer cell lines were seeded in various ratios onto a silk fibroin scaffold. The porosity of the silk scaffold was optimized to facilitate the growth of cancer cells. EMT6 and NIH3T3 cells were modified to express GFP and turboFP635, respectively, which enabled the direct analysis of the cell morphology and colonization of the scaffold and for the separation of the cells after their co-culture. Use of 3D mono-culture and 3D co-culture methods resulted in the modification of cell morphology and in a significant increase in ECM production. These culture methods also induced cellular changes related to EMT (epithelial-mesenchymal transition) and CAF (cancer-associated fibroblast) markers. The presented model is an easy to manufacture, well-characterized tool that can be used to study processes of the TME.