Mechanically-tuned alginate gels as new 3D breast cancer models

Three-dimensional (3D) cell cultures represent fundamental tools for the comprehension of cellular phenomena both in normal and pathological conditions. In particular, mechanical stimuli not less than chemical ones have a relevant role on cell fate, cancer onset and malignant progression. Here, we realize mechanically tuned alginate hydrogels for studying the role of substrate elasticity on breast adenocarcinoma cells activity. Hydrogels Elastic Modulus (E) was measured via Atomic Force Microscopy and a remarkable range (20–4000 kPa) was obtained. A breast cancer cell line, MCF-7, was seeded within the 3D gels, on standard Petri and alginate-coated dishes (2D controls). Cells showed dramatic morphological differences when cultured in 3D vs. 2D, exhibiting a flat shape morphology in both 2D conditions, while they maintained within gels a circular, clusterorganized conformation similar to the in vivo one. In 3D culture, we observed a strict correlation between cells viability and substrate elasticity; in particular, MCF-7s constantly decreased in number with increasing hydrogel elasticity. The highest cellular proliferation rate, associated to a formation of cell clusters, occurred in two weeks of culture only within the softest hydrogels (E=20-40 kPa), highlighting the need of adopting more realistic and a priori defined models for in vitro cancer studies.