Fig. 1. Heparin-based (HP-B) hydrogel for 3D cell culture vs. standard 2D culture in a glass-bottom dish. In this study, we demonstrate that HP-B hydrogel promotes spheroid formation in breast cancer cells and significantly alters the transcriptomic profile and phenotype of cells compared to standard culture conditions. (A) The presentation of growth factors and endogenous signals in aqueous media cannot be precisely controlled. The cells are adherent to the surface, have a flattened morphology and form a 2D monolayer. (B) Heparin-based hydrogel acts as a biomimetic tumor niche and promotes solid-phase presentation of growth factors and endogenous signals secreted by the cells, as depicted. The presence of extracellular matrix proteins encourages self-assembly into a spheroid morphology.