Three-Dimensional <i>in Vitro</i> Models: A Promising Tool To Scale-Up Breast Cancer Research.

Common models used in breast cancer studies, including two-dimensional (2D) cultures and animal models, do not precisely model all aspects of breast tumors. These models do not well simulate the cell-cell and cell-stromal interactions required for normal tumor growth in the body and lake tumor like microenvironment. Three-dimensional (3D) cell culture models are novel approaches to studying breast cancer. They do not have the restrictions of these conventional models and are able to recapitulate the structural architecture, complexity, and specific function of breast tumors and provide similar <i>in vivo</i> responses to therapeutic regimens. These models can be a link between former traditional 2D culture and <i>in vivo</i> models and are necessary for further studies in cancer. This review attempts to summarize the most common 3D <i>in vitro</i> models used in breast cancer studies, including scaffold-free (spheroid and organoid), scaffold-based, and chip-based models, particularly focused on the basic and translational application of these 3D models in drug screening and the tumor microenvironment in breast cancer.