3D bioprinting innovations: a new frontier in breast cancer research.

Breast cancer (BC) is a widely recognized second most frequent female cancer globally that is histologically and molecularly heterogeneous. Nevertheless, despite intensive studies, currently available preclinical models, particularly animal models, are of limited use for clinical applications, and thus, anticancer drug failure in clinical trials is relatively high. This gap indicates the necessity for more physiologically relevant models. Conventional two-dimensional (2D) culture models are incapable of accurately simulating the complex tumor microenvironment. However, three-dimensional (3D) cell culture and bioprinting technologies offer better options by more accurately resembling the tissue structure of original tissues and cellular activities. 3D bioprinting is capable of precise deposition of living cells and extracellular matrix (ECM) components into a predefined structure, which subsequently enables the generation of breast cancer tissue (BCT) models that closely simulate in vivo conditions. This review examines the limitations of current models, explores the potential of 3D bioprinting in developing functional and dynamic BC models, and evaluates bioinks, printing strategies, and metastatic models. We conclude by addressing the existing challenges and future directions for advancing 3D bioprinting applications.