Three-dimensional culture models to study drug resistance in breast cancer.

Despite recent advances in breast cancer treatment, drug resistance frequently presents as a challenge, contributing to a higher risk of relapse and decreased overall survival rate. It is now generally recognized that the extracellular matrix and cellular heterogeneity of the tumor microenvironment influences the cancer cells' ultimate fate. Therefore, strategies employed to examine mechanisms of drug resistance must take microenvironmental influences, as well as genetic mutations, into account. This review discusses three-dimensional (3D) in vitro model systems which incorporate microenvironmental influences to study mechanisms of drug resistance in breast cancer. These bioengineered models include spheroid-based models, biomaterial-based models such as polymeric scaffolds and hydrogels, and microfluidic chip-based models. The advantages of these model systems over traditionally studied two-dimensional tissue culture polystyrene are examined. Additionally, the applicability of such 3D models for studying the impact of tumor microenvironment signals on drug response and/or resistance is discussed. Finally, the potential of such models for use in the development of strategies to combat drug resistance and determine the most promising treatment regimen is explored.