Breast cancer immunotherapy: current biomarkers and the potential of in vitro assays.

Breakthroughs in metastatic breast cancer care require new model systems that can identify the unique features and vulnerabilities of each cancer. Primary tumor cultures are proposed to efficiently screen multiple treatment options in a patient-specific strategy to maximize therapeutic benefit, minimize toxicity, and enable mechanistic insights that inspire future biomarkers for patient selection. To realize the potential of patient-specific cultures, new tools are needed to capture cell-by-cell variability in behavior and dynamic response to treatments in living 3D specimens. Potential bioengineering tools that can achieve this include optical microscopy to image single-cell dynamics and microphysiological in vitro systems to evaluate cell-cell interactions and immunotherapies.