Identification of functional biomarkers for personalized nanomedicine in advanced breast cancer in vitro models

Nanomedicines represent promising advanced therapeutics for the enhanced treatment of breast cancer, the primary cause of cancer-related deaths in women; however, the clinical translation of nanomedicines remains challenging. Advanced in vitro models of breast cancer may improve preclinical evaluations and the identification of biomarkers that aid the stratification of patients who would benefit from a given nanomedicine. In this study, we first developed a matrix-embedded breast cancer cell spheroid model representing the extracellular matrix and confirmed the faithful recapitulation of disease aggressiveness in vitro. We then characterized factors influencing nanomedicine drug release (i.e., cathepsin B levels/activity, reactive oxygen species levels, glutathione levels, and cytoplasmic pH values) and evaluated nanomedicine internalization and cytotoxicity evaluation in our spheroid model. We confirmed the reduced-to-oxidized glutathione ratio as a functional biomarker of disulfide linker-containing polypeptide-drug conjugate effectiveness. We then established a biobank of patient-derived breast cancer organoids that recapitulate clinical intra-tumor and inter-tumor heterogeneity as a more advanced model. Analysis in organoids revealed that patient-specific responses to a polypeptide-based nanomedicine correlated with cathepsin B levels, supporting the potential of the functional biomarker for patient-tailored nanomedicine selection. Our findings highlight that exhaustively characterized advanced in vitro models support the evaluation of nanomedicines and the identification of functional biomarkers.