An in vitro hydrogel-based model to study dormancy associated drug resistance in metastatic breast cancer spheroids

Breast cancer remains a leading cause of mortality among women, with brain metastatic breast cancer (BMBC) posing significant challenges due to poor prognosis and therapy resistance. Dormant tumor cells evade treatment, risking late relapse and highlighting the need to study dormancy-associated resistance mechanisms. We employed a biomimetic hyaluronic acid (HA) hydrogel to induce dormancy and suspension culture to promote proliferation, allowing comparison of dormant vs. proliferating BMBC spheroid responses to chemotherapy and targeted therapy. Proliferating spheroids exhibited reduced proliferation and increased apoptosis following treatment, whereas dormant spheroids showed minimal changes, indicating resistance. In proliferating spheroids, the ratio of percentage phosphorylated-ERK/p38 positive cells decreased post-treatment, indicating susceptibility, while dormant spheroids maintained dormancy-associated signaling. Transferring spheroids from HA hydrogel to suspension reversed dormancy, and restored therapy response. Additionally, p38 MAPK inhibition reactivated dormant spheroids, enhancing therapeutic sensitivity. This platform may aid in studying dormancy-associated drug resistance, potentially guiding more effective BMBC therapies.