ODSEI Chip: An Open 3D Microfluidic Platform for Studying Tumor Spheroid‐Endothelial Interactions

Abstract Current in vitro models of 3D tumor spheroids within the microenvironment have emerged as promising tools for understanding tumor progression and potential drug responses. However, creating spheroids with functional vasculature remains challenging in a controlled and high‐throughput manner. Herein, a novel open 3D‐microarray platform is presented for a spheroid‐endothelium interaction (ODSEI) chip, capable of arraying more than 1000 spheroids on top of the vasculature, compartmentalized for single spheroid‐level analysis of drug resistance, and allows for the extraction of specific spheroids for further analysis. As proof of concept, the crosstalk between breast cancer spheroids and vasculature is monitored, validating the roles of endothelial cells in acquired tamoxifen resistance. Cancer spheroids exhibited reduced sensitivity to tamoxifen in the presence of vasculature. Further analysis through single‐cell RNA sequencing of extracted spheroids and protein arrays elucidated gene expression profiles and cytokines associated with acquired tamoxifen resistance, particularly involving the TNF‐α pathway via NF‐κB and mTOR signaling. By targeting the highly expressed cytokines (IL‐8, TIMP1) identified, tamoxifen resistance in cancer spheroid can be effectively reversed. In summary, the ODSEI chip allows to study spheroid and endothelial interaction in various contexts, leading to improved insights into tumor biology and therapeutic strategies.