Modeling Early Metastatic Progression in Breast Cancer Using a Barrier‐Free, Perfusable Spheroid‐on‐a‐Chip Platform

ABSTRACT

Metastatic dissemination is the leading cause of cancer‐related mortality, yet the early steps in this process remain difficult to study using current experimental models. Although organ‐on‐a‐chip platforms recapitulate key features of the tumor microenvironment (TME), most fail to integrate physiologically relevant invasion, intravasation, and circulation within a single system. Membrane‐ and pillar‐based designs hinder endothelial crossing and imaging, while open‐interface approaches often lack stable perfusion and controlled positioning of 3D cell aggregates. Here, an open‐port, barrier‐free microfluidic device is presented, fabricated via surface treatment‐based patterning, for investigating early metastatic progression from a tumor spheroid. The planar device incorporates a centrally confined gel matrix accessible via a top‐loading port for precise spheroid placement, flanked by endothelialized lateral channels in direct contact with the matrix and perfusable under defined shear stress. Using MDA‐MB‐231 breast cancer spheroids, the model recapitulates key aspects of tumor cell migration, tumor‐induced endothelial disruption, and intravasation, while enabling flow‐mediated downstream recovery of viable intravasated cells. Overall, this device provides a physiologically relevant platform for the integrated, high‐resolution, and longitudinal investigation of early metastatic events, providing a foundation for future mechanistic studies and molecular characterization of metastatic cell populations.