Abstract

Collective migration of polyclonal tumor cell clusters is a key driver of efficient cancer metastasis, yet how microscale mechanical heterogeneity within the extracellular matrix (ECM) governs this process remains largely unclear. Here, we report a cellulose nanofibrous hydrogel (CFB) that recapitulates the irregular fibrotic architecture of malignant ECM and captures its cell-scale mechanical heterogeneity. In contrast to the largely static and monoclonal behavior observed in conventional homogeneous synthetic hydrogels and commercial basement membrane extract, CFB exhibits up to 16-fold local stiffness variations and rapidly induces tumor cell aggregation into polyclonal clusters. These clusters subsequently undergo leader cell-guided collective migration, and the migration capacity directly correlates with metastatic potential, serving as a functional predictor. Mechanistically, we demonstrate that localized mechanical differences activate Piezo1-mediated mechanotransduction, thereby driving both the initiation and progression of cell aggregation and collective migration. CFB-derived tumor clusters exhibit multiple metastatic hallmarks and pronounced chemoresistance, and in vivo experiments further confirm their enhanced metastatic potential. Overall, our findings reveal how ECM mechanical landscapes drive tumor cluster formation and invasion, and support the use of CFB as a controllable engineered platform for investigating metastasis-associated tumor behaviors and therapeutic strategy development. STATEMENT OF SIGNIFICANCE: Efficient cancer metastasis is often accompanied by the formation of polyclonal tumor cell clusters and their collective migration, yet how microscale mechanical heterogeneity within the ECM governs this process remains largely unclear.