Nanotopographic ridges align epithelial sheet migration and preserve local clonal mixing

Surface nanotopography can steer epithelial cell motion, but its effect on segregation of mixed clones is unclear. To test whether nanoridges that guide cell movement also cause segregation, we mixed nontumorigenic epithelial, MCF 10A, and their isogenic, metastatic MCF10A-PTEN-/-KrasG12V (KP) cells. Live imaging and quantitative tracking showed that the nanoridges increased speed and aligned cell trajectories with the ridge axis, with the strongest effect at the sheet front. KP cells became more elongated on ridges compared to the MCF10A. In mixtures, motility differences seen in single-type cultures were reduced, indicating coordinated motion. However, ridge guidance did not change spatial mixing: neighbor statistics and a mixing index matched flat controls, with weak cell-type-specific sorting. We conclude that nanotopographic ridges align and accelerate collective migration but do not induce clonal segregation in dense cell sheets, where cell-cell interactions dominate spatial organization. We are now exploring how microenvironmental cues modulate the short-term and long-term responses of epithelial mixtures to radiation therapy (conventional and eFLASH), bridging in-vitro collective-migration models with potentially clinically relevant FLASH effects.