Traction forces concentrate at edge protrusions in mesenchymal clusters and redistribute toward cell–cell contacts in epithelial-like clusters during SDF1 chemotaxis. (A) TFM showing substrate displacement maps in mesenchymal and epithelial-like NC clusters during chemotaxis. Zooms highlight edge protrusions and cell–cell contact regions. (B and C) Quantification of normalized traction force at edge protrusions and cell–cell contact in NC clusters shown in mesenchymal and (C) epithelial-like (n = 6). Each dot represents one cluster. Data are from at least three independent experiments. Error bars show mean ± SEM. Error bars show mean ± SEM. Statistical analysis was performed using an unpaired two-tailed Student’s t test. ****P ≤ 0.0001; *P ≤ 0.05. Scale bars: 100 µm. (D) Model summarizing the distinct strategies of collective chemotaxis. In mesenchymal clusters, traction is generated primarily at the leading edge, driven by supracellular actomyosin cables and polarized protrusions, and cell–cell cohesion is maintained by N-cadherin–mediated adhesion. In epithelial-like clusters, traction redistributes toward junctional regions, where E-cadherin adhesion and actomyosin coupling coordinate collective movement. Orange represents Rac1 activity.