Breast cancer has been one of the biggest killers of women due to its susceptibility and high metastasis. Pathological observations show that malignant cancer cells frequently invade the surrounding normal tissue in collective rather than individual cell migration. For individual cell migration, it has been found that the Rho/ROCK signaling is upregulated and correlates with disease progression. Meanwhile, Rho activates myosin-II and the actomyosin-mediated contraction creates tension within the cells. However, the roles of the activation of the Rho/ROCK signal pathway in collective cell migration and the precise mechanisms by which myosin-II fine-tunes the contractility of the cells to allow for the reorganization of the cytoskeleton that drives collective cell migration, remain unclear. This study investigated whether the high cellular contractility could activate the inside-out signal trans-ductions and how did the intracellular force contribute to the collective cell migration.