In migrating tumor cells, programmed death ligand 1 (PD-L1) activates RhoA by localizing integrin β4 at the rear of the cell and binding to the actin at the rear, promoting RhoA-mediated contractility and maintaining lower membrane tension at the rear, thereby regulating cell polarity and sustaining the continuous migration of tumor cells (132, 133). The gene discussed is RHOA; the disease is neoplasm.