NADPH oxidase 1 (Nox1) is expressed mainly in colon epithelial cells and produces superoxide ions as a primary function. We showed that Nox1 knockdown inhibits directional persistence of migration on collagen I. This paper dissects the mechanism by which Nox1 affects the direction of colonic epithelial cell migration in a two-dimensional model. Transient activation of Nox1 during cell spreading on collagen 1 temporarily inactivated RhoA and led to efficient exportation of ␣21 integrin to the cell surface, which supported persistent directed migration. Nox1 knockdown led to a loss of directional migration which takes place through a RhoA-dependent ␣2/␣3 integrin switch. Transient RhoA overactivation upon Nox1 inhibition led to transient cytoskeletal reorganization and increased cell-matrix contact associated with a stable increase in ␣3 integrin cell surface expression. Blocking of ␣3 integrin completely reversed the loss of directional persistence of migration. In this model, Nox1 would represent a switch between random and directional migration through RhoA-dependent integrin cell surface expression modulation.The two well-recognized defining hallmarks of cancer are uncontrolled proliferation and invasion (14). The conversion of a static primary tumor into an invasive disseminating metastasis involves an enhanced migratory ability of the tumor cells. Tumor cells use migration mechanisms that are similar, if not identical, to those that occur in normal cells during physiological processes such as embryonic morphogenesis, wound healing, and immune-cell trafficking (10). To migrate, cells must acquire a spatial asymmetry that enables them to turn intracellularly generated forces into net cell body translocation. Dynamic assembly and disassembly of integrin-mediated adhesion and cytoskeletal reorganization are necessary for efficient migration (29). Integrins are heterodimeric integral membrane proteins composed of an ␣ chain and a  chain. Depending on the cell type and extracellular matrix (ECM) substrate, focal contact assembly and migration can be regulated by different integrins. Collagen receptors include ␣11, ␣21, and ␣31 integrins. ␣11 and ␣31 integrins also bind laminin and have less affinity for collagen than does integrin ␣21 (47). The intrinsic propensity of cells to continue migrating in the same direction without turning is closely related to integrin/cytoskeletal interaction, which is known to regulate tractional forces, resulting in modulation of the speed and direction of cell migration (33). Interestingly, different integrin-ECM associations might have opposite effects on the regulation of the directionality of migration. Danen et al. have shown that adhesion to fibronectin by ␣v3 promotes persistent migration through activation of the actin-severing protein cofilin, which results in a polarized phenotype with a single broad lamellipod at the leading edge. In contrast, adhesion to fibronectin by ␣51 instead leads to phosphorylation/inactivation of cofilin and these cells fail to polari...