Moreover, as the attachment of cells to an extracellular matrix (ECM) through integrin receptors modifies gene expression [20], leading to a signaling cascade involved in invasion and metastatic processes, and because integrin clustering is dependent upon small GTPases of the Rho family, we analyzed the consequences of Rac3 silencing on MDA-MB-231 cancer cell adhesion to collagen type I. Adhesion to collagen was tested under flow conditions and in the presence of blood, since hydrodynamic shear forces appear to influence the adhesion of cancer cells to the extracellular matrix. Here, RAC3 is linked to cancer.