Subsequent Metastasis via Regulation of In Vivo Tumor Cell Motility by the Tetraspanin CD151

travasation, which ultimately result in the colonization of a sec-ondary site (Bockhorn et al., 2007; Pantel and Brakenhoff, 2004; Bernards and Weinberg, 2002). Throughout the journey from its original location on route to a distant site, themetastasiz-ing tumor cell interacts with its changing microenvironment. To-gether with transmembrane signaling receptors, adhesion com-plexes on the cell surface convey signals from the instructive microenvironment and regulate tumor cell behavior. The ability of the tumor cell to mobilize itself and leave the original tumor site is one of the prerequisite requirements of tumor cell dissem-cates the need for a functional migration machinery. Cellular migration is mediated by the adhesion receptors (integrins), which regulate cellular behavior through cytoplasmic signaling pathways including Rho GTPases and kinases (Felding-Haber-mann et al., 2001; Guo and Giancotti, 2004). Adhesion receptor function is tightly controlled through regulatory pathways that in-clude integrin-associated transmembrane proteins such a