Csk-binding protein (Cbp),also named phosphoprotein associated with GEMs(PAG),is a ubiquitously expressed transmembrane adaptor protein which is localized in a special cytoplasmic membrane domain,called glycosphinglipid enriched microdomains or lipid rafts.Multiple tyrosines located in the cytoplasmic region of Cbp can be phosphorylated by Src family kinases (SFKs).The phosphorylated Cbp binds to and activates C-terminal Src kinase (Csk),an essential negative regulator for SFKs,leading to the down-regulation of SFK activities.Recently,we have reported that Cbp regulates EGF-signaling induced cell transformation through controlling SFK activities in NIH3T3 cells,whereby Cbp was implicated to be involved in carcinogenesis.However,functional significance of Cbp in development of cancers in vivo remains unknown.