Abstract Dystroglycan is a ubiquitously expressed cell membrane receptor that mediates interactions between cells and basement membranes in various epithelia. Dystroglycan is synthesized as a preprotein that is cleaved in two peptides: the transmembranal beta-dystroglycan, and the extracellular laminin receptor alpha-dystroglycan. In many epithelium-derived cancers, beta-dystroglycan is detected but alpha-dystroglycan has been reported to be absent. Here we report that alpha-dystroglycan is correctly expressed and trafficked to the cell membrane but lack its laminin-binding capabilities as a result of the silencing of the glycosyltransferase LARGE in a cohort of highly metastatic epithelial cell lines derived from breast, cervical, and lung cancers. As a result of this glycosylation defect, alpha-dystroglycan presents a lower MW on Western blot analysis. Exogenous expression of LARGE in these cancer cells restores the normal glycosylation and laminin-binding of alpha-dystroglycan leading to enhanced cell adhesion and reduced cell migration in vitro. The relevance of alpha-dystroglycan glycosylation in breast cancer is highlighted by the loss of the functionally active form of the receptor during mammary tumor growth in the mouse model for breast cancer MMTV-Neu(YD). Our findings demonstrate that LARGE repression underlies the defective dystroglycan-mediated cell adhesion that is observed in epithelium-derived cancer cells and uncovers dystroglycan hypo-glycosylation as factor in cancer progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 996.