Matriglycan on α-dystroglycan (αDG), a glycan specifically expressed on the cell surface, plays critical roles in various biological functions by regulating its chain length. Abnormal expression of matriglycan is a known cause of congenital muscular dystrophy. Structurally, matriglycan consists of a phosphorylated trisaccharide (ManP-GlcNAc-GalNAc) extended by two ribitol phosphate (RboP) units, followed by repeating disaccharide units of xylose and glucuronic acid (Fig. 99.1). Notably, matriglycan shortening has been reported in cancer cells and tissues. In colorectal cancer, for instance, capping of the glycan by glycerol phosphate (GroP) inhibits elongation, thereby enhancing cell motility (Fig. 99.1) [1, 2]. GroP-modified, shortened matriglycan is frequently observed in stage IV tumors with high metastatic potential [2]. These findings suggest that matriglycan shortening contributes to a tumor-promoting microenvironment.