Sialomucins

Sialomucins are a diverse family of cell-surface sialoglycoproteins characterized by an extended, rod-like polypeptide backbone heavily modified with O-linked oligosaccharides and terminal sialic acid residues [8, 14]. This structure provides a strong negative charge and facilitates their role as scaffolds for carbohydrate ligands, such as Sialyl-Lewis X, which interact with selectins to regulate leukocyte trafficking and immune cell recruitment [4, 10]. Key members of this family include CD34, Podocalyxin (PODXL), CD43, and the Sialomucin Complex (MUC4), which are involved in critical biological processes such as cell-cell adhesion, signal transduction (notably via the ErbB2 receptor), and the maintenance of mucosal integrity [9, 13, 17].\n\nIn clinical pathology, sialomucins are frequently overexpressed or hypersialylated in various cancers, where they contribute to tumor progression and metastasis by masking surface antigens from immune detection and inhibiting the cytolytic activity of natural killer cells [3, 12, 15]. They are also implicated in inflammatory conditions like ulcerative colitis and chronic respiratory diseases involving mucus hypersecretion [6, 16]. Current therapeutic strategies include monoclonal antibodies against specific family members, sialyltransferase inhibitors to modulate glycosylation patterns, and enzymatic approaches using sialidases to remove sialic acids from the tumor cell surface, thereby sensitizing tumors to immunotherapy [1, 5, 15]. However, their widespread expression in normal tissues like the endothelium poses significant challenges for achieving highly selective therapeutic targeting [14, 18].

Other names

SialoglycoproteinsMucin-type glycoproteinsSialomucin-like proteinsSialomucin complexSMC

Sialomucins act as molecular scaffolds and adhesion receptors. Therapeutic agents target them by blocking selectin-mediated leukocyte rolling, disrupting the physical barrier they create to mask tumor antigens from immune cells, inhibiting oncogenic signaling pathways (such as ErbB2 activation), and reducing excessive mucus secretion in respiratory diseases.