Aberrant O-glycosylation characterized by N-acetylgalactosamine (GalNAc) attachment to serine or threonine residues leads to accumulation of the tumor-associated Tn antigen in colorectal cancer (CRC), contributing to immune evasion and therapeutic resistance. Here, we develop a homocysteine-crosslinked zwitterionic nanocomplex for targeted delivery of small interfering RNA (siRNA) against N-acetylgalactosaminyltransferase 1 (GalNT1), a key glycosyltransferase initiating Tn antigen biosynthesis. Zwitterionic surface modification enhances tumor accumulation and facilitates intracellular siGalNT1 delivery via caveolin-mediated endocytosis. siRNA-mediated GalNT1 silencing markedly reduces Tn antigen expression in CRC cells. Concurrently, elevated hydrogen sulfide level in the tumor microenvironment triggers disulfide bond cleavage in the nanocomplex, exposing homocysteine residues. These residues then react with intracellular serine through cystathionine β-synthase (CBS)-mediated catalysis, thereby depleting serine and further suppressing Tn antigen biosynthesis. This dual intervention disrupts the immunosuppressive Tn-macrophage galactose-type lectin (MGL) axis, provokes antitumor immunity, inhibits tumor growth and metastasis in CRC models. Our findings highlight a synergistic nanoplatform targeting both glycosylation and metabolic vulnerabilities, offering a promising strategy for CRC glyco-immunotherapy.
Keywords: Colorectal cancer; Aberrant O-glycosylation; siRNA delivery; Tn antigen; Glyco-immunotherapy
