The Role of Glycan Structures in Modulating GM-CSF Bioactivity: Insights from Glycoengineering.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein cytokine with therapeutic potential in cancer and neutropenia treatment. While glycosylation of GM-CSF reduces immunogenicity and enhances serum bioavailability, it can also diminish receptor binding and bioactivity. Based on transcriptomic analysis of human T lymphocytes reported previously, GM-CSF-producing cells exhibit elevated expression of Alpha-1,6-Mannosylglycoprotein 6-Beta-N-Acetylglucosaminyltransferase (MGAT5), which encodes N-acetylglucosaminyltransferase V, an enzyme involved in N-glycan branching. Given this role of MGAT5 in glycosylation, we produced GM-CSF variants using glycoengineered Chinese hamster ovary cells to generate diverse glycoforms and assessed their bioactivity. Testing their activity on TF-1 cell proliferation, we found that decreases in GM-CSF N-glycan branching significantly suppressed its activity. These findings underscore the importance of glycosylation in modulating the efficacy and safety of GM-CSF-based therapeutics, suggesting that precise glycoengineering may be key to optimizing GM-CSF performance in clinical applications.