Abstract
Gangliosides are acidic glycosphingolipids involved in cell-adhesion, signal-transduction and tumor progression. GD3 synthase (GD3S/ST8SIA1), a key enzyme in ganglioside biosynthesis, is upregulated in many cancers, including GD2+ breast cancer stem-like cells (BCSCs) in triple-negative breast cancer (TNBC). Here, we demonstrated the immunomodulatory role of GD3S and identified a fully humanized anti-GD2 antibody, naxitamab, as a therapeutic tool to target GD3S/GD2+ breast tumors. GD3S expression correlates with immune-checkpoint activation and reduced immune infiltration. Ectopic overexpression of GD3S suppressed macrophage-mediated phagocytosis and NK or T cell-induced cell death in BC cells. Lipidomic analysis identified GD2 as the major effector ganglioside altered upon GD3S overexpression in TNBC cells. Moreover, naxitamab treatment enhanced macrophage-mediated phagocytosis and NK cell-mediated cytotoxicity and inhibited tumor growth in a TNBC patient-derived xenograft model. Our findings highlight GD3S-driven immunosuppression and provide proof-of-concept that naxitamab, with activated immune cells, reverses this effect, revealing its therapeutic potential in treating GD2+ BC.