α2,6-Sialylation promotes immune escape in hepatocarcinoma cells by regulating T cell functions and CD147/MMP signaling.

Altered glycosylation is a common feature of cancer cells and plays an important role in tumor progression. β-Galactoside α2-6-sialyltransferase 1 (ST6Gal-I) is the critical sialyltransferase responsible for the addition of α2-6-sialic acid to the terminal N-glycans on the cell surface. However, the functions and mechanism of ST6Gal-I in tumor immune escape remain poorly understood. Here, we found that ST6Gal-I overexpression promoted hepatocarcinoma cell proliferation, migration, and immune escape by increasing the levels of CD147, MMP9, MMP2, and MMP7. When CD8+ T cells were co-cultured with cell lines expressing different levels of ST6Gal-I, we found that ST6Gal-I upregulation inhibited the T cell proliferation and increased the secretion of IL-10 and TGF-β1, while secretion of IFN-γ and TNF-α was diminished. In a syngeneic tumor transplant model, ST6Gal-I upregulated Hca-P. In addition, Hepa1-6 cells formed significantly larger tumors and suppressed intratumoral penetration by CD8+ T cells. In combination, these results suggest that ST6Gal-I promotes the immune escape of hepatocarcinoma cells in the tumor microenvironment and highlight the importance of assessing ST6Gal-I status for immunotherapies.