Abstract

The limited effectiveness of T cell-based immune checkpoint blockade (ICB) therapy in most patients with pancreatic ductal adenocarcinoma (PDAC) is largely due to poor CD8 + T cell infiltration and a highly immunosuppressive microenvironment driven by excessive myeloid cell accumulation. This highlights the urgent need for new immunotherapy targets and strategies. In this study, an identified pro-cancer factor, cancer cell-derived sialylated IgG (SIA-IgG), is found to be significantly overexpressed in pancreatic cancer cells. SIA-IgG inhibits macrophage phagocytosis and induces an M2-like immunosuppressive phenotype through interactions with Siglec-7/9/10. SIA-IgG and TGF-β1, a key immunosuppressive factor, reinforce each other in a positive feedback loop, promoting immune evasion in PDAC. Blocking SIA-IgG with specific monoclonal antibodies shows significant therapeutic potential through reversal of PDAC’s immunosuppressive microenvironment. Our findings identify the SIA-IgG/Siglec axis as an immunotherapeutic target for PDAC, offering a feasible approach for the development of immunotherapeutic strategies.