N-glycans in non-malignant tumor microenvironment cells dampen CAR-T cell function in solid tumors.

Chimeric antigen receptor (CAR) T-cell therapy has shown limited efficacy in solid tumors, largely due to immunosuppressive mechanisms within the tumor microenvironment (TME). While tumor-associated glycans are known to protect malignant cells from immune attack, the contribution of N-glycans expressed by non-malignant TME populations to CAR-T cell dysfunction remains poorly defined. We investigated the role of N-glycans in non-malignant TME populations, focusing on M2-like macrophages and hepatic stellate cells in liver metastasis of colorectal (CRC) and pancreatic cancer (PDAC). Using in vitro co-culture systems, transcriptomic analysis, and tumor-bearing humanized mouse models, we assessed how pharmacologic or genetic disruption of key nodes of the N-glycosylation pathway (MGAT5, MAN2A1 and ST6GAL1) in immune and stromal compartments shapes T-cell function.

In patient samples, a branched N-glycan signature was associated with transcriptional programs characteristic of tumor-promoting macrophages and stromal cells, linking N-glycosylation to an immunosuppressive TME. Disruption of N-glycan synthesis in non-malignant TME cells reduced their immunosuppressive and tumor-supporting functions. Single-cell RNA sequencing of tumor-bearing humanized mice showed depletion of protumor IL1β+ macrophages and diminished inhibitory macrophage-T cell interactions following N-glycosylation blockade. Selective MGAT5 disruption in immune and stromal compartments suppressed immunosuppressive programs and enhanced CAR-T cell antitumor activity independently of tumor cell glycosylation.

These findings show that N-glycans expressed by non-malignant TME cells restrain CAR-T cell responses in CRC and PDAC, highlighting MGAT5-dependent branching as a potentially actionable axis and supporting a broader role for multiple nodes of the N-glycosylation pathway.