Disabling PSGL-1 abrogates immune suppression and resistance to PD-1 blockade in pancreatic cancer.

[UNLABELLED] Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer for which there is a critical need to identify novel therapeutic targets. Herein we define PSGL-1 as a checkpoint inhibitor using a syngeneic orthotopic model of PDAC. As with PDAC patients, CD8 T cells within murine PDAC tumors expressed high levels of PSGL-1. PSGL-1 mice displayed striking T cell-dependent control of primary tumors and lung metastases. Extensive spatial remodeling within PDAC tumors occurred in PSGL-1 mice with a dramatic loss of proliferating tumor cells and an increase in CD8 T cell engagement of antigen-presenting cells. The prominent CD8 T cell infiltrates included subsets of pre-exhausted T cells retaining hallmarks of stemness and multifunctional effector capacity. These changes enabled a near complete response of PDAC to therapeutic PD-1 blockade. Our findings identify PSGL-1 as a key regulator of anti-tumor immunity in PDAC, highlighting its potential as a therapeutic target to limit CD8 T cell exhaustion and enhance immunotherapy response.

[SUMMARY] Hope describe a pivotal function of PSGL-1 in CD8 T cell responses to pancreatic ductal adenocarcinoma. Genetic deletion of PSGL-1 elicits tumor control by increasing T cell infiltration and maintaining functional subsets, thereby promoting sensitivity to PD-1 blockade.