Extracellular galectin 4 drives immune evasion and promotes T-cell apoptosis in pancreatic cancer [RNA-Seq]

Pancreatic ductal adenocarcinoma (PDAC) is characterized by rich deposits of extracellular matrix (ECM), affecting the pathophysiology of the disease. Here, we identified galectin 4 (gal 4) as a cancer cell produced protein deposited into the ECM of PDAC tumors and detected high circulating levels of gal 4 in PDAC patients. In orthotopic transplantation experiments we observed increased infiltration of T-cells and prolonged survival in immunocompetent mice transplanted with cancer cells with reduced expression of gal 4. Increased survival was not observed in immunodeficient RAG1-/- mice, demonstrating that the effect was mediated by the adaptive immune system. Furthermore, by performing single-cell RNA-sequencing we found that the myeloid compartment and cancer-associated fibroblast (CAF) subtypes were altered in the transplanted tumors. Reduced gal 4 expression was associated with higher proportion of myofibroblastic CAFs and reduced numbers of inflammatory CAFs. We also found higher proportions of M1 macrophages, T-cells and antigen presenting dendritic cells in tumors with reduced gal 4 expression. Using a co-culture system, we observed that extracellular gal 4 induced apoptosis in T-cells by binding CD3, resulting in anergy or induction of apoptosis. Hence, we show that gal 4 is involved in immune evasion and identify gal 4 as a promising drug target for overcoming immunosuppression in PDAC. Overall design: Bulk RNA-seq analysis of two murine pancreatic cancer organoid lines derived from the mT5 line described in Boj et al, 2015 (PMID: 25557080). A Galectin 4 shRNA knock-down organoid line (Gal4KD) was compared to a scramble control line in paired technical triplicates. Epcam+/Cd45-/Pdpn- cells were FACS sorted and sequencing libraries were made on 500 cells per sample.