Role of oncofetal glycosaminoglycans (OFGAG) for the immune privilege of pancreatic cancer

Pancreatic cancer is a devastating disease with very low 5-year survival and effective therapies are still missing. Conclusive evidence, down to the single cell, demonstrates that cancer stem cells (CSCs) represent the root of this disease by giving rise to all differentiated progenies within each cancer subclone. Importantly, CSCs are essential for the metastatic behaviour of tumours and, due to their inherent chemoresistance, represent an important source for disease relapse. We recently discovered that oncofetal glycosaminoglycans (OFGAG) are strongly expressed on pancreatic CSCs, differentiated pancreatic cancer cells, and pancreatic cancer-associated fibroblasts (CAFs), while being absent on normal tissue. OFGAG have been reported to play an immunosuppressive role. Indeed, we found significantly reduced cytotoxic T cell response upon inhibition of OFGAG. Hence, the aim of this PhD project will be to further elucidate the effects of inhibition of OFGAG on pancreatic CSCs, their differentiated progenies, and pancreatic CAFs. We will particularly focus on potential alterations in the self-renewal capacity of pancreatic CSC and tumourigenicity in vivo. OFGAGs will be inhibited by treatment with OFGAG chain terminating xylosides or anti-OFGAG CAR T-cells using OFGAG binding domains of the malaria protein VAR2CSA. Reversal of immunosuppression will be studied by flow cytometry and IHC analysis of tumours in vivo. Specifically, immunosuppressive checkpoint molecules, e.g. PD-1, CTLA-4, and Tim-3 on T-cells, numbers of Foxp3+ regulatory T-cells, immunosuppressive CD39+ gd TCR+ T-cells, and myeloid-derived suppressor cells will be examined. Functional changes in the T-cell compartment will be investigated in cytotoxicity assays against the cancer (stem) cells. In vivo tumourigenicity will be visualized by tracking luciferase+ pancreatic cancer (stem) cells. As such, this project will provide novel insights into the immunomodulatory role of oncofetal glycosaminoglycans in pancreatic cancer and provide two different therapeutic approaches that bear the potential to improve the outcome of this still fatal disease.

Rotation project:
Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic cancer with still very low 5-year survival. Studies based on patient-derived tissue samples suggested that cancer stem cells (CSCs) represent the root of PDAC and are essential drivers in metastasis, chemoresistance and disease relapse. We noted that CSCs are highly protected from immune surveillance including cytotoxic T cells. In contrast to differentiated pancreatic cancer cells, CSCs selectively expressed peptidoglycan recognition (PGRP) protein. PGRP are conserved from insects to mammals and recognize and destroy bacterial peptidoglycan. We created PGRP mutants by CRISPR/Cas9 and currently investigate the underlying mechanisms by which PGRP provide immune escape. We already showed that T-cells cultured in the presence of PGRP mutants have lower expression of the inhibitory checkpoint molecule PD-1 suggesting that CSC-released PGRP regulate expression of PD-1. Using PGRP mutant CSC, during the rotation project the student will investigate whether PGRPs affect the expression of Tim-3, another inhibitory checkpoint molecule, in CSC surrounding T-cells by regulating expression of galectin-9 in CSC. This project will provide insights into the immunomodulatory role of PGRP in pancreatic cancer.

Skills Priority Alignment: Whole Organism, Advanced Therapeutics, Quantitative Biology