The surface alpha-enolase targeting as a novel immunotherapeutical strategy for pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDA) is a very aggressive tumor for which effective therapeutical strategies are still lacking. The global five-years survival is of 5% and surgery is the only potentially curative treatment. The PDA-associated antigen α-enolase (ENO1), beside its glycolytic function, acts as a plasminogen receptor, promoting activation into plasmin, involved in extracellular matrix degradation. Antibodies against ENO1 are detected in more than 60% of PDA patients and correlate with a better prognosis. Furthermore, anti-ENO1 antibodies are induced in mice after ENO1-DNA vaccination. We observed an increased ENO1 expression on the cell surface of both PDA and myeloid cells (MDSC), suggesting a role in tumor progression and spreading. The immunotherapy represents a chance to selectively target PDA cells and MDSC. Mouse anti-human ENO1 monoclonal antibody (mAb) inhibits plasminogen-dependent invasion of human PDA cells and metastatic spreading in immunosuppressed mice, as well as MDSC adhesion to pancreatic endothelial cells and in vitro and in vivo migration. Similarly MDSC arginase activity and secretion of IL-6 decrease after ENO1 triggering, while anti-ENO1 treatment does not affect costimulatory molecule expression and MDSC suppression functions. Notably, a single administration of Adeno-Associated Virus (AAV)-expressing an anti-ENO1 mAb reduced the number of lung metastases in immunosuppressed mice injected with PDA cells. In conclusion, the antibodies anti-ENO1 may inhibit PDA cell and myeloid cell invasion and modulate T cell response, making the immunotherapy more effective.