Project Summary Currently approved immunotherapies have shown efficacy in patients with immunogenic tumor types, such as melanoma and non-small cell lung cancer. However, immunotherapies are less effective for tumors with low levels of infiltrating lymphocytes and a low mutation rate, limiting the number of primed T cells within the tumor microenvironment. Our laboratory has developed a DNA vaccine platform using synthetic consensus sequences to break tolerance to germline antigens. These vaccines can break tolerance to native proteins in mouse models and induce anti-tumor activity. However, DNA vaccines are still limited by the immune suppressive microenvironment, which prevents CD8 T cell infiltration and activation within the tumor. Specifically, the extracellular matrix glycosaminoglycan high-molecular-weight (hmw) hyaluronan (HA) is abundant in the tumor microenvironment and is known to restrict T cell activation in other (non-tumor) contexts through engagement of CD44. Hyaluronidase is an enzyme that converts hmwHA to low-molecular-weight (lmw) HA, which is known to engage the innate immune system through Toll-like Recptors (TLRs). Hyaluronidase treatment of pancreatic and prostate cancers was also shown to enhance angiogenesis and improve chemotherapeutic delivery. We therefore hypothesize that hyaluronidase treatment in the tumor microenvironment will enhance T cell infiltration and activation in tumors resulting in improved efficacy when combined with DNA vaccine immunotherapy in a pancreatic cancer model. We show in preliminary experiments that combination therapy with hyaluronidase and vaccination in a prostate cancer model induced complete tumor regressions in over half of the mice, while treatment with either vaccine alone or hyaluronidase alone did not induce any complete regressions. Our first aim is to characterize changes to the tumor microenvironment upon hyaluronidase treatment in combination with our DNA vaccines, and to determine the specific contributions of hmw and lmw HA to these phenotypes. Our second aim is to determine the mechanism of action of this combination therapy using functional cellular depletion experiments, and agonistic or blocking antibodies to HA receptors. " |