Enhancing intratumoral T cell infiltration by deliver of shCXCL5 in a Plectin targeted AAV to improve checkpoint blockade efficacy - ABSTRACT Pancreatic Ductal Adenocarcinoma (PDAC) is a highly lethal disease and is expected to become the second leading cause of cancer-associated-death in the US by the year 2025. Targeted therapeutics have failed to provide a significant survival advantage over the standard of care. With an intensified focus on immunotherapy, immune checkpoint blockade (ICB) therapies alone have been insufficient for PDAC, which often displays a non- immunogenic “cold” tumor phenotype that lacks cytotoxic T lymphocyte (CTL) infiltration, thus incapable of invoking an immune response. To this point, we have learned that multiple biological and molecular aspects of PDAC contribute to ICB efficacy; including antigenicity, immunogenicity, and the tumor microenvironment. Finding targeted therapeutics to increase these aspects of immunity and increase intratumoral T cell infiltration are essential for improving immunotherapeutic applications for PDAC. Obesity is a prominent risk factor for development of PDAC as well as more advanced disease. Obesity is well evidenced to drive local adipose inflammation, but also contributes to systemic inflammation. Our recent findings indicate adipose derived cytokines directly modulate the transcriptional profile of PDAC cells. Specifically, we found that stimulation of PDAC cells with adipose conditioned media promoted anti-immunogenic chemokine secretion of tumor-derived CXCL5, which is a ligand of the CXCR1/2 receptors that typically regulates myeloid recruitment and/or activation. While clinical trials targeting the CXCR1/2 receptors with pharmacologic inhibitors have entered clinical trials, their efficacy in PDAC is questionable due to broad receptor expression and conflicting results. In comparison, our studies have demonstrated that depleting tumor derived CXCL5, one of many CXCR1/2 ligands, is sufficient to promote intratumoral CTL infiltration and prime the tumor for checkpoint inhibition in the setting of obesity. In general, targeting pancreatic cancers with cell-specific biomarkers has presented a challenge to researchers, as some biomarkers of PDAC are highly expressed in non-cancerous tissues and limiting drug delivery to non-cancerous tissue is essential for minimizing side effects. The Plectin protein represents an ideal biomarker for targeted therapeutic delivery. In healthy cells, Plectin maintains a cytoplasmic localization where it is hidden from targeted therapeutics. Alternatively, Plectin is exclusively externalized in pancreatic cancer cells where it provides an optimal target for drug delivery. Proof of principle studies have validated PDAC specific binding of Plectin targeted AAV viral particles. We plan to package shRNA for CXCL5 into the Plectin-AAV particles to recapitulate our CRISPR studies and induce susceptibility to ICB therapy in an obese setting.
