Pancreatic ductal adenocarcinoma (PDA) is the third leading cause of cancer-related death in the United States and survival rates have only marginally improved in recent decades. Conventional cytotoxic agents remain the standard of care, and mainly target cancer genome integrity. A search for alternative therapeutic strategies is critical to bend the survival curve and save lives. The pancreatic cancer microenvironment provides a promising opportunity, because it creates metabolic vulnerabilities in PDA cells that do not exist in normal cells (i.e., a therapeutic window). The PDA microenvironment comprises 80% of the tumor mass, and is characterized by a dense, poorly vascularized stroma. Such austere, hypoxic conditions and nutrient-deprived conditions result in a highly oxidative state, which necessitates a robust anti-oxidant response just to survive these conditions, along with other insults like chemotherapy. The antioxidant defense system is complex and multi-pronged, but nearly the entire mechanism is dependent upon the ultimate reductive currency of the cell: NADPH. Along with my lab colleagues, I have shown that one of the NADPH synthesizing enzymes, cytosolic isocitrate dehydrogenase 1 (IDH1), is especially important to PDA cells for this purpose. For instance, knockout of IDH1 using CRISPR gene editing sensitizes PDA cells to nutrient conditions present in the austere PDA microenvironment, and markedly impaired xenograft tumor growth. Herein, we aim to decipher the role of the two key byproducts of IDH1 in PDA adaptive survival under low nutrient stress: NADPH and ?-ketoglutarate (Aim 1). Our preliminary discoveries suggest that both of these byproducts impact redox homeostasis and mitochondrial function, and cell-based and metabolomics studies in this proposal will elucidate the mechanisms of IDH1-driven adaptive survival and growth. Moreover, this work will further validate IDH1 as a promising therapeutic target. Additionally, we will work with our long-standing collaborators at Genisphere (Co-Sponsor Dr. Getts) to develop a new therapeutic strategy to target IDH1 in PDA cells (Aim 2). In this aim, we build on preliminary data to test a novel biodegradable DNA- dendrimer derivatized with si.IDH1 oligos (3DNA-si.IDH1). We recently demonstrated effective IDH1 mRNA silencing after systemic injection of 3DNA-si.IDH1 in nude mice bearing PDA xenografts. Herein, we will test systemic efficacy in orthotopic and autochthonous PDA mouse models. Through the work detailed in this proposal, along with the training plan under the mentorship of Drs. Winter, Brody, Getts and Brunengraber, I will have the opportunity to catapult my career and lay the foundation to achieve my dream as an independent cancer researcher.
Pancreatic cancer is an outlier disease, with the highest mortality among the common cancers and no new treatments beyond conventional chemotherapy. This proposal indicates that metabolic dependencies exist related to the austere tumor microenvironment, and that the metabolic enzyme, isocitrate dehydrogenase 1 (IDH1), protect pancreatic cancer cells under these conditions through enhanced antioxidant defense and mitochondrial function. We propose a novel and systemic DNA dendrimer nanotherapy specifically targeting IDH1 gene expression in an animal model.
