Pancreatic ductal adenocarcinoma (PDA) remains one of the most aggressive cancers with a rising death rate. The treatment paradigm has not changed over the past three decades, with antimetabolite chemotherapy as the mainstay of treatment. Novel approaches to develop effective therapies are needed. Promoter-driven gene therapy exploits an overactive cancer- specific promoter to express a desired gene in a cancer cell. This exciting strategy has been studied extensively in PDA using viral vectors, but has stalled at the pre-clinical level due to limitations of viral therapy. In prior studies, we developd a non-viral nanotherapy in which a biodegradable polymer DNA vector is injected locally into tumors. Using this approach, delivery of diphtheria toxin A (DTA) placed under the control of a cancer-specific promoter resulted in tumor shrinkage in pre-clinical mouse models of ovarian and prostate cancer, as well as in vitro studies of PDA. We recently demonstrated effective systemic targeting of DNA in prostate cancer-bearing mice using a novel DNA dendrimer conjugated to a targeting peptide against the transferrin receptor (TFRC). TFRC is overexpressed in most tumors (including PDA), but not in normal cells. Complementary to these studies, we used a rigorous approach to identify 13 promising promoter candidates for gene therapy from over 2500 putative PDA biomarkers, and tested these proteins for expression in our patient samples. Based on this work, MUC1 was identified as the best candidate promoter for transcriptionally-driven nanotherapy, since it was tightly correlated with aggressive biology i these PDA samples, and previous gene therapy studies (all viral) established efficacy of the MUC1 promoter. In this proposal, we detail plans to develop a MUC1 promoter-driven construct and use a derivatized DNA dendrimer to target PDA cell lines in culture and systemically in pre-clinical PDA mouse models (xenografts and orthotopic tumors). We will use a MUC1 promoter-driven luciferase reporter to test specificity in cell lines and a promoter-driven DTA construct to test treatment efficacy, biodistribution, and non-specific toxicity in mice. We hypothesize that MUC1-expressing cells will be exquisitely sensitive to treatment in vitro, and MUC1 non-expressing cells will be resistant. Similarly, we expect stunted tumor growth in MUC1-expressing xenografts and improved survival in mice with MUC1-expressing orthotopic tumors. If effective, these studies will serve as a foundation for rapid testing of systemically administerd MUC1 promoter-driven nanoparticles in patients with PDA, followed by early phase-safety trials of DTA nanotherapy in patients.
Pancreatic cancer remains one of the most lethal cancers, with no effective treatments. To address this pressing clinical need, we will use preclinical mouse models to develop a systemic, non-viral, targeted gene therapy for the treatment of pancreatic cancer. A transferrin receptor ligand bound to a DNA-based dendrimer will serve as the vector for targeted and pancreatic cancer-specific delivery of a lethal DNA construct containing the MUC1 promoter and diphtheria toxin A sequence. Successful targeted DNA delivery following systemic administration would be a significant advance in the application of gene therapy for pancreatic cancer.
