Targeted therapy for high-grade serous ovarian cancer (HGSOC) is difficult because HGSOC is defined by defective DNA-damage repair, not driver mutations. This makes it difficult to match a given patient to a drug based on a target mutation in their tumor. FDA-approved PARP inhibitor (PARPi) therapies that inhibit DNA-damage repair activity of PARP in tumor cells, do not work in advanced stages of the disease due to patients developing resistance. One of the few commonalities among HGSOC cases is expression of PAX8. We have identified where PAX8 binds to the DNA in benign vs malignant ovarian cancer cells. This information can help design a therapeutic that will be activated only in the presence of PAX8. A piece of DNA is enveloped by a biocompatible polymer and further modified to target it to ovarian cancer. Once delivered, PAX8 binding will activate and transcribe this piece of DNA that will contain a gene-editing domain to edit the PLK1 or ATR gene. Editing this gene in ovarian cancer with pre-existing mutations results in synthetic lethality and selective ovarian cancer cell death. Following up with clinically approved PARPi can enhance clinical effectiveness and improve patient outcome, thus rendering a highly specific treatment for HGSOC.
Background: Targeted therapy for high-grade serous ovarian cancer (HGSOC) is challenging as the disease is characterized by copy number variation rather than recurrent somatic mutations. HGSOC displays well-conserved epigenetic features such as PAX8 expression. We propose employing therapies that capitalize on interactions between PAX8 and DNA-binding sites to target HGSOC.
Methods: PAX8-expressing ovarian cancer cells or PAX8-negative cells were transfected with polyplexes bearing the plasmid of interest. Diameter, polydispersity indices and zeta potentials were measured. Polyplexes uptake, functionality and toxicity was assessed in vitro. In vivo experiments to demonstrate luciferase plasmid-bearing polyplexes have been performed in NOD- SCID mice.
Results: We have synthesized sub-200nm polyplexes using the polyamine PPLG-g- azidopropylamine and BE or gRNA plasmids. Using -/-PLK1 gRNA, we observed that the BE and the gRNA can be efficiently packaged into two distinct polymeric nanoplexes and co-delivered to impart a dominant negative mutant of PLK1, which is also synthetically lethal with mutated tp53, as observed from cancer cell death compared to controls.
Conclusion: Well-defined lineage transcription factors have potential to serve as novel targets for therapies in ovarian cancer. Combining nanotechnology and gene editing can improve specificity toward ovarian cancer and incorporate precision therapy aimed at underlying genetic architecture of this disease.