208. Neural Stem Cell Mediated Oncolytic Virotherapy for Ovarian Cancer

Intro. Oncolytic virotherapy is a promising novel cancer treatment that uses replication-competent viruses to induce cancer cell death. While clinical trials are underway for a variety of solid tumors; success has been hampered by rapid immune-mediated clearance/neutralization of the viral vectors, and poor viral distribution to tumor satellites dispersed throughout normal tissue. Neural stem cells (NSCs) are ideal cell carriers that could overcome viral delivery hurdles due to their intrinsic tumor-tropism and penetration capabilities. Our lab has established a well-characterized, non-immunogenic human NSC line that can selectively distribute to many different solid tumors. Most recently, we observed impressive selectivity and penetration of peritoneal ovarian cancer metastases after intraperitoneal NSC administration. We have engineered our NSCs to produce a conditionally replication-competent adenovirus, CRad-Survivin-pk7 (NSC.CRad-S-pk7). This virus has two notable genetic modifications: (1) a polylysine fiber addition that enables high affinity binding to cell-surface proteoglycans, thus promoting viral entry into the target cell; and (2) a E1A transcriptional modification which prevents viral replication in the the absence of the surviving promoter, a gene over-expressed in many cancers. Clinical grade equivalent research banks of the NSC. CRad-S-pk7 cells have demonstrated safety and efficacy in orthotopic glioma models, but have not yet been tested in a metastatic ovarian cancer model. We hypothesize that NSCs are able to selectively distribute this virus to ovarian metastases, and provide protection from immune-mediated clearance and neutralization. Our long-term goal is to demonstrate efficacy and safety of NSC. CRad-S-pk7 for targeted selective tumor killing in patients suffering from stage III ovarian cancer. Methods. Two million NSC and NSC. CRad-S-pk7 cells were injected IP into nude mice containing established human peritoneal ovarian (OVCAR8 and SKOV3) metastases. After 7 days, tissue was assessed for viral distribution and activity using standard immunological and tumor-lysate viral titration assays, respectively. Results. The results suggest that the viral payload does not interfere with the NSC tumor-tropism or penetration (Fig 1Fig 1). NSC-mediated viral distribution was confirmed via immunohistochemistry, and the presence of active virus within lysed peritoneal tumors was assessed. Significant tumor killing was observed in both OVCAR8 and SKOV3 ovarian cancer cells after 5 days of culture with diluted tumor lysates (1:10 and 1:100) derived from mice that received NSC. CRad-S-pk7 injections (Fig 2Fig 2). No killing was observed when cancer cells were cultured with tumor lysates derived from mice that received parental NSCs. These results demonstrate that NSC. CRad-S-pk7 can selectively penetrate peritoneal ovarian metastases and produce CRad-S-pk7 adenovirus following IP administration. Studies underway include free virus distribution and pharmacokinetic comparisons.View Large Image | Download PowerPoint SlideView Large Image | Download PowerPoint Slide