301. Safe and Effective Treatment of Ovarian Cancer Models Using Targeted Adenovirus Vector Delivery and Selective Expression of Tumor Necrosis Factor

Abstract

Ovarian cancer is the fourth most common cancer among women, and despite advances in therapy most patients still die as a consequence of disease that is disseminated within the peritoneal cavity. Delivery of hTNFa gene to tumors using direct intra-tumoral injection of a non-replicating adenovector is a promising strategy for treatment for a variety of diseases. The relative abundance of the coxsackie and adenovirus receptor (CAR) in the mesothelial lining of the peritoneal space and paucity of CAR in tumors may limit on the use of un-targeted adenovectors administered to the peritoneal cavity. To enhance selectivity of TNFa exposure to the tumor we combined two approaches. We modified adneovector capsids to limit transduction of normal cells. We analyzed the ability of Ad5 based vectors in which the fiber and penton base binding interactions were deleted. To allow tumor uptake we incorporated a RGD-4C motif in the fiber knob (Ad|[ast]||[ast]|RGD) to target |[alpha]|v|[beta]|3/5 integrins receptors that are highly expressed in tumor and sparsely expressed in the epithelial layer of peritoneum. Ad|[ast]||[ast]|RGD vector exhibits effective gene transfer in a variety of ovarian cancer cell lines that we examined in vitro and in vivo. Importantly, the Ad|[ast]||[ast]|RGD vector has a capability to target ovarian tumor nodules and avoid infecting the normal mesothelial cells that line the intraperitoneal space of athymic nude mice following intraperitoneal (ip) administration. We have now added an additional level of control by placing the TNFa expression under the control of tumor selective promoters. These promoters were incorporated into the capsid-modified vector to confer the expression of human tumor necrosis factor alpha (hTNFa) therapeutic gene. We compared both constitutive (CMV or RSV) and tumor selective promoters (DF3, E2F or hTERT) for safety and efficacy in human ovarian cancer models. Vector containing capsid targeting combined with the DF3 promoter expression control was shown to reduce tumor burden in the human ovarian cancer models (Caov3 and Igrov1) following ip administration. The DF3 vector was well tolerated with no evidence of body weight changes, and limited exposure to systemic TNFa at the effective dose (1.2e11 pu/20g). Together, our data support a strategy of combining receptor targeting combined with expression control of TNFa as a potential gene delivery mechanism for ovarian cancer treatment.