Abstract 6657: Oncolytic Vaccinia Virus Carrying OPCML Tumor Suppressor is active in Epithelial Ovarian Cancer

Abstract Objective: Epithelial Ovarian cancer (EOC) has the highest mortality rate among gynecologic malignancies, necessitating novel therapeutic approaches. Viral oncolytic immunotherapy with recombinant oncolytic vaccinia virus (OVV) offers promise for advanced-stage cancer treatment. OPCML is a GPI-anchored 3 Ig-domain tumor suppressor inactivated by somatic methylation in 87% of EOC. OVV with OPCML (OVV-OPCML) gene insertion may have potential as a therapeutic agent. This study explores the oncolytic, signaling-inhibitory, anti-angiogenic and synergistic immunotherapeutic properties of OVV-OPCML in EOC treatment, evaluating its therapeutic potential. Methods: To create OVV-OPCML, the virulent vaccinia virus Copenhagen strain F3L site was modified with OPCML cDNA, confirmed by qPCR and western blot. Oncolytic potential was assessed through in vitro and in vivo EOC cell infection with OVV-OPCML. Real-time cell analysis (RTCA) assessed cell proliferation. Xenograft tumor models in nude mice were used to evaluate in vivo oncolytic activity, while OVV-OPCML combined with anti-PD-1 treatment was tested using a syngeneic orthotopic EOC mouse model (ID8) in C57BL/6 immunocompetent mice. Serum IFN-γ and TNF-α were quantified via ELISA. Receptor Tyrosine Kinases, angiogenesis and phosphorylation together with immune markers were examined by western blotting and by multiplex immunohistochemistry (mIHC) analysis of tumor sections. Results: OVV-OPCML selectively infected OC cells, leading to viral replication and tumor cell death, while sparing normal ovarian cells in-vitro. OPCML protein expression increased post-infection. OVV-OPCML reduced ERBB2, EGFR, and FGFR1 expression in SKVO3 OV cells. Intratumoral or intraperitoneal (IP) OVV-OPCML administration in human ovarian cancer nude mouse models reduced tumor growth and improved survival. IP in-vivo OVV-OPCML in combination with anti-PD-1 treatment in vivo, in the IP ID8 syngeneic model demonstrated synergy with survival improvement. H&E staining showed tumor cell damage without significant harm to normal tissues. Protein expression of ERBB2, EGFR, FGFR1, and their phosphorylated forms decreased. CD31, VEGFR2, p-VEGFR2 (Tyr1175), and p-VEGFR2 (Tyr1214) downregulation suggested tumor angiogenesis disruption. OVV-OPCML treatment elevated serum TNF-α and INF-γ levels and increased CD8+ T cells and PD-L1 expression in OVV-OPCML treated syngeneic tumors. Conclusions: OPCML gene enhances OVV selectivity against OC cells through direct oncolysis and OPCML protein production, inhibiting specific RTKs, suppressing angiogenesis, and activating antitumor immune responses synergistically with anti-PD-1. OVV-OPCML therapy shows promise as a targeted strategy for ovarian cancer treatment. Citation Format: Yong Tang, Yingzhao Liu, Mingjing Deng, Fei Huang, Jiahu Wang, Paul Blake, Hani Gabra, Qi Wang. Oncolytic Vaccinia Virus Carrying OPCML Tumor Suppressor is active in Epithelial Ovarian Cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6657.