Abstract 488: Modulation of ENPP1 activity and 2'3'-cGAMP degradation in ovarian cancer cell lines via loadable pre-formed lipid nanoparticles

Abstract Ovarian cancer is a complex heterogeneous disease with various subtypes and diverse molecular mechanisms of pathogenesis. Among different forms, epithelial ovarian cancer is the most common, representing up to 90% of total reported cases. Due to the lack of early diagnostic tools, the prognosis is mainly poor, as most cases are typically identified in advanced stages. Thus, a more thorough understanding of the inherent complexities of the disease, in terms of its biochemical etiology, will allow for identification of specific molecular and genetic profiles that could lead to more effective treatment plans. Recent studies have shown that ENPP1 may play a role in cancer cell proliferation, migration, and invasion in ovarian and other types of cancer. ENPP1 is a glycosylated type II transmembrane protein acting as a pyrophosphatase and phosphodiesterase with broad specificity. ENPP1 substrates include mononucleotides and cyclic dinucleotides such as the second messenger, 2'3'-cGAMP, which binds to and activates STING. 2'3'-cGAMP is exported extracellularly by cancerous cells into the tumor microenvironment where uptake into neighboring cells can activate their STING-dependent type 1 interferon pathway and promote antitumoral immune responses. ENPP1 can hydrolyze extracellular 2'3'-cGAMP however, allowing cancer cells to evade such an immune response. In this study, we assessed the activity of ENPP1 in CaOV-3, SK-OV-3, and PA-1 ovarian cancer cell lines using a fluorometric cell-based assay. The effects of ENPP1 inhibition via a chemical inhibitor on extracellular 2'3'-cGAMP levels were characterized and compared with siRNA-mediated knockdown of ENPP1 via loadable pre-formed lipid nanoparticles, which enable small-scale encapsulation and transfection of nucleic acid cargo. In addition, we explored whether uptake of exogenous 2'3'-cGAMP into THP-1 and RAW immune cell lines can be enhanced through delivery via preformed loadable lipid nanoparticles. Corresponding immune cell activation was also assessed using immunoblotting and RT-PCR. Our results demonstrate how modulation of ENPP1 activity and 2'3'-cGAMP levels in ovarian cancer cell lines using unconventional, pre-formed loadable lipid nanoparticle transfection reagent can aid in elucidating mechanisms of immune evasion in cancer cells. Citation Format: David Taylor, Jiajia Ji, Phillip Rzeczycki, Margaret L. Collins, Lauren Clements, Aileen R. Ariosa. Modulation of ENPP1 activity and 2'3'-cGAMP degradation in ovarian cancer cell lines via loadable pre-formed lipid nanoparticles 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 (6Suppl): Abstract nr 488.