Abstract A068: Post-transcriptional regulation driven by NAT10 in ovarian cancer

Introduction- Protein synthesis in cancer is frequently dysregulated, highlighting translational regulatory mechanisms as promising treatment targets. The epitranscriptome, which includes more than 140 chemical modifications of RNA, plays a significant role in regulating protein synthesis. For example, N-acetyltransferase 10 (NAT10), which acetylates cytidines (N4-acetylcytidine or ac4C) in RNA, is notably overexpressed in various cancers. However, the specific impact of RNA ac4C modification in high-grade serous ovarian cancer (HGSOC) remains incompletely understood. This project aims to characterize the underlying oncogenic mechanisms of the NAT10/ac4C axis. Methods: We performed acetylated RNA immunoprecipitation sequencing (acRIP-seq) to identify the mRNA targets of NAT10. To investigate the impact of NAT10-overexpressing macrophages on tumor progression, we utilized a Csf1r -/- ovarian cancer in vivo model. Furthermore, we employed flow cytometry to evaluate how NAT10 expression influences immune cell infiltration within the tumor microenvironment. Results: We observed that macrophages exposed to conditioned medium from ovarian cancer cells exhibit increased NAT10 expression, accompanied by elevated levels of RNA acetylation. Moreover, enhanced NAT10 expression in macrophages promotes an immunosuppressive phenotype, characterized by upregulation of CD206, IL-10, IL-1β, and Arginase. Flow cytometry analysis revealed that NAT10 overexpression in macrophages impairs T-cell infiltration and contributes to an immunosuppressive tumor microenvironment by reducing the population of activated T cells. Furthermore, inhibition of NAT10 in the tumor microenvironment reduces ovarian cancer growth in a mouse model. acRIP sequencing identified 978 differentially acetylated peaks, including 211 that were hyperacetylated. The associated genes were enriched in pathways related to mRNA processing, ribosome biogenesis, RNA splicing, and regulation of translation initiation. Conclusions: Our study provides a novel mechanism by which macrophages within a tumor microenvironment acquire their immunosuppressive phenotype and identifies an important link among mRNA acetylation, macrophage immunosuppression, and tumor progression. This study suggests a new strategy for restoring the anti-tumor phenotype of macrophages by reducing NAT10 expression. Citation Format: Sonam Mittal, Shirng-Wern Tsaih, Ishaque Pulikkal Kadamberi, Sudhir Kumar, Mona Singh, Chandrima Dey, Jasmine George, Rahimi Arezou, Anjali Geethadevi, Anupama A Nair, Pradeep Chaluvally-Raghavan, Sunila Pradeep. Post-transcriptional regulation driven by NAT10 in ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr A068.