Abstract 4469: Disruption of ATG9A-dependent basal autophagy sensitizes cancer cells to innate inflammatory signaling

Abstract Pathogen-derived nucleic acids are recognized by pattern recognition receptors (PRRs), including cGAS and RIG-I, which trigger the innate immune response by activating IRF3-mediated interferon gene expression. In tumors, high levels of chromosomal instability can also lead to DNA fragments leaking into the cytosol to trigger PRR-mediated interferon response, resulting in pro-inflammatory cytokine secretion from the tumor. This could potentially expose tumor cells to immune attack. However, through mechanisms that are not completely understood, tumor cells dampen the interferon response to escape immune recognition. Previous work demonstrated that loss of ATG9A, but not ATG5, increased inflammatory signaling through the STING-IRF3 cascade, suggesting that perhaps an autophagy-independent function of ATG9A regulates inflammation. Here we found that loss of ATG9A or other upstream regulators of basal autophagy (e.g., ATG101), but not core LC3 lipidation machinery (ATG5 or ATG7), sensitizes cells to dsDNA-induced IRF3 activation and interferon gene expression. We also found that loss of ATG9A or ATG101, but not ATG5 or ATG7, increases the basal activity of the ubiquitin-sensing, IRF3-targeted kinase TBK1, which increases further upon dsDNA treatment. In these ATG9A and ATG101 deficient cells, TBK1 is clustered around large p62-positive condensates that previously been shown to contain large accumulations of LC3. Our preliminary data suggest a model in which ATG9A deletion causes the accumulation of LC3-positive membrane at p62 condensates, which may act as a platform for inflammatory signaling. Our current work focuses on identifying the upstream pathways and core mechanism that regulates IRF3 activation in ATG9A-deficient cells and exploiting this mechanism to improve anti-tumor immunity. Citation Format: Dasun N. Jayatunge, Tsz-Ming Tsang, Colten M. McEwan, Joshua L. Andersen. Disruption of ATG9A-dependent basal autophagy sensitizes cancer cells to innate inflammatory signaling. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4469.