Abstract PR-10: AXL limits the mobilization of cholesterol to regulate dendritic cell maturation and the immunogenic response to cancer

Abstract Our prior research established that the uptake of tumor debris induces maturation in conventional dendritic cells (cDCs), transforming them into a molecular state termed mature DCs enriched in immunoregulatory molecules 'mregDC.' This state entails a dampened ability to acquire new antigens, upregulated chemokine receptors for migration to lymphoid organs, and increased expression of MHC-I and -II, costimulatory, and -inhibitory molecules, promoting the differentiation of antigen-specific T cells. Understanding the molecular dynamics accompanying the uptake of tumor debris cargo by DCs is crucial, addressing a significant gap in our comprehension of DC immunogenicity regulation. To bridge this knowledge gap, we meticulously analyzed publicly available single-cell RNA sequencing data from human and murine DCs across various tumor models. This investigation revealed a cluster of genes within the mregDC program associated with enzymes participating in cholesterol metabolism. We postulated that this metabolic shift plays a crucial role in the establishment of the mregDC state. To validate this hypothesis, we purified mregDC from mice injected with a lung cancer experimental model or from an in vitro reductionist model designed to generate mregDC by feeding cDCs with tumor apoptotic cargo. Subsequently, we selectively perturbed components of cholesterol metabolism using various inhibitors to define their impact on cDC maturation into the mregDC state. Our findings demonstrate that cholesterol mobilization, encompassing both de novo synthesis and acquisition during debris uptake, propels cDCs towards mregDC maturation. This cholesterol is utilized to form lipid nanodomains on the plasma membrane of mregDCs, facilitating the expression of maturation markers on the cell surface. Crucially, this process relies on both de novo synthesis and the involvement of Niemann-Pick disease type C1 (NPC1), a mediator of cholesterol transport from the endolysosomal pathway. NPC1 specifically contributes to the accumulation maturation markers including IFN-ɣ receptor (IFNɣR) in lipid nanodomains, optimizing IFNɣR signaling crucial for IL-12 production and efficient T cell activation. Our research further reveals that the receptor tyrosine kinase AXL consistently inhibits the cholesterol-dependent formation of lipid nanodomains on mregDCs. Deleting AXL from cDCs enhances mregDC immunogenicity, resulting in potent anti-tumor immunity. In summary, our study provides groundbreaking insights into the mobilization of cholesterol as a fundamental component for immune receptor signaling during cDC maturation. Additionally, it highlights AXL as a central regulator of this process, suggesting therapeutic targeting of AXL to harness the immunostimulatory potential of DCs in lung cancer patients. Citation Format: Meriem Belabed, Matthew D Park, Cédric M Blouin, Sreekumar Balan, Chang Y Moon, Grace Freed, Miguel Quijada-Álamo, Raphaël Mattiuz, Amanda M Reid, Nader Yatim, Jesse Boumelha, Camillia S Azimi, Nelson M LaMarche, Leanna Troncoso, Jessica Le Berichel, Steven T Chen, Matthias C Wilk, Brian D Brown, Kristen Radford, Sourav Ghosh, Carla V Rothlin, Laurent Yvan-Charvet, Thomas U Marron, Daniel J Puleston, Elvin Wagenblast, Nina Bhardwaj, Christophe Lamaze, Miriam Merad. AXL limits the mobilization of cholesterol to regulate dendritic cell maturation and the immunogenic response to cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr PR-10.