Abstract PR009: SMARCAL1 is a dual regulator of innate immune signaling and PD-L1 expression that promotes tumor immune evasion

Abstract Genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection. However, cancer cells often evade these responses by overexpressing immune checkpoint regulators, such as PD-L1. Here, we identify the SNF2-family DNA translocase SMARCAL1 as a factor that favors tumor immune evasion by a dual mechanism involving both the suppression of innate immune signaling and the induction of PD-L1-mediated immune checkpoint responses. Mechanistically, SMARCAL1 relieves endogenous DNA damage and suppresses cGAS-STING-dependent immune signaling during cancer cell growth. Simultaneously, it cooperates with the AP-1 family member JUN to maintain chromatin accessibility at a transcriptional regulatory element in the PD-L1 gene, thereby promoting PD-L1 expression in cancer cells. Loss of SMARCAL1 enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a valuable target for cancer immunotherapy. Citation Format: Giuseppe Leuzzi, Alessandro Vasciaveo, Angelo Taglialatela, Xiao Chen, Tessa M. Firestone, Allison R. Hickman, Wendy Mao, Tanay Thakar, Alina Vaitsiankova, Jen-Wei Huang, Raquel Cuella-Martin, Samuel B. Hayward, Jordan S. Kesner, Ali Ghasemzadeh, Tarun S. Nambiar, Patricia Ho, Alexander Rialdi, Maxime Hebrard, Yinglu Li, Jinmei Gao, Saarang Gopinath, Oluwatobi A. Adeleke, Bryan Venters, Charles G. Drake, Richard Baer, Benjamin Izar, Ernesto Guccione, Michael-Christopher Keogh, Raphael Guerois, Lu Sun, Chao Lu, Andrea Califano, Alberto Ciccia. SMARCAL1 is a dual regulator of innate immune signaling and PD-L1 expression that promotes tumor immune evasion [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr PR009.