Abstract 5360: Relief of chromosomal instability-induced cGAS-STING signaling sensitizes STK11-mutant non-small cell lung cancer to immune checkpoint blockade

Abstract Non-small cell lung cancers (NSCLCs) harboring deletions or inactivating mutations in STK11 (encoding LKB1) are associated with poor prognosis and immune evasion, but the underlying mechanisms are poorly understood. Through integrative analyses of 10, 000 molecular profiles from public data sources and an additional ~15, 000 new patient data profiles, we find identify STK11-deficient NSCLC as an archetypical chromosomally unstable tumor. Using high-content imaging, we show that both human and murine STK11-mutant models have a higher rate of micronuclei and chromosome mis-segregation events, confirming their high degree of chromosomal instability (CIN). We show that CIN-induced tonic activation of the cGAS-STING pathway results in impaired type I interferon expression, thus, turning the physiological function of this pathway on its head. We show that temporary relief of tonic CIN-induced signaling reprogrammed cancer cells towards production of type I interferons. We achieved this through orthogonal routes, including genetic suppression of CIN by overexpression of mitotic centromere-associated kinesin (MCAK), rescue of wild-type STK11 (but not its kinase-dead) allele, genetic deletion or pharmacological inhibition of cGAS. Relief through any of these approaches re-sensitized cells to acute STING agonism with its endogenous ligand (cGAMP) or pharmacological stimulation. Using otherwise isogenic, syngeneic KRAS-mutant Stk11/Lkb1-/- (KL) and KRAS-mutant p53 mutant (KP) murine models, we show that cGAS KO sensitized otherwise highly resistant KL models to immune checkpoint blockade (ICB), while an increase in CIN (through overexpression of dominant-negative MCAK) in KP conferred resistance in this otherwise ICB-sensitive model. In summary, we define STK11-mutant as archetypical chromosomally unstable form of NSCLC, provide mechanistic basis that correlates with poor clinical outcomes, and demonstrate how relief of tonic CIN-induced changes may be therapeutically leveraged. Citation Format: Lindsay A. Caprio, Christy Hong, Amit D. Amin, Somnath Tagore, Mercedes Duran, Meri Rogava, Luke Cai, Leon Ebel, Johannes Melms, Hanina Hibshoosh, Samuel Bakhoum, Benjamin Izar. Relief of chromosomal instability-induced cGAS-STING signaling sensitizes STK11-mutant non-small cell lung cancer to immune checkpoint blockade 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 5360.