Abstract 5944: Relief of chromosomal instability-induced cGAS-STING signaling sensitizes STK11-mutant non-small cell lung cancer to immune checkpoint blockade
Authors: Caprio Lindsay A. , Hong Christy , Amin Amit Dipak , Tagore Somnath , Melms Johannes , Cai Luke , Wang Yiping , Ho Patricia , Mu Michael , Hibshoosh Hanina , Henick Brian , Wong Kwok K. , Bakhoum Samuel F. , Izar Benjamin 
Published: April 2023

Abstract
Non-small cell lung cancers (NSCLCs) harboring deletions or inactivating mutations in STK11 (encoding LKB1) are associated with treatment-resistance, including to immune checkpoint blockade, and poor survival, yet the underlying mechanisms are poorly understood.
Here, we combined multi-modal single-cell transcriptomics, whole-genome sequencing (WGS), and analysis of public data bases totaling &gt;10,000 NSCLC whole-exome sequencing (WES) and when available RNA (RNA-seq) profiles of AACR GENIE, MSK IMPACT, TCGA and CPTAC, high-content imaging, and functional assays, to determine genomic and mechanistic features of STK11-mutant NSCLC.
Across human WES/RNA-seq data, we find that STK11-mutant NSCLC have a significantly higher fraction of genome altered (FGA) and score strongly for the mRNA-based CIN70 signature compared to other NSCLC genotypes, overall indicating that these tumors have a higher degree of chromosomal instability (CIN). 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 CINhigh status in dynamic assays. Next, we show that tonic CIN-induced activation of cGAS-STING signaling, whose activation is typically thought of inducing type I interferon expression, results in strong suppression of anti-tumor immune signaling. Remarkably, genetic or pharmacologic suppression of cGAS, and thus depletion of the STING ligand cGAMP, results in reprogramming and re-sensitization of STK11-mutant models to cGAS-STING mediated type I interferon responses. Furthermore, we show that CIN promotes excessive production cGAMP in STK11-mutant models. We find upregulation of two ectonucleotidases (ENPP1 and CD73/NT5E) that hydrolyze exported cGAMP to adenosine, which may further contribute to the highly dysfunctional tumor-microenvironment observed in STK11-mutant tumors. Lastly, suppression of CIN through overexpression of mitotic-centromere associated kinesin (MCAK) in murine STK11-mutant models results in decreased tumor growth and sensitization to anti-PD1 therapy.
In summary, we define STK11-mutant as archetypical chromosomally form of NSCLC, provide mechanistic basis that corelates 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 Dipak Amin, Somnath Tagore, Johannes Melms, Luke Cai, Yiping Wang, Patricia Ho, Michael Mu, Hanina Hibshoosh, Brian Henick, Kwok K. Wong, Samuel F. 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 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5944.