Abstract LB014: Targeting Stearoyl-coA desaturase (SCD) as a therapeutic strategy in STK11/KEAP1 co-mutant non-small cell lung cancer
Authors: Sen Utsav , Sen Triparna 
Published: April 2023

Abstract
Introduction: Non-small cell lung cancer (NSCLC) is a highly prevalent subtype of lung cancer. Recent findings in the field have improved the clinical outcomes for only a subset of patients who are responsive to immunotherapy or have targetable oncogenic drivers. We have previously showed that concomitant loss of Serine/Threonine Kinase 11 (STK11) and Kelch-like ECH Associated Protein1 (KEAP1) detected in up to 10% NSCLC cases, dramatically enhances cell proliferation and invasion in vitro and in vivo. Bulk RNA sequencing identified upregulation of genes involved in ferroptosis, which is an iron dependent form of programmed cell death, in STK11/KEAP1 double mutant models, nominating ferroptosis as a potential vulnerability in these tumors. However, the mechanism of ferroptosis evasion in this subset in not well understood.
Methods: We performed an in vitro CRISPR screen in STK11/KEAP1 co-mutant, single mutant and wild type cell lines. To further characterize the role of ferroptosis regulators in STK11/KEAP1 co-mutant setting, we performed phospho-kinase arrays and RNA sequencing in STK11/KEAP1 cell lines followed by validation through western blotting. Additionally, we performed gene expression analysis in patient derived xenografts (PDX) models treated with the SCD inhibitor to further characterize the mechanisms by which SCD inhibition has synthetic lethal effects in STK11/KEAP1 co-mutant background.
Results: CRISPR/Cas9 based genetic screening identified stearoyl-CoA desaturase (SCD), a gene involved in ferroptosis protection, as a potential therapeutic target in the STK11/KEAP1 double mutant tumors. We further demonstrate that SCD overexpression protects STK11/KEAP1 co-mutant NSCLCs from undergoing ferroptosis. Pharmacological inhibition of SCD significantly reduced viability of STK11/KEAP1 co-mutant NSCLCs and made the co-mutant cells sensitive to ferroptosis induction. Phospho-kinase array showed downregulation of JAK-STAT and AKT signaling, in STK11/KEAP1 co-mutant NSCLCs as compared to both STK11 and KEAP1 single mutant isogenic conditions. The downregulation of these pathways was confirmed by gene expression profiling. To further understand the role of SCD in regulating ferroptosis we are studying the effect of concurrent loss of STK11 and KEAP1 on SCD on lipid oxidizing capacity and ferroptosis in a comprehensive panel of NSCLC cell lines and testing whether ferroptosis protection due to SCD overexpression leads to enhanced tumorigenesis in this co-mutant subtype of NSCLC in vivo and in vitro.
Conclusions: Our study demonstrates the biological differences between STK11/KEAP1 co-mutant NSCLC as compared to the single mutants or wildtype counterparts in a KRAS mutation agnostic manner. In this study, we further establish SCD as a potential therapeutic strategy in STK11/KEAP1 co-mutant NSCLCs. We also show that SCD-mediated ferroptosis evasion is linked to multiple oncogenic signaling pathways which could be associated with ferroptosis. In summary we define a new therapeutic approach to STK11/KEAP1 co-mutant NSCLC to improve survival outcomes for patients diagnosed with this devastating disease.
Citation Format: Utsav Sen, Triparna Sen. Targeting Stearoyl-coA desaturase (SCD) as a therapeutic strategy in STK11/KEAP1 co-mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB014.