Abstract B030: Modulating mitochondria metabolism to radiosensitize KEAP1 mutated non-small cell lung cancer
Authors: Bright Scott J. , Kolachina Rishab , Kacem Mariam Ben , Manandhar Mandira , Jones Philip , Yap Timothy A. , Lin Steven H. , Sawakuchi Gabriel O. 
Published: January 2024

Abstract
Glutamine is the most abundant amino acid in the body. Glutamine is metabolized by the enzyme Glutaminase-1 (GLS1), and results in the formation of glutamate. Glutamate is essential for redox homeostasis, energy production, tricarboxylic acid (TCA) cycle anaplerosis, and synthesis of amino acids, lipids and nucleotides. Genetic alterations in cancer cells like in the protein Kelch-like ECH-associated protein 1 (KEAP1), can rewire cell metabolism creating greater dependency on metabolites such as glutamine. KEAP1-mutant cells rely critically on GLS1 to maintain adequate glutamate levels, TCA cycle fueling and antioxidant production. Notably, 15-20% of non-small cell lung cancers (NSCLC) have mutations in KEAP1. Therefore, GLS1 is a promising target that should show specificity in KEAP1 mutated tumors with relatively limited effects in normal tissue in a significant patient population. GLS1 inhibitors (GLS1i) are being tested in several clinical trials as a monotherapy or in combination. One combination of relevance is radiotherapy (RT)+GLS1i. GLS1 products (lipids, nucleotides, ATP or antioxidants) are heavily implicated in RT response to neutralize radiation-induced reactive oxygen species (ROS) or to serve as substrates to repair radiation-induced DNA damage. Our preliminary data indicate that a novel GLS1 inhibitor (IACS-6274) profoundly sensitizes lung cancer cell lines including KEAP1-mutant and wild type cells exposed to RT+IACS-6274, including proton RT where we saw an increase in the relative biological effectiveness. We also observed significantly more mitochondrial ROS in RT treated groups in the presence of IACS-6274, and that the radiosensitizing effects could be rescued by resupplying cells with α-ketoglutarate, the ROS scavenger N-acetyl cysteine or the ferroptosis inhibitor, ferrostatin 1. Thus, the combination of RT+IACS-6274 may offer a unique treatment combination, that could be further optimized using proton therapy. Maximizing the efficacy of RT+IACS-6274 requires identifying the mechanisms by which GLS1 inhibition sensitizes cells exposed to RT, which are currently unclear. Our findings indicate that radiation induces permanent mitochondria dysfunction, resulting in persistent higher levels of ROS which in turn can be amplified by IACS-6274 treatment. Also, in addition to increased oxidative stress as a result of reduced antioxidants, GLS1 inhibition significantly sensitizes cells to radiation by altering TCA cycle metabolism. In summary, we have identified a patient population (KEAP1 mutated NSCLC) with poorer survival and greater levels of local recurrence that may show profound sensitivity to a novel treatment strategy that exploits tumor metabolic rewiring combined with the unique physical characteristics of RT.
Citation Format: Scott J. Bright, Rishab Kolachina, Mariam Ben Kacem, Mandira Manandhar, Philip Jones, Timothy A. Yap, Steven H. Lin, Gabriel O. Sawakuchi. Modulating mitochondria metabolism to radiosensitize KEAP1 mutated non-small cell lung cancer [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 B030.