Abstract 703: GABA(A) receptor activation drives GABARAP-Nix mediated autophagy to radiosensitize primary and metastatic lung adenocarcinoma tumors

Abstract In non-small cell lung cancer (NSCLC) treatment, targeted therapies help a subset of patients, and radiotherapy responses are not durable and toxicity limits therapy. Most advanced-stage NSCLC patients have brain metastases that render an abysmal prognosis. Standard-of-care radiation therapy for NSCLC brain metastasis includes stereotactic radiosurgery (SRS) if the number of lesions is less than ten, otherwise whole brain radiation therapy (WBRT) is administered. Challenges in applying radiotherapy include overcoming radiation resistance and reducing significant associated co-morbidities. Cancer neuroscience is an evolving area, and the purpose of this study is to determine if activation of GABA(A) receptors intrinsic to NSCLC cells can improve radiation efficacy in primary NSCLC and its brain metastasis. We find that a GABA(A) receptor activator, AM-101, impairs the viability and clonogenicity of NSCLC primary and brain metastatic cells. Employing a human-relevant ex vivo ‘chip’, AM-101 is as efficacious as docetaxel, a chemotherapeutic used with radiotherapy for advanced-stage NSCLC. In vivo, AM-101 potentiates radiation, including conferring a significant survival benefit to mice bearing NSCLC intracranial tumors generated using a patient-derived metastatic line. GABA(A) receptor activation stimulates a selective-autophagic response via multimerization of GABA(A) Receptor-Associated Protein (GABARAP), stabilization of mitochondrial receptor Nix, utilization of ubiquitin-binding protein p62, and upregulation of Beclin-1. A high-affinity peptide disrupting Nix binding to GABARAP inhibits the cytotoxicity of AM-101. This supports a model of GABA(A) receptor activation driving a GABARAP-Nix multimerization axis that triggers autophagy. In NSCLC brain metastases patients, GABA(A) receptor activation may improve radiation efficacy and tumor control while allowing radiation dose de-intensification to reduce toxicity. Citation Format: Debanjan Bhattacharya, Riccardo Barrile, Donatien Kamdem Toukam, Vaibhavkumar S. Gawali, Laura Kallay, Taukir Ahmed, Hawley Brown, Sepideh Rezvanian, Aniruddha Karve, Pankaj B. Desai, Mario Medvedovic, Kyle Wang, Dan Ionascu, Nusrat Harun, Chenran Wang, Andrew M. Baschnagel, Joshua A. Kritzer, James Cook, Daniel A. Pomeranz Krummel, Soma Sengupta. GABA(A) receptor activation drives GABARAP-Nix mediated autophagy to radiosensitize primary and metastatic lung adenocarcinoma tumors [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(6_Suppl):Abstract nr 703.