Abstract 3162: Antagonizing beta-2 adrenergic receptor’s function triggers death in glioma cells and down-regulates survivin
Authors: Algranatti Orli , Lee Ji Yae , Angelastro James M. 
Published: March 2024

Abstract
Introduction: Epidemiological studies showed that beta-adrenergic antagonists caused a low incidence of several cancer types. Glioblastoma highly expresses beta-2-adrenergic receptors. GBM accounts for 50% of central nervous system cancers. After standard-of-care therapeutic intervention, there is a survival time of 15 months. Our goal is to develop a translational therapy that will trigger the death of GBM cells while preserving healthy cells
Methodology: Salmeterol xinafoate is a biased agonist that activates the G-protein pathway. Biased agonists activate signaling through the G-protein or the beta-arrestin pathway of G-protein coupled receptors. Dose-response experiments were performed using beta1 and beta2-adrenergic receptor antagonists and biased beta2-adrenergic receptor agonists to determine loss of glioma cell viability in GBM5, GBM12, and LN229 glioma cell lines. Western immunoblotting gauged survivin expression levels in all three lines. Epoxomicin was used to inhibit the proteasome complex. Annexin V and propidium iodide were employed to measure apoptotic or necrotic cell death.
Results: Disrupting beta2-adrenergic receptor signaling by salmeterol xinafoate led to cell death of glioma cells but spared healthy neuron-glia cells using similar doses. Salmeterol xinafoate revealed greater efficacy for killing glioma cells than beta1 and beta2-adrenergic receptor antagonists. To determine the mechanism of glioma cell death, LN229 cells were treated with escalating doses of Salmeterol xinafoate, and at 24 hours, annexin V staining showed early apoptosis, and Annexin V/propidium iodide co-staining also showed late apoptosis. Propidium iodide revealed minor necrosis in LN229 glioma cells. Western immunoblotting showed salmeterol xinafoate downregulated survivin in a dose-dependent manner. However, the epoxomicin's inhibition of the proteasome complex prevented dose-escalated downregulation of survivin for all three glioma cell lines.
Conclusion: The bitopic structure of salmeterol enables this drug to bind to the beta2-adrenergic receptors ligand binding site and an exosite site by its aryloxyalkyl tail that may contribute to the increased efficacy. Salmeterol xinafoate triggers glioma cell death by apoptosis at least in one glioma cell line. Salmeterol Xinafoate down-regulates survivin through protease degradation. Promising results show that the FDA-approved drug salmeterol xinafoate enables a favorable transition to the clinic. Repurposing this drug for GBMs may be combined with the current standard-of-care chemotherapies to enhance more significant loss of tumor volume and increase patient survival.
Citation Format: Orli Algranatti, Ji Yae Lee, James M. Angelastro. Antagonizing beta-2 adrenergic receptor’s function triggers death in glioma cells and down-regulates survivin [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 3162.