Abstract 2452: Metformin administration in hypoglycemia compromises cancer cell viability in glioblastoma initiating cells

Abstract

Abstract Cancer cells show higher energy and biomolecules requirements than healthy cells, making the targeting of cancer metabolic dysfunctions an appealing therapeutic approach. Unfortunately, tackling the tumor metabolism is a daunting task, due to the ability of cancer cells to re-organize their metabolism switching between glycolysis and oxidative phosphorylation. Cancer metabolic plasticity and re-programming is partially supported by altered ionic channels expression and activity, our laboratory has described Chloride Intracellular Channel 1 (CLIC1) as a marker of malignancy in tumor cells and a possible therapeutic target. CLIC1 is a metamorphic protein able to switch between cytoplasmic and transmembrane forms (tmCLIC1), the latter characterized by chloride conductance. TmCLIC1 was found to be overexpressed in several solid tumors where supports cancer proliferation and growth, while it is mainly absent in healthy cells. Recently, it has been demonstrated that tmCLIC1 activity is affected by biguanide compounds, in particular metformin. Metformin was recently repurposed as an anticancer drug with unclear mechanisms. We demonstrated that in hypoglycemia, metformin displays increased toxic effect on cancer cells, inducing apoptosis. Metformin inhibits Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A), and hypoglycemia upregulates PP2A subunit B56δ targeting the Glycogen Synthase Kinase 3 Beta (GSK3b). Metformin treatment in combination with hypoglycemia leads to de-phosphorylation of GSK3b protein resulting in degradation of induced myeloid leukemia cell differentiation protein (MCL-1), a pro-survival protein, and cell death (Elgendy et al., Cancer Cell 2019). In primary glioblastoma cell lines enriched in tumor-initiating-cells (GSCs), metformin has proven to be effective in reducing cell growth without affecting viability (Gritti et al., Oncotarget 2014). Here, we are going to show studies trying to establish whether CLIC1 is a component of the established PP2A-mediated signaling network. Our work aims to clarify metformin molecular mechanism of action and to assess a new potential therapeutic approach for solid tumors in which tmCLIC1 is found to be overexpressed. Citation Format: Francesca Cianci, Riccardo Cazzoli, Ivan Verduci, Saverio Minucci, Michele Mazzanti. Metformin administration in hypoglycemia compromises cancer cell viability in glioblastoma initiating cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2452.