Abstract 4284: Targeting notch signaling in glioblastoma cancer stem cells through modulation of Connexin43 function

Abstract

Abstract Glioblastoma (GBM) is a highly malignant and lethal cancer of the central nervous system for which there has been limited progress in improving patient outcomes despite intensive research efforts. The current multimodal therapy for newly diagnosed GBM patients includes surgical resection, radiotherapy and cytotoxic chemotherapy with temozolomide (TMZ), conferring a median survival time of just 14.6 months. Failure to generate more effective treatment strategies is due to 1) the infiltrative nature of GBM tumor cells preventing complete surgical resection, and 2) the cellular heterogeneity within GBM tumors, which often comprise a sub-population of GBM cancer stem cells (GSCs) characterized by self-renewal characteristics and resistance to chemotherapeutic alkylating agents including TMZ. Multiple signaling pathways, including Notch, participate to the formation and maintenance of GSCs. Recent studies, including our research, have shown that increased levels of gap junction protein Connexin43 (Cx43) correlate with TMZ resistance in GBM cells and inversely correlated with GBM patient survival. Importantly, Cx43 has also been associated with anti-proliferative effects in glioma, and reduced levels of Cx43 protein occur in high-grade gliomas. Therefore, we hypothesized that altering Cx43 localization and/or activity rather than Cx43 expression represents a potent strategy for GBM treatment. Regulating Cx43 function is primarily associated with the multiple sites for post-translational modifications and protein-protein interactions within the Cx43 carboxy-terminus. Our research identifies crosstalk between Cx43 and Notch signaling in GSCs. Using a Cx43 carboxy-terminus mimetic peptide that modulates non-junctional functions of Cx43, we observe a decrease in Notch1 protein expression and reduced transcription of its downstream targets Hes1 and Hey1 in GSCs derived from patient tumors. Most importantly, our Cx43 mimetic peptide decreases cell survival in TMZ-resistant GSCs, limits GSC neurosphere formation in vitro, and inhibits GSC-derived tumor growth in vivo. Our current research aims at dissecting the molecular mechanisms of Cx43 functions on Notch signaling in GSCs using this Cx43 mimetic peptide. In conclusion, we have identified a novel therapeutic opportunity to decrease the tumorigenic potential of GSCs through altering Cx43 activity and Notch signaling to target chemoresistant GSCs in GBM treatment. Citation Format: Michael Lunski, James Smyth, Jennifer Vaughn, Zhi Sheng, Robert Gourdie, Benjamin Purow, Samy Lamouille. Targeting notch signaling in glioblastoma cancer stem cells through modulation of Connexin43 function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4284.