Endothelin Signaling via EDNRB receptor Reduces Proliferation and Promotes Proneural-to-Mesenchymal Transition in Gliomas

Diffuse gliomas are incurable primary brain tumors encompassing three histo-molecular subtypes: glioblastomas (GB), astrocytomas, and oligodendrogliomas. The latter two harbor IDH1 mutations and exhibit slower progression than glioblastomas. Diffuse gliomas are composed of highly plastic tumor cells capable of transitioning between astrocyte-like, oligodendrocyte-like, progenitor-like, and mesenchymal-like states, driven by genetic alterations and microenvironmental cues. The proneural-to-mesenchymal transition (PMT), associated with increased malignancy, is notably influenced by cytokines in the tumor microenvironment. Endothelin cytokines (ET-1, ET-2, ET-3), primarily secreted by vascular cells, regulate not only vascular tone but also astrocyte and neural stem cell proliferation via the G-protein-coupled receptors EDNRA and EDNRB. Prior studies using serum-cultured glioma lines suggested pro-proliferative effects of endothelins; however, such models poorly recapitulate the in vivo glioma context. In this study, we comprehensively revisited endothelin signaling - covering receptor expression, regulation, downstream pathways, and cellular responses-using eleven serum-free, patient-derived glioma lines (glioblastomas, IDH-wt and IDH-mutant oligodendrogliomas and astrocytomas), along with primary tumor samples. Multi-omics and electrophysiological analyses revealed EDNRB as the predominant receptor, enriched in astrocyte-like cells, upregulated by BMPs or growth factor withdrawal, and downregulated by interferons, IL-6 cytokines, endothelins, and Hippo/YAP activation. In contrast, EDNRA was expressed by a perivascular tumor subpopulation and induced by Notch signaling in glioblastomas but not in IDH1-mutant cells. Functionally, endothelins reduced proliferation across all models while promoting migration and PMT. Mechanistically, EDNRB activation increased intracellular Ca²⁺ and activated ERK, STAT3, and apamin-sensitive SK2/SK3 potassium channels. These findings identify endothelin signaling as an important regulator of glioma cell plasticity and behavior.