The vacuolar H+ ATPase is a novel therapeutic target for glioblastoma.

Andrea Di Cristofori,Mario Zavanone,Paolo Rampini,Stefano Ferrero,Valentina Vaira,Gabriella Gaudioso,Maria Veronica Russo,Thomas Vaccari,Marco Vanini,Valeria Berno,Irene Bertolini,Marco Locatelli,Manuela Caroli

doi:10.18632/oncotarget.4239

Abstract

The vacuolar H+ ATPase (V-ATPase) is a proton pump responsible for acidification of cellular microenvironments, an activity exploited by tumors to survive, proliferate and resist to therapy. Despite few observations, the role of V-ATPase in human tumorigenesis remains unclear.We investigated the expression of ATP6V0C, ATP6V0A2, encoding two subunits belonging to the V-ATPase V0 sector and ATP6V1C, ATP6V1G1, ATPT6V1G2, ATP6V1G3, which are part of the V1 sector, in series of adult gliomas and in cancer stem cell-enriched neurospheres isolated from glioblastoma (GBM) patients. ATP6V1G1 expression resulted significantly upregulated in tissues of patients with GBM and correlated with shorter patients' overall survival independent of clinical variables.ATP6V1G1 knockdown in GBM neurospheres hampered sphere-forming ability, induced cell death, and decreased matrix invasion, a phenotype not observed in GBM monolayer cultures. Treating GBM organotypic cultures or neurospheres with the selective V-ATPase inhibitor bafilomycin A1 reproduced the effects of ATP6V1G1 siRNA and strongly suppressed expression of the stem cell markers Nestin, CD133 and transcription factors SALL2 and POU3F2 in neurospheres.These data point to ATP6V1G1 as a novel marker of poor prognosis in GBM patients and identify V-ATPase inhibition as an innovative therapeutic strategy for GBM.

Highlights

V-ATPase is a ubiquitously expressed and evolutionary conserved multimeric proton pump that acidifies intracellular compartments and the extracellular milieu
In this study we show that V-ATPase G1 is a novel marker of poor prognosis for glioblastoma patients
V-ATPase G1 levels were predictive of overall survival in GBM patients independently of the epigenetic silencing of methylguanine-DNA methyltransferase (MGMT) gene, isocitrate dehydrogenase 1 (IDH1) mutation, Karnofsky performance score, or patients’ age at diagnosis

Summary

Introduction

V-ATPase is a ubiquitously expressed and evolutionary conserved multimeric proton pump that acidifies intracellular compartments and the extracellular milieu. ATPase activity with V0 rotation [1]. Recent evidence indicated that V-ATPase acts directly in the endolysosomal compartment to modulate signaling pathways important for development that are dysregulated in cancer, such as Notch, Wnt or mTOR signaling [37]. This evidence, together with the fact that a variety of human tumors display overexpression of V-ATPase subunits, suggests that V-ATPase might play a crucial, albeit largely unexplored, role in supporting tumorigenesis. V-ATPase could in principle represent a novel target for anti-neoplastic approaches [13,14,15,16]

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