Specific V-ATPase expression sub-classifies IDHwt lower-grade gliomas and impacts glioma growth in vivo

Abstract

Background Cancer cells use specific V-ATPase subunits to activate oncogenic pathways. Therefore, we investigated V-ATPase deregulation in aggressive gliomas and associated signaling. Methods V-ATPase genes expression and associated pathways were analyzed in different series of glioma available from public databases, as well as in patients' cohort. Activation of pathways was analyzed at gene and protein expression levels. A genetic model of glioma in Drosophila melanogaster and mice with GBM patients-derived orthotopic xenografts were used as in vivo models of disease. Findings GBM and recurrent gliomas display a specific V-ATPase signature. Such signature resolves the heterogeneous class of IDH-wild type lower-grade gliomas, identifying the patients with worse prognosis independently from clinical and molecular features (p = 0·03, by Cox proportional-hazards model). In vivo , V-ATPase subunits deregulation significantly impacts tumor growth and proliferation. At the molecular level, GBM-like V-ATPase expression correlates with upregulation of Homeobox genes. Interpretation Our data identify a V-ATPase signature that accompanies glioma aggressiveness and suggest new entry points for glioma stratification and follow-up. Fund This work was supported by Fondazione Cariplo (2014–1148 to VV), Fondazione IRCCS Ca' Granda, and Fondazione INGM Grant in Molecular Medicine 2014 (to VV).

V-ATPase controls tumor growth and autophagy in aDrosophilamodel of gliomagenesis

“…In contrast to Mitf downregulation, glial-specific downregulation of the V-ATPase subunit VhaPPA1-1 in the context of Drosophila gliomagenesis (gliomas>VhaPPA1-1 RNAi ) strongly prevents glial cell overgrowth ( Fig. 3A; S3A; [11]). In fact, glia-associated GFP expression as well as CNS size are significantly decreased by VhaPPA1-1 subunit downregulation (Fig.…”

“…Our fly model recaptures aspects of human glioblastoma, including the following evidence obtained with mammalian models and patient samples: Elevated expression of V-ATPase subunits [10], [39]; Induction of autophagy by AKT inhibitors in glioma cells [40]; Proliferation arrest induced by PI3K/mTOR dual inhibitors [41]; Reduction of tumor growth and induction of autophagy by downregulation of the PI3K-AKT-mTOR pathway [42]. Thus, we predict that future study of fly gliomas could provide a framework to uncover new genetic vulnerabilities in GBM.…”

“…A recently discovered prognostic feature of GBM is expression of subunits of the V-ATPase proton pump, which are frequently found upregulated in cancer [8], [9]. In fact, in GBM tissue samples and GBM patient-derived neurospheres (NS), increased expression of a subset of V-ATPase subunits positively correlates with GBM aggressiveness and poor patient survival [10], [11].…”

“…Secondary antibodies used were rabbit, mouse, rat and chicken HRPconjugated 1:8000 (Amersham). Protein extraction from NS was performed as in[11]. We used the following primary antibodies: Mouse anti-Vinculin 1:1000 (V4505, Sigma Aldrich), rabbit anti-p-ERK 1/2 (Thr202/Tyr204) 1:1000 (4370, Cell Signaling), rabbit anti-ERK 1/2 1:1000 (4695, Cell Signaling).…”

Reprogramming of GBM microenvironment by large oncosomes: ‘Traveling’ V-ATPases are doing more than acidification

“…On the clinical side, Bertolini et al were able to demonstrate that the detection of ATP6V1G1 and homeobox genes in LOs isolated from blood of GBM patients could become a powerful diagnostic tool to classify glioma stages, as further detailed in a companion paper published in the same issue [8]. On the other hand, this study highlights the relevance of developing new therapeutic strategies based on the targeting of V-ATPases, while taking advantage of the inhibitors already used in clinics.…”