Abstract 791: V-ATPase in glioma stem cells: V1G1 subunit expression correlates with metabolic behavior and mitochondria activity

Abstract

Abstract Background The vacuolar H+-ATPase (V-ATPase) is a multisubunit proton pump with a role in the acidification of the extra- and intra-cellular environments. Recent evidence connected V-ATPase deregulation and human diseases, including cancer. We previously demonstrated that the overexpression of the catalytic subunit V1G1 is correlated with glioma stem cells (GSC) maintenance. According to V1G1 expression, we sorted glioblastoma patients-derived neurospheres cultures (NS) into two categories: V1G1HIGH and V1G1LOW NS. These NS differ in terms of stem cell genes expression, sphere formation, invasion ability, lysosomal acidity and bioenergetics. Methods V1G1HIGH, V1G1LOW NS treated with 10nM of BafilomycinA1 (BafA1) or vehicle for 24h (n=3 per group) were used for the functional experiments. Lactate, glucose, ATP levels were measured by commercial kits. Metabolic proteins expression was assessed by western blot. ROS production and mitochondria function were measured by flow cytometry using MitoSox and TMRE assays, respectively. Results At basal conditions, V1G1LOW NS produce higher levels of lactate (p=0.0379) whereas V1G1HIGH NS show higher levels of extracellular glucose and intracellular ATP. Accordingly, the two NS cultures show an opposite trend in LDH subunits expression with LDHA, which pushes lactate production, being more expressed in V1G1LOW (p=0.0027). Conversely, LDHB that facilities the production of pyruvate from lactate, and the transporter MCT1 are more expressed in V1G1HIGH NS. Interestingly, using the V-ATPase specific inhibitor BafA1, metabolic characteristics of V1G1HIGH are redirected to the V1G1LOW phenotype. Moreover, in V1G1HIGH NS BafA1 induces ROS production and affects mitochondria activity, increasing their depolarization. Conclusions Taken together these data suggest two distinct metabolic behaviors of NS according to V-ATPase expression. Indeed for energy production V1G1LOW NS could rely on a glycolytic metabolism whereas V1G1HIGH NS on oxidative phosphorylation. Moreover, when overexpressed the proton pump could also have a role in preserving mitochondria polarity. Although preliminary, this is the first evidence reporting a role for V-ATPase in the regulation of cancer stem cell metabolism. Citation Format: Alessandra M. Storaci, Irene Bertolini, Manuela Caroli, Stefano Ferrero, Valentina Vaira. V-ATPase in glioma stem cells: V1G1 subunit expression correlates with metabolic behavior and mitochondria activity [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 791.