A GBM-like V-ATPase signature directs cell-cell tumor signaling and reprogramming via large oncosomes

Abstract

Background The V-ATPase proton pump controls acidification of intra and extra-cellular milieu in both physiological and pathological conditions. We previously showed that some V-ATPase subunits are enriched in glioma stem cells and in patients with poor survival. In this study, we investigated how expression of a GBM-like V-ATPase pump influences the non-neoplastic brain microenvironment. Methods Large oncosome (LO) vesicles were isolated from primary glioblastoma (GBM) neurospheres, or from patient sera, and co-cultured with primary neoplastic or non-neoplastic brain cells. LO transcript and protein contents were analyzed by qPCR, immunoblotting and immunogold staining. Activation of pathways in recipient cells was determined at gene and protein expression levels. V-ATPase activity was impaired by Bafilomycin A1 or gene silencing. Findings GBM neurospheres influence their non-neoplastic microenvironment by delivering the V-ATPase subunit V1G1 and the homeobox genes HOXA7, HOXA10, and POU3F2 to recipient cells via LO. LOs reprogram recipient cells to proliferate, grow as spheres and to migrate. Moreover, LOs are particularly abundant in the circulation of GBM patients with short survival time. Finally, impairment of V-ATPase reduces LOs activity. Interpretation We identified a novel mechanism adopted by glioma stem cells to promote disease progression via LO-mediated reprogramming of their microenvironment. Our data provide preliminary evidence for future development of LO-based liquid biopsies and suggest a novel potential strategy to contrast glioma progression. Fund This work was supported by Fondazione Cariplo (2014-1148 to VV) and by the Italian Minister of Health-Ricerca Corrente program 2017 (to SF).

Extracellular Vesicle-Dependent Cross-Talk in Cancer—Focus on Pancreatic Cancer

“…Practically, most studies are focused on EVs that measure 1 µm or less, corresponding mostly to exosomes. To date, few articles are based on microvesicles larger than 1 µm like large oncosome (16)(17)(18)(19). In 2014, The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles ("MISEV") guidelines for EV isolation and purification.…”

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“…Among these nanovesicles, atypically large extracellular vesicles (0.5-5 µm in diameter) referred to as large oncosomes (LOs) have been identified. LOs can be byproducts of non-apoptotic cells when a large portion of the cellular membrane is shedding from the outward membrane during blebbing events [83]. The shedding process is induced by silencing of the cytoskeletal regulator DIAPH3 (Diaphanous-related formin-3) protein, by the overexpression of oncoproteins (Cav-1 (caveolin-1), HB-EGF (heparin-binding epidermal growth factor), MyrAkt1 (myristoylated Akt1)), or activation of the EGFR and AKT1 pathways [24,[84][85][86][87].…”

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“…Terrasi and coworkers suggested that V-ATPase subunits signature that accompanies glioma of different grade may be an independent prognostic marker of IDH wild-type low-grade glioma [ 46 ]. V1G1 subunit of V-ATPase is in many cases overexpressed in glioblastoma cells and is associated with shorter patient survival, moreover in peripheral blood of patients with glioblastoma were detected large oncosomes, a type of extracellular vesicle, that highly express V-ATPase.…”

“…V1G1 subunit of V-ATPase is in many cases overexpressed in glioblastoma cells and is associated with shorter patient survival, moreover in peripheral blood of patients with glioblastoma were detected large oncosomes, a type of extracellular vesicle, that highly express V-ATPase. Authors supposed that those oncosomes could be useful as liquid biopsy [ 46 ]. Recent in silico study shows, that expression pattern of V-ATPase (combinations in up- and downregulation in the expression ratios of V-ATPase subunits and isoforms) is distinct in different cancers (leukemia, lymphoma, melanoma, myeloma, sarcoma, bladder, brain, breast, cervical, colorectal, esophageal, gastric, head and neck, kidney, liver, lung, ovarian, pancreatic, and prostate cancer) [ 47 ].…”