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

Glioblastoma (GBM) is the most aggressive and common malignant brain tumor in adults. GBMs are characterized by high intratumor heterogeneity and by the presence of the cancer stem cell niche. The vacuolar ATPase (V-ATPase) is a multisubunit proton pump that plays a role in multiple processes in eukaryotic cells. Altered V-ATPase activity is associated with several human diseases and in cancer may play relevant role due the acidification of cellular organelles, such as, endosomes and lysosomes. We identified overexpression of the V-ATPase V1G1 subunit in GBM derived neurospheres (NS), a cell subpopulation enriched in cancer stem cells. Interestingly GBM NS secrete different types of vesicles, including large oncosomes (LO) thereby influencing their microenvironment. Herein, we assessed the transcriptome of non-sphere forming glioma cells (n=2 pairs) cocultured with LO or empty media (mock) by microarray to identify pathways associated with the LO-induced reprogramming ability. Gene set enrichment analysis (GSEA) revealed that LO-supplemented cultures activated a number of cancer-related pathways, including those involved in glioma V-ATPase-related signaling (Notch, mTOR, and lysosomal transport), as well as cell proliferation and cell transcription programs. Expression data from extracted total RNA of primary human non-sphere-forming glioma cells co-cultured for 6 days with empty medium (mock) or with medium containing LO-High.