Glioblastoma can originate from terminally differentiated astrocytes and neurons, which can dedifferentiate to a stem cell-like state upon transformation.
In this study, researchers at UCSD confirmed that transformed dedifferentiated astrocytes and neurons acquired a stem/progenitor cell state, although they still retained gene expression memory from their parental cell.
Scheme of experimental design. (a) mRNA collected from enriched populations of mESCs, NSCs, primary cultures of cortical neurons and astrocytes, and dedifferentiated neurons and astrocytes were subjected to sequencing library generation using DP-seq. Dedifferentiation of neurons and astrocytes was achieved by transducing the primary cultures of neuron and astrocytes by lentiviral vector comprising of HRas and shp53. The transduced neurons and astrocytes were switched to stem cell media devoid of serum and supplemented with FGF-2 for 3 weeks. (b) Differential expression of NSC markers and differentiation specific markers in dedifferentiated cell types in comparison with their mature parental cell types. (c) Pathway enrichment. The genes commonly upregulated in the dedifferentiated cell types showed enrichment for Wnt signaling, cell cycle and focal adhesion pathways. (d) Single sample gene set enrichment analysis. Gene lists comprising of the known markers (number of genes in the parentheses) showed significant enrichment in the respective populations. The dedifferentiated cell types exhibited high enrichment scores for NSC markers, neuron markers and a distinct set of focal adhesion genes.
Transcriptional network analysis on these cells identified upregulated genes in three main pathways: Wnt signaling, cell cycle and focal adhesion with the gene Spp1, also known as osteopontin (OPN) serving as a key common node connecting these three pathways. Inhibition of OPN blocked the formation of neurospheres, affected the proliferative capacity of transformed neurons and reduced the expression levels of neural stem cell markers. Specific inhibition of OPN in both murine and human glioma tumors prolonged mice survival. The researchers conclude that OPN is an important player in dedifferentiation of cells during tumor formation, hence its inhibition can be a therapeutic target for glioblastoma.
Gene/protein interaction network of differentially expressed genes in NSynR53 in comparison with neurons. An interaction network was constructed from publicly available databases comprising of protein–protein interactions (KEGG, STRING, BioGRID) and genetic interactions (TRANSFAC). The differentially expressed genes were projected into this network that revealed a module showing association of genes related to the focal adhesion, cell cycle and the Wnt signaling pathways. The edges represent the interactions observed in various databases.