Prion protein regulates invasiveness in glioblastoma stem cells

Background: Glioblastoma (GBM) is an aggressive brain tumor driven by glioblastoma stem cells (GSCs), which represent an appealing target for therapeutic interventions. The cellular prion protein (PrP^C), a scaffold protein involved in diverse cellular processes, interacts with various membrane and extracellular matrix molecules, influencing tumor biology. Herein, we investigate the impact of PrP^C expression on GBM.

Methods: To address this goal, we employed CRISPR-Cas9 technology to generate PrP^C knockout (KO) glioblastoma cell lines, enabling detailed loss-of-function studies. Bulk RNA sequencing followed by differentially expressed gene and pathway enrichment analyses between U87 or U251 PrP^C-wild-type (WT) cells and PrP^C-knockout (KO) cells were used to identify pathways regulated by PrP^C. Immunofluorescence assays were used to evaluate cellular morphology and protein distribution. For assessment of protein levels, Western blot and flow cytometry assays were employed. Transwell and growth curve assays were used to determine the impact of loss-of-PrP^C in GBM invasiveness and proliferation, respectively. Single-cell RNA sequencing analysis of data from patient tumors from The Cancer Genome Atlas (TCGA) and the Broad Institute of Single-Cell Data Portal were used to evaluate the correspondence between our in vitro results and patient samples.

Results: Transcriptome analysis of PrP^C-KO GBM cell lines revealed altered expression of genes associated with crucial tumor progression pathways, including migration, proliferation, and stemness. These findings were corroborated by assays that revealed impaired invasion, migration, proliferation, and self-renewal in PrP^C-KO GBM cells, highlighting its critical role in sustaining tumor growth. Notably, loss-of-PrP^C disrupted the expression and localization of key stemness markers, particularly CD44. Additionally, the modulation of PrP^C levels through CD44 overexpression further emphasizes their regulatory role in these processes.

Conclusions: These findings establish PrP^C as a modulator of essential molecules on the cell surface of GSCs, highlighting its potential as a therapeutic target for GBM.