RNA-seq changes in glioblastoma-derived extracellular vesicle cargos of patient-derived xenograft models as a pharmacodynamic reporter
Glioblastoma (GBM) is the most aggressive tumor and lethal disease of the central nervous system. Gliomas have a poor prognosis, as delayed diagnosis is common and standard treatment approaches are unable to cope with the tumor’s heterogeneity, mutagenesis and invasiveness. The purpose of this study is to explore the potential of liquid biopsy approaches to determine whether a drug has crossed the blood brain barrier and reached the tumor. This would be transformative as a minimally invasive alternative to the existing invasive option of a tumor biopsy. Previous studies have identified extracellular vesicles (EVs) as an integral part of tumor growth and resistance, and because EVs reflect the cell identity and functional state of the parental cells from which they are derived, we propose that they may be a possible pharmacodynamic reporter. To look at drug-dependent changes, four GBM patient derived xenografts were grown as short-term cultures, treated with arsenic trioxide, the NEDD8-activating enzyme inhibitor MLN4924, temozolomide or vehicle; EVs were then isolated and RNA was extracted and sequenced. Sequence data revealed condition-dependent alterations in the RNA cargos of glioma-derived EVs. Two genes were found to be consistently downregulated across all drug-treatment conditions in GBM10, GBM120, and GBM43. Many differentially expressed genes observed to be commonly upregulated were found to be long non-coding RNA with possible regulatory influence on oncogenes. Through gene set enrichment analyses, differentially expressed genes belonged to biological processes including sensory pathways, cell division, regulation, and cancer pathways. Altogether, this data suggests that RNA cargo reflects interaction between drug and GBM tumor cells, supporting the potential utility of plasma EVs as a liquid biopsy to determine blood brain barrier penetrance.