Elevated ETV6 expression in glioma promotes an aggressive in vitro phenotype associated with shorter patient survival

Purpose It has been postulated that glioblastoma (GBM) has the ability to hijack neural progenitor migration mechanisms to facilitate tumor progression. Our previous data show that ETS variant 6 (ETV6) is highly expressed in human GBM and fetal astrocytes compared to normal mature astrocytes. We hypothesized that ETV6 played a role in GBM tumor progression. Methods Expression of ETV6 was first examined in 2 American and 3 Chinese tissue microarrays. The correlation between ETV6 staining intensity and patient survival was calculated, followed by validation using public databases-TCGA and REMBRANDT. The effect of ETV6 knockdown on glioma cell proliferation (EdU), viability (AnnexinV labeling), clonogenic growth (colony formation), and migration/invasion (transwell assays) in GBM cells was tested. RNA sequencing was performed to ellucidate the underlying molecular mechanisms. Results ETV6 was highly expressed in GBM and associated with an unfavorable prognosis. ETV6 silencing in glioma cells led to increased apoptosis and decreased proliferation, clonogenicity, migration, and invasion. RNA-Seq based gene expression and pathway analyses revealed that ETV6 knockdown in U251 cells led to the upregulation of genes involved in extracellular matrix organization, NF-κB signaling, TNFmediated signaling and downregulation of genes in regulation of cell motility, cell proliferation, PI3KAKT and Ras pathways. Conclusion Our findings suggested that ETV6 was highly expressed in GBM and its high expression correlated with poor survival. ETV6 silencing decreased an aggressive in vitro phenotype. The study encourages further investigation of ETV6 as a potential therapeutic target of GBM. Glioblastoma (GBM) was postulated to have the ability to hijack neural progenitor migration programs to promote tumor progression. Our previous data show that ETS variant 6 (ETV6) is highly expressed in human GBM and fetal astrocytes compared to normal mature astrocytes. We hypothesized a role of ETV6 in GBM tumor progression and investigated it in three aspects. First, the expression of ETV6 was examined in 2 American and 3 Chinese tissue microarrays including totally 192 glioma samples to reveal positive correlation of ETV6 expression with glioma WHO grade and inversed correlation with patient survival. This finding was consolidated by similar correlation in public databases-TCGA and REMBRANDT with totally 1071 glioma samples. Second, the effect of ETV6 knockdown on GBM cellular behaviors such as proliferation, apoptosis, clonogenic growth, migration and invasion was tested in three GBM cell lines. The results showed ETV6 silencing led to increased apoptosis and decreased proliferation, clonogenicity, migration and invasion. At last, RNA-Seq based gene expression and pathway analyses were performed to reveal that the in vitro ETV6-dependent GBM phenotype may partially due to PI3K-AKT and Ras signaling, which is consistent with the effect of ETV6-NTRK3 oncogenic fusion on the two pathways. Our study encourages further investigation of ETV6 as a potential therapeutic target of GBM.