Figure 4.

STEAP3 is enriched in the GBM mesenchymal molecular subtype and promotes cell invasive potential. (A) STEAP3 mRNA expression in different molecular subtypes (CpG island methylator phenotype (G-CIMP) proneural, non–G-CIMP proneural, neural, classical, mesenchymal) from the TCGA GBM microarray dataset. (B) GSEA enrichment analysis of mesenchymal and proneural signatures (Verhaak) in STEAP3^highvs STEAP3^low samples in the TCGA GBM dataset. Normalized enrichment score (NES) and FDR are shown for each plot. (C) STEAP3 mRNA expression in neural progenitor cells (n = 3), PN GSCs (n = 18), and MES GSCs (n = 12) in microarray data. (D) Representative images of spheroids in 3D invasion assay for GBM#P3 GSCs transfected with si-Ctrl and si-STEAP3 and evaluated at 0 h and 96 h. The distance of invading cells from the tumor spheres was determined after 96 h. (E) 3D invasion assay at 96 h for GBM#01 GSCs overexpressing STEAP3. (F) Western blot for protein levels of key factors involved in mesenchymal transition in lysates (20 μg) prepared from GBM#P3 and GBM#01 GSCs. GAPDH was used as a loading control. Data are shown as the mean ± SEM from three independent experiments. *P < .05; **P < .01; ***P < .001.