Spatial Dissection of Invasive Front from Tumor Mass Enables Discovery of Novel microRNA Drivers of Glioblastoma Invasion

Diffuse invasion is the primary cause of treatment failure of glioblastoma (GBM). Previous studies on GBM invasion have long been forced to use the resected tumor mass cells. Here, a strategy to reliably isolate matching pairs of invasive (GBM^INV) and tumor core (GBM^TC) cells from the brains of 6 highly invasive patient-derived orthotopic models is described. Direct comparison of these GBM^INV and GBM^TC cells reveals a significantly elevated invasion capacity in GBM^INV cells, detects 23/768 miRNAs over-expressed in the GBM^INV cells (miRNA^INV) and 22/768 in the GBM^TC cells (miRNA^TC), respectively. Silencing the top 3 miRNAs^INV (miR-126, miR-369-5p, miR-487b) successfully blocks invasion of GBM^INV cells in vitro and in mouse brains. Integrated analysis with mRNA expression identifies miRNA^INV target genes and discovers KCNA1 as the sole common computational target gene of which 3 inhibitors significantly suppress invasion in vitro. Furthermore, in vivo treatment with 4-aminopyridine (4-AP) effectively eliminates GBM invasion and significantly prolongs animal survival times (P = 0.035). The results highlight the power of spatial dissection of functionally accurate GBM^INV and GBM^TC cells in identifying novel drivers of GBM invasion and provide strong rationale to support the use of biologically accurate starting materials in understanding cancer invasion and metastasis.