MicroRNA-378 enhances radiation response in ectopic and orthotopic implantation models of glioblastoma

Glioblastoma multiforme (GBM) is the most common and highly malignant primary brain tumor, which is virtually incurable due to its therapeutic resistance to radiation and chemotherapy. To develop novel therapeutic approaches for treatment of GBM, we examined the role of on tumor growth, angiogenesis, and radiation response in ectopic and orthotopic U87 glioblastoma miR-378 models. Cell and tumor growth rates, in vitro and in vivo radiation sensitivities, and tumor vascular density were evaluated in U87-GFP and U87- radiation was evaluated under normal blood flow and clamp hypoxic conditions. Results show that miR-378 miR-378 tumor lines. Ectopic tumor response to in vitro, expression moderately increased cell growth rate and plating efficiency, but did not alter radiation sensitivity. U87- tumors exhibited a higher transplantation take rate than U87-GFP tumors. In vivo, under oxygenated condition, subcutaneous U87- miR-378 tumors receiving 25 Gy showed a tendency for longer tumor growth delay (TGD) than control U87-GFP tumors. In contrast, under hypoxic condition, U87- miR-378 shorter TGD than U87-GFP tumors, indicating that under normal blood flow conditions, U87- miR-378 miR-378 xenografts exhibited substantially tumors were substantially more oxygenated than U87-GFP tumors. Intracranial multi- photon laser-scanning microscopy demonstrated increased vascular density of U87- versus control U87-GFP tumors. Finally, increased TGD following 12 Gy irradiation in miR-378 U87 intracranial xenografts, and significantly prolonged survival of U87- miR-378 tumor-bearing mice ( P = 0.04). In conclusion, higher miR-378 expression in U87- miR-378 miR-378 cells promotes tumor growth, angiogenesis, radiation-induced TGD, and prolongs survival of orthotopic tumor-bearing hosts. Regulation of VEGFR2 by miR-378 significantly increased vascular density and oxygenation in U87 xenografts.