Introduction: To examine the molecular mechanism by which miRNA-16 (miR-16) suppresses glioblastoma in vitro and in vivo.
Methods: Gene expression of miR-16 in normal brain tissues and human glioma cell lines was examined. To characterize the functional role of miR-16 in vitro, miR-16 was ectopically expressed in U87 cells by lentiviral transduction. Expression of miR-16 downstream targets cyclin D1 and Bcl-2 in U87 was studied using Western blotting. Cell proliferation and clonogenic property were examined using CCK-8 and clone formation assay, respectively. Migration and invasiveness of U87 was studied using wound-healing assay and transwell assay, respectively. In vivo tumorigenic properties of the miR-16-transduced U87 cells were examined in an orthotopic xenograft model. Immunohistochemistry was performed to examine cyclin D1, WIP1 and CD31 expressions.
Results: Expression of miR-16 was reduced in glioblastoma cell lines compared to normal human brain tissues. Ectopic miR-16 expression reduced cyclin D1 and Bcl-2 in U87 cells. miR-16 also induced apoptosis, reduced cell proliferation and clone formation. Furthermore, miR-16 suppressed U87 migration in wound-healing assay and invasion across transwell membrane in vitro. In an orthotopic tumor model, overexpression of miR-16 inhibited tumor growth in vivo was accompanied with reduction in cyclin D1 and WIP1 expression in the xenografts. CD31 expression in miR-16-overexpressed xenografts was also decreased. The determined microvessel density of the miR-16 overexpression group was significantly lower than those groups treated with vehicle and empty vector.
Discussion: MicroRNA-16 exhibits inhibitory effects of glioblastoma. MicroRNA-16 and its downstream targets could be potential therapeutic targets for treatment of glioblastoma.
Keywords: microRNA-16, glioblastoma, cyclin D1, WIP1, angiogenesis, apoptosis, invasion