MiR-1224-5p acts as a tumor suppressor by targeting CREB1 in malignant gliomas.

The dysregulation of miR-1224-5p has been reported in several human cancers. However, the expression and function of miR-1224-5p in glioma remains unknown. The aim of our study was to investigate the effect of miR-1224-5p on glioma cells and to determine its functional signaling mediators. Using 198 glioma samples within the Chinese Glioma Genome Atlas expression dataset, we demonstrated that miR-1224-5p expression is decreased in high-grade gliomas when compared with low-grade gliomas. Differential miR-1224-5p expression in 50 randomly selected samples was verified by in situ hybridization. The expression of miR-1224-5p was shown to positively correlate with overall survival in 82 glioblastoma patients. Exogenous expression of miR-1224-5p in glioma cells suppressed proliferation and invasion and promoted apoptosis. Target prediction algorithms identified a consensus miR-1224-5p recognition site in the 3'UTR of the cAMP response element-binding protein (CREB1) gene, and this sequence was shown to directly confer miR-1224-5p repression in luciferase reporter assays. Furthermore, exogenous miR-1224-5p expression was shown to down-regulate CREB1, as well as its downstream target genes matrix metalloproteinase-9 and B-cell lymphoma-2. Conversely, over-expression of CREB1 reversed the effect of miR-1224-5p on the proliferation, invasion, and apoptosis of glioma cells. These data indicate that miR-1224-5p may inhibit tumor-associated activity in malignant gliomas by targeting CREB1.