TMIC-26. MiR-181a CONTROLS THE OSTEOPONTIN-MEDIATED IMMUNE CIRCUIT IN GLIOBLASTOMA

INTRODUCTION: MiRNAs can silence a broad gene set, which may benefit heterogeneous tumors such as glioblastoma. Osteopontin has been shown to have an oncogenic role in a variety of cancers and may have immune modulatory effects on macrophages. The current study focuses on using miRNAs to target osteopontin in tumor cells and to modulate immune cells to elicit an antitumor effect. METHODS: Genome-wide profiling followed by evaluation of expression levels of miRNAs and osteopontin were measured using quantitative real time PCR and ELISA in mouse and human glioblastoma and macrophages. Luciferase assays were used to determine the binding potential of miRNAs to osteopontin mRNA. miRNA mimics and forced overexpression using lentiviruses were used to target osteopontin in immune competent murine models of glioblastoma. Nano string profiling and Gene Set Enrichment Analysis (GSEA) were conducted to identify differences in biological states. RESULTS: Microarray analysis demonstrated that osteopontin was the most significantly upregulated gene in human glioblastoma-associated infiltrating macrophages that had originated from matched circulating monocytes, and this was validated using qPCR. Based on the 3`UTR sequence of osteopontin, bioinformatics tools identified 5 miRNAs that are conserved and would be able to modulate osteopontin expression. Luciferase assays confirmed that the miR-181 family regulates osteopontin expression. Overexpression of miR-181a in glioblastoma cells led to their decreased proliferation and increased apoptosis in vitro. miR-181a treatment of immune competent mice bearing intracranial glioblastoma demonstrated a 22% increase in median survival time relative to control mice (p=0.006). CONCLUSIONS: miR-181a controls osteopontin expression in both glioblastoma and macrophages by regulating their proliferation and apoptosis.