Abstract LB-245: MicroRNA-100 targets silencing mediator for retinoid receptors (SMRT), reduces proliferation, and improves survival in glioblastoma.

Abstract

Abstract Improved therapeutic approaches are needed for the most common primary adult brain cancer, Glioblastoma (GBM) because of the current dismal median survival of less than two years. We identified and tested the differentially expressed microRNA-100 (MiR-100) as a candidate ‘tumor suppressor’ in GBM. Quantitative PCR validated differential microRNA array results showing high miR-100 expression in normal cells and low expression in multiple GBM lines. MiR-100 overexpression via transfection of 4 GBM lines with miR-100 precursor (U87, U251, patient-derived 22T and 33T) reduced proliferation on MTS assays (average 50% ± 15; p < 0.05). TUNEL assays showed that transient transfection of 15 pmole of miR-100 per 500K GBM tumor cells triggered apoptosis 70% more than scrambled control miR after 24 hrs (p < 0.01). SMRT was identified as a candidate miR100 target in multiple miRNA databases, and validated with miR100-specific inhibition in a luciferase-SMRT 3′UTR reporter assay. In addition, a single dose of pre-mir-100 (60 pmol) injected directly into intracranial GBM xenografts significantly extended survival 30% more than mice injected with control scrambled miRNA (p < 0.01; n=8). GBM lines that stably overexpressed miR-100 two-fold over similar control transfected GBM lines were created for in vivo studies: 10x6 cells were implanted for tumor xenograft histology and survival analysis. Significantly reduced Ki-67 proliferation index was observed compared to control (mir-100 vector: 18±14% Ki-67+; empty vector: 100±11% Ki-67+; p < 0.01). Two-fold over-expression of miR-100 in vivo showed an average of 70% reduction in Ki-67 proliferation index. Furthermore, miR-100 overexpressing cells were associated with significantly smaller xenografts than injection of sibling control GBM cells. These studies establish the ‘tumor suppressor’ activity of miR-100 in GBM, which may lead to further developments as novel GBM therapies. Citation Format: Bahauddeen M. Alrfaei, Raghu Vemuganti, John S. Kuo. MicroRNA-100 targets silencing mediator for retinoid receptors (SMRT), reduces proliferation, and improves survival in glioblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-245. doi:10.1158/1538-7445.AM2013-LB-245