Despite recent improvements in the overall survival of medulloblastoma (MB), only a modest percentage of patients survive high-risk disease. Furthermore, the toxicity associated with current therapies inflicts debilitating lifelong side effects on surviving MB patients. Using an unbiased microRNA screen, we identified miR-584-5p as a potent tumor suppressor that uniquely sensitizes MB to both ionizing radiation (IR) and vincristine (VCR), which are commonly used in combination to treat MB. Our studies revealed that miR-584-5p inhibited MB stem cell proliferation and consequently growth in vivo. Notably, we discovered that miR-584-5p imparts its tumor-suppressor and therapy-sensitizing effects by inhibiting histone deacetylase 1 (HDAC1), eukaryotic translation initiation factor 4e family member 3 (eIF4E3), and C-MYC. We demonstrated that miR-584-5p overexpression or the knockdown of its target genes including eIF4E3 and HDAC1 resulted in G2-M arrest, DNA damage, spindle defects, and apoptosis in MB cells. Meta-analysis of normal brain and MB tumor samples showed that while miR-584-5p is highly expressed in normal brain and cerebellum, it is highly downregulated across all MB subtypes. miR-584-5p targets, on the other hand, are highly overexpressed in MB tumors compared to normal cerebellum. Taken together, this study highlights a previously unidentified role for miR-584-5p, eIF4E3, and HDAC1 in regulating microtubule dynamics and DNA repair pathways. In addition, our study identifies novel targets that can affect the therapeutic efficacy of VCR and IR in MB and sets the stage for a new paradigm of treating medulloblastoma using microRNA-based therapeutics.

Citation Format: Nourhan Abdelfattah, Subapriya Rajamanickam, Santosh Timilsina, Panneerdoss Subbarayalu, Benjamin Onyeagucha, Manjeet Rao. Tumor suppressor miR-584-5p regulates MYC and sensitizes MYC-amplified medulloblastoma to vincristine and ionizing radiation [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A45.