miR-34a confers chemosensitivity through modulation of MAGE-A and p53 in medulloblastoma

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2011-02, Vol.13 (2), p.165-175
• Main Authors: Weeraratne, Shyamal D., Amani, Vladimir, Neiss, Adrianne, Teider, Natalia, Scott, Deborah K., Pomeroy, Scott L., Cho, Yoon-Jae
• Format: Article
• Language: English
• Subjects: Antigens, Neoplasm - genetics; Antigens, Neoplasm - metabolism; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Basic and Translational Investigations; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Blotting, Western; Cell Cycle - drug effects; Cell Proliferation - drug effects; Cerebellar Neoplasms - drug therapy; Cerebellar Neoplasms - metabolism; Cerebellar Neoplasms - pathology; Cisplatin - pharmacology; Drug Resistance, Neoplasm - genetics; Gene Expression Profiling; Humans; Immunoenzyme Techniques; Luciferases - metabolism; Medulloblastoma - drug therapy; Medulloblastoma - metabolism; Medulloblastoma - pathology; Melanoma-Specific Antigens; MicroRNAs - physiology; Mitomycin - pharmacology; Neoplasm Proteins - antagonists & inhibitors; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Oligonucleotide Array Sequence Analysis; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Small Interfering - genetics; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noq179

Recent studies have established miR-34a as a key effector of the p53 signaling pathway and have implicated its role in multiple cancer types. Here, we establish that miR-34a induces apoptosis, G2 arrest, and senescence in medulloblastoma and renders these cells more sensitive to chemotherapeutic agents. These effects are mediated in part by the direct post-transcriptional repression of the oncogenic MAGE-A gene family. We demonstrate that miR-34a directly targets the 3′ untranslated regions of MAGE-A genes and decreases MAGE-A protein levels. This decrease in MAGE-A results in a concomitant increase in p53 and its associated transcriptional targets, p21/WAF1/CIP1 and, importantly, miR-34a. This establishes a positive feedback mechanism where miR-34a is not only induced by p53 but increases p53 mRNA and protein levels through the modulation of MAGE-A genes. Additionally, the forced expression of miR-34a or the knockdown of MAGE-A genes by small interfering RNA similarly sensitizes medulloblastoma cells to several classes of chemotherapeutic agents, including mitomycin C and cisplatin. Finally, the analysis of mRNA and micro-RNA transcriptional profiles of a series of primary medulloblastomas identifies a subset of tumors with low miR-34a expression and correspondingly high MAGE-A expression, suggesting the coordinate regulation of these genes. Our work establishes a role for miR-34a in modulating responsiveness to chemotherapy in medulloblastoma and presents a novel positive feedback mechanism involving miR-34a and p53, via direct targeting of MAGE-A.