Abstract
Radiation is a core part of therapy for malignant glioma and is often provided following debulking surgery. However, resistance to radiation occurs in most patients, and the underlying molecular mechanisms of radio-resistance are not fully understood. Here, we demonstrated that microRNA 21 (miR-21), a well-known onco-microRNA in malignant glioma, is one of the major players in radio-resistance. Radio-resistance in different malignant glioma cell lines measured by cytotoxic cell survival assay was closely associated with miR-21 expression level. Blocking miR-21 with anti-miR-21 resulted in radio-sensitization of U373 and U87 cells, whereas overexpression of miR-21 lead to a decrease in radio-sensitivity of LN18 and LN428 cells. Anti-miR-21 sustained γ-H2AX DNA foci formation, which is an indicator of double-strand DNA damage, up to 24 hours and suppressed phospho-Akt (ser473) expression after exposure to γ-irradiation. In a cell cycle analysis, a significant increase in the G₂/M phase transition by anti-miR-21 was observed at 48 hours after irradiation. Interestingly, our results showed that anti-miR-21 increased factors associated with autophagosome formation and autophagy activity, which was measured by acid vesicular organelles, LC3 protein expression, and the percentage of GFP-LC3 positive cells. Furthermore, augmented autophagy by anti-miR-21 resulted in an increase in the apoptotic population after irradiation. Our results show that miR-21 is a pivotal molecule for circumventing radiation-induced cell death in malignant glioma cells through the regulation of autophagy and provide a novel phenomenon for the acquisition of radio-resistance.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Apoptosis / radiation effects
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Autophagy / genetics*
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Brain Neoplasms / genetics*
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Brain Neoplasms / pathology
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Cell Line, Tumor / parasitology
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Cell Survival
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Gamma Rays
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Gene Silencing
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Glioma / genetics*
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Glioma / pathology
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Histones / genetics
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Humans
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MicroRNAs / genetics*
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MicroRNAs / metabolism
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Phosphatidylinositol 3-Kinases / metabolism
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Proto-Oncogene Proteins c-akt / metabolism
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Radiation Tolerance / genetics*
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Signal Transduction / genetics
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Signal Transduction / radiation effects
Substances
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H2AX protein, human
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Histones
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MIRN21 microRNA, human
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MicroRNAs
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Phosphatidylinositol 3-Kinases
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Proto-Oncogene Proteins c-akt
Grants and funding
Jong Bae Park was supported by the National Cancer Center Grant (1010171 and 1010172) of South Korea; Ho-Shin Gwak was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology (2009-0089971); Jinlong Yin was supported by a grant of the Korea Health Technology R&D project, Ministry of Health & Welfare, Republic of Korea (A110878); Jong Heon Kim was supported by the National Cancer Center Grant (1110110) and the National Research Foundation Grant (2012-0008362) of South Korea; Youn-Jae Kim was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (1230920-1); Heon Yoo was supported by the National Cancer Center Grant (1210043-1) of South Korea; Seung Hoon Lee was supported by the National Cancer Center Grant (1210320-1 and 1210042-1) of South Korea. EJB(SEPT23). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. In addition, no additional external funding was received for this study.