Detection and quantification of extracellular microRNAs in medulloblastoma

Abstract

Aim: Medulloblastoma (MB) is the most common malignant brain tumor in children. The crucial role of extracellular-microRNAs (ex-miRNAs) in cancer has been widely recognized; however, their role in MB remains unknown. This study aimed to investigate MB-driven ex-miRNAs. Methods: Microarray analysis was used to disclose the identity and quantity of key miRNAs excreted in culture-medium (CM) of 3 human MB cell lines and cerebrospinal fluid (CSF) of brain tumors (including MB) and leukemia patients. MiRNA expression was validated by quantitative reverse transcription polymerase chain reaction. Results: We have demonstrated that the 3 MB cell lines tested commonly expressed 1,083 miRNAs in their spent CM. Among them, 57 miRNAs were specific to the CM of metastasis-related cell lines which represents the aggressive group 3 and group 4 MB subtypes. A significant number (1,254) of ex-miRNAs were identified in the CSF of a MB patient. Eighty-six of these miRNAs were found to be differentially expressed in this patient's CSF compared with controls. Interestingly, 3 metastasis-associated miRNAs over-represented in CM of metastasis-related MB cell lines were found to be significantly enriched in the CSF of the MB patient. Conclusion: Although more samples are required to fully verify these results, our work provides the first evidence for the presence of a significant amount of miRNAs excreted extracellularly by MB cells and raises the possibility that, in the near future, miRNAs could be probed in CSF of MB patients and serve as novel biological markers.