CNSC-28. The Importance of M5c Rna Modifications in Epitranscriptomics for Glioblastoma

Glioblastoma is the most aggressive brain tumor in adults. Despite surgical resection, chemo- and radiotherapies, patients have a median overall survival of less than 2 years. Recently DNA analysis has been developed and defined the characteristics of glioma. Accordingly, the m5C modification on DNA are well reported. Though it is also known as an RNA modification, the role of the m5C RNA modification in GBM is not well understood. The m5C modification is a methylation of the fifth carbon of cytosine to 5-methylcytosine. Here, we report the importance of m5C modifications on RNA in GBM. We extracted total RNA from tumor and non-tumor portions of our GBM patient samples and investigated the ratio of each modification (tumor/non-tumor) using RNA modification analysis which is a highly sensitive and comprehensive detection of various RNA-modified nucleosides by mass spectrometry. We found that several RNA modifications were decreased in GBM. Next, we compared the amount of each RNA modification that showed changes. The m5C, m1G, and m2G had higher ratios than the other modifications. The expression and prognosis of modification enzymes (Writer), de-modification enzymes (Eraser), and proteins that recognize and act on each modification (Reader) were examined, and significant differences were found in the expression levels and prognosis of several proteins that act in the regulatory mechanism of the m5C modification. We analyzed the data of TCGA and CCGA and found that the expression of NSUN5 and NSUN7 in Writer and YBX1 in Reader were upregulated in GBM, and the higher the expression, the worse the prognosis. In addition, when we focused on the analysis to recurrent or malignant transformation cases, higher expression of several other m5C-related proteins (NOP2, NSUN2, NSUN6, TRDMT1, and TET2) were also tended to be associated with worse prognosis. These results indicate that not only the previously known m5C modifications in epigenetics, but also m5C modifications in epitranscriptomics are important for GBM.