| Summary: | 碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 103 === Neuroblastoma (NBL) is a pediatric cancer derived from the sympathetic lineage of the neural crest with improper differentiation during development. The amplification of V-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) is a clinical feature associated with the poor prognosis of NBL while the underlying mechanism still remains elusive. In this study, we first integrated several expression datasets from Gene Expression Omnibus (GEO) and performed significance analysis of microarrays (SAM) in high-risk NBL of patients with or without MYCN amplification. We found that MTHFD2 (methylenetetrahydrofolate dehydrogenase (NADP+ dependent) 2, methenyltetrahydrofolate cyclohydrolase), a mitochondrial enzyme required for one-carbon metabolism and purine synthesis, was differentially up-regulated in NBL with MYCN amplification (P < 0.001). Additionally, in our chromatin immunoprecipitation (ChIP) - sequencing assay, we observed that MYCN strongly bound to promoter region nearing by MTHFD2 transcriptional start site (P = 3.7e-18). MTHFD2 is essential to embryonic development and has been shown to relate to the poor survival in breast cancer. It was also found that high MYCN and MTHFD2 expression correlated with poor survival (P < 2.4e-13) from our survival analysis in NBL patients. Based on data analyses above, we speculated that MYCN and MTHFD2 may play related role in NBL. To confirm this, we reduced and overexpressed MYCN expression, respectively, and observed MTHFD2 expression levels concomitantly changing in NBL cell lines. Moreover, promoter assay revealed that MTHFD2 is a direct transcriptional target of MYCN. To this end, we also conducted shRNA-mediated knockdown experiments in SK-N-DZ cells and overexpressed MTHFD2 in SK-N-AS cells. Interestingly, MTHFD2 promotes cell proliferation and colony formation of NBL cell lines. Together, our results suggest that MTHFD2 may play an important role in tumor aggressiveness as a potential therapeutic target for NBL.
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