神经母细胞瘤NB是儿童最常见颅外恶性实体肿瘤，分化程度与生存率密切相关。维甲酸RA诱导NB分化，作用机制仍有待深入研究。前期RA处理NB细胞转录组测序示YTHDF2和DLK1表达显著降低、miR-675-3p表达显著升高。过表达YTHDF2阻断RA引起的细胞分化和增殖抑制，DLK1 mRNA稳定性增加；沉默YTHDF2细胞形态出现分化、增殖抑制。数据库分析示YTHDF2或DLK1低表达肿瘤分化好；miR-675-3p与YTHDF2有结合位点；DLK1有m6A修饰的motif，且与NB分化相关。综上，提出假说“RA通过miR-675-3p调控YTHDF2表达，降低DLK1 mRNA的稳定性引起NB细胞分化”。本项目拟在细胞和动物水平改变miR-675-3p、YTHDF2或DLK1表达，明确三者间的调节机制，探讨调控RA诱导NB细胞分化的分子机制。为临床诱导NB分化转归及精准治疗提供新靶点。

Neuroblastoma (NB) is the most common malignant solid tumor of children, the degree of differentiation is closely related to the overall survival ratio of patients. Retinoic acid (RA) was used to induce NB differentiation in clinical, but the mechanisms still need to be deeply studied. We performed RNA-Seq to explore the mechanisms of RA-induced NB cell differentiation, and the results show that the expressions of YTHDF2 and DLK1 were significantly decreased, and the expression of miR-675-3p was significantly increased. Overexpress YTHDF2 could block RA-induced cell differentiation and inhibition of cell proliferation, and increase the stability of DLK1 mRNA; knockdown the expression of YTHDF2 could induce cell differentiation and inhibit cell proliferation. Using database analysis, we found that the tumor has a better differentiation with low expression of YTHDF2 or DLK1; and between miR-675-3p and YTHDF2 exist binding sites; and DLK1 exists a motif that can be modified by m6A, and DLK1 has been reported to involve in NB cell differentiation. Based on the above, we hypothesis "RA regulates the expression of YTHDF2 via miR-675-3p, which decreases the stability of DLK1 mRNA and induces NB cell differentiation." This program will study the regulating mechanism between miR-675-3p, YTHDF2, and DLK1, and the mechanisms of RA-induced NB cell differentiation by changing the expressions of them at cellular level and animal level. The aim of this study is to provide a new target for inducing NB differentiation and precise treatment in clinical.