METTL3/MYCN cooperation drives neural crest differentiation and provides therapeutic vulnerability in neuroblastoma

Neuroblastoma (NB) is the most common extracranial childhood cancer, caused by the improper differentiation of developing trunk neural crest cells (tNCC) in the sympathetic nervous system. The N6-methyladenosine (m6A) modification controls post-transcriptional gene expression but the mechanism by which the m6A methyltransferase complex METTL3/METTL14/WTAP is recruited to specific loci remains to be fully characterized. We explored whether the m6A epitranscriptome could fine-tune gene regulation in migrating/differentiating tNCCs. We demonstrate that the m6A modification regulates the expression of HOX genes in tNCCs, thereby contributing to their timely differentiation into sympathetic neurons. Furthermore, we show that posterior HOX genes are m6A-modified in MYCN-amplified neuroblastoma with reduced expression. In addition, we provide evidence that sustained overexpression of the MYCN oncogene in tNCC drives METTL3 recruitment to a specific subset of genes including posterior HOX genes, creating an undifferentiated state. Moreover, METTL3 depletion or inhibition induces DNA damage and differentiation of MYCN-overexpressing cells and increases vulnerability to chemotherapeutic drugs in MYCN-amplified patient-derived xenografts in vivo, suggesting METTL3 inhibition as a potential therapeutic approach for NB.

神经母细胞瘤（Neuroblastoma, NB）是最常见的颅外儿童恶性肿瘤，其发病机制为交感神经系统内发育中的躯干神经嵴细胞（trunk neural crest cells, tNCC）分化异常。N6-甲基腺嘌呤（N6-methyladenosine, m6A）修饰可调控转录后基因表达，但m6A甲基转移酶复合物METTL3/METTL14/WTAP被招募至特定基因组位点的具体分子机制仍有待全面阐明。本研究探讨了m6A表观转录组是否能够对迁移/分化中的躯干神经嵴细胞的基因调控进行精准微调。研究证实，m6A修饰可调控躯干神经嵴细胞内同源盒基因（HOX genes）的表达，进而推动其按时序分化为交感神经元。此外，本研究发现，在MYCN扩增型神经母细胞瘤中，后部同源盒基因（posterior HOX genes）存在m6A修饰且表达水平下调。同时，本研究提供实验证据表明，在躯干神经嵴细胞中持续过表达MYCN癌基因，可促使METTL3被招募至包括后部同源盒基因在内的特定基因子集，进而维持细胞的未分化状态。进一步实验显示，在体内环境中，对MYCN过表达细胞敲除或抑制METTL3，可诱导DNA损伤并促进细胞分化，同时可提升MYCN扩增型患者来源异种移植瘤（patient-derived xenografts）对化疗药物的敏感性，这提示METTL3抑制有望成为神经母细胞瘤的潜在治疗策略。