METTL3介导RNA m6A修饰在膀胱癌发生发展过程中作用和机制的系统研究

Bladder cancer is the world's most common type of urogenital cancer, with a high recurrence rate and poor prognosis. The epigenetic regulation of bladder cancer is still elusive and need further investigation. Recent advances in mRNA epitranscriptomics revealed that mRNA modifications such as N6-Methyladenosine (m6A) play important roles in post transcriptional regulation of a variety of genes, which then involved in many physiological or pathological processes. Latest studies suggest the mis-regulated m6A modification participate in carcinogenesis and tumor progression. However, the role and mechanism of m6A mediated by METTL3 is still not known in bladder cancer. Our preliminary study revealed that the expression of m6A RNA methyltransferase METTL3 is significantly up-regulated in bladder cancer tissues from both human and mouse, and knockdown of METTL3 reduced the proliferation and invasion but raised apoptosis in bladder cancer cells. In this study, we will systematically investigate the role and mechanism of METTL3 mediated m6A in bladder cancer progression by using in vitro cell assay, conditional knockout transgenic mice and human samples, and explore the key downstream target genes and signaling pathways involved. This project will help to identify novel RNA epigenetic regulation mechanisms in bladder cancer and provide new insights for clinical diagnostics and treatment of bladder cancer.

膀胱癌具有较高的复发率，预后不佳，其发生发展的表观遗传学机制研究尚不清楚。近年来的研究发现发生在mRNA上的m6A修饰对基因表达具有重要调控作用。m6A修饰广泛参与多种重要生理进程及疾病的发生，目前已有研究表明m6A修饰异常参与调控了恶性肿瘤生成及进展。然而，膀胱癌中METLL3介导的m6A修饰发挥的作用仍无研究。我们前期研究发现METTL3在人和鼠的膀胱癌样品中的表达均高于正常组织，且敲降METTL3可以明显抑制膀胱癌细胞的增殖，迁移和干细胞成球，并导致细胞凋亡。本研究项目将在细胞水平，条件性转基因敲除小鼠水平和临床样本水平研究METTL3和m6A修饰在膀胱癌发生发展过程中的作用，鉴定受METTL3介导的m6A修饰直接调控的下游关键癌基因及相关信号转导途径，明确m6A调控膀胱癌进展的机制。本课题研究结果将揭示膀胱癌发展的新的RNA表观遗传机制，对膀胱癌的诊断和治疗具有重要意义。

膀胱癌极易复发且预后较差。免疫检查点抑制剂为主的肿瘤免疫治疗仅在一小部分患者中取得疗效，为此仍需要进一步探索免疫检查点调控机制，为肿瘤免疫治疗提供新的思路。有证据表明JNK信号通路在肿瘤发生发展中的功能具有双面性，一方面JNK促进自噬以对抗细胞凋亡，另一方面可通过免疫逃逸调控肿瘤的生长。本研究通过化学诱导膀胱癌小鼠模型和皮下成瘤小鼠模型，联合体外细胞实验研究确认JNK信号通路异常激活导致膀胱癌肿瘤组织/细胞中的METTL3表达上调，并引起多个基因的异常m6A甲基化修饰增高，包括NFkB，AFF4，Myc和PD-L1等，从而介导肿瘤组织的干性、增殖和免疫逃逸。本研究首次在体内及体外发现m6A甲基化修饰的上游调控信号及JNK抑制剂在治疗膀胱癌的作用，证实JNK信号的下调可以抑制膀胱癌中的免疫逃逸能力，为膀胱癌的临床治疗提供了全新的思路。