LncRNA MAL介导的多蛋白泛素化在细胞恶性转化和乳腺癌发生中的作用及机制研究

解析恶性转化的动因是理解癌症发生与演进的重要基础，是否存在除基因突变外的表观遗传机制诱发细胞转化有待深入研究。MDM2作为重要癌蛋白，调控多种抑癌蛋白降解。我们通过筛选与MDM2结合并对其有调控作用的功能性lncRNA，寻找新型癌基因。前期发现lncRNA MAL在不典型增生及乳腺癌组织中表达明显高于正常乳腺组织，且与患者的不良预后相关。同时，MAL促进乳腺上皮细胞成瘤并增强多种乳腺癌细胞恶性表型。基于以上结果提出科学假设：MAL通过与MDM2的直接相互作用增强其活性，使得下游多种抑癌蛋白泛素化降解增加，发挥促癌功能。本项目拟进一步通过类器官培养，转化相关及体内成瘤实验，明确MAL在肿瘤发生中的作用，并阐明MAL对MDM2发挥调控作用的具体机制。该研究的顺利进行有助于深入认识肿瘤起始的原动力同时发掘lncRNA调控MDM2功能的新机制，为靶向干预特定肿瘤信号通路提供理论依。

Clarifying the core steps in tumorigenesis and malignant transformation are important for understanding the initiation, progression and chemotherapy resistance of cancer, and helpful to investigate the novel synergistic strategy for cancer treatment. Whether epigenetic mechanisms besides genetic mutations could induce cell transformation needs further study. The oncoprotein MDM2 is an important member of the E3 ubiquitin ligase family and regulates the degradation of various tumor suppressors including p53. We performed RNA immunoprecipitation and sequencing (RIP-seq) to screen for functional MDM2-binding lncRNAs and lncRNA MAL was one of them. Our preliminary data showed that the expression of MAL gradually increased in benign, atypical hyperplasia, ductal carcinoma in situ(DCIS), and invasive ductal carcinoma(IDC) specimens, and it was negatively correlated with the clinical prognosis of breast cancer patients. At the same time, MAL promotes tumorigenesis of primary human mammary epithelial cells (HMECs) and enhances the malignant phenotype of multiple breast cancer cells. Herein we proposed that MAL directly binds to MDM2 and promotes tumorigenesis through enhancing MDM2 ubiquitin ligase activity to increase the degradation of multiple tumor suppressor proteins. This project intends to further explore the specific molecular mechanism of MAL. Through organoids culture, transformation experiments in vivo and tumor formation experiments in vitro, the contribution of MAL in tumorigenesis and development of breast cancer will be clarified. The results may not only provide further understanding of novel driver genes in tumorigenesis and regulatory mechanisms of lncRNA on MDM2 activity, but insights and targets to develop therapeutic strategies.