可移动miRNA诱导肿瘤和转移灶周围细胞“同化共生”的表观遗传学基础研究

Tumor metastasis to distant organ sites usually leads to the failure of cancer treatment. Interaction between metastasized tumor cells and cells co-localized with tumor colony could establish the tumor-favoring microenvironment, which is believed to be one of the most important steps during tumor metastasis. Highly-expressed-miRNAs in some tumor account for tumor growth and metastasis. The "moving'' and stability make miRNA as an excellent genetic or epigenetic messenge transmitter among different cells. Gap junctions and microvesicle are important cellular communication pathways, by which miRNA can move from cell to cell. We hypothesized "assimilation" may occur among metastatic cells and others around. In this model, the tumor cells can actively secret or release miRNA to "assimilate" cells co-localized with tumor colony in order to help themselves to thrive. By checking the biological changes and cellular morphology of tumor cells in co-culture system, we want to verify that miRNA could move between cells working as a messenge transmitter, which is very important during the process of tumor metastasis. Blocking the miRNA moving may be an efficient strategy to inhibit tumor cells metastasis. Supporting this project will help us to re-think the mechanisms underlying metastasis, and provide new strategy for early diagnosis and treatment of tumor.

肿瘤细胞向远端器官转移最终导致肿瘤治疗失败。肿瘤细胞与转移灶周围细胞相互作用形成有利于肿瘤细胞生长的微环境是肿瘤转移的重要一步。肿瘤组织特征性的miRNA表达与肿瘤细胞生长和转移密切相关。miRNA的可移动性及稳定性使其能够成为细胞间信息传递的重要载体，细胞间的连接体以及microvesicle是细胞间物质交换的重要途径，miRNA可能通过以上途径进行传递。本项目提出肿瘤转移异位生长的"同化共生"假说，认为肿瘤细胞释放或分泌可移动性的miRNA，"同化"周围细胞使肿瘤细胞与周围细胞"互利共生"。本研究通过肿瘤细胞在共培养体系中生物学行为研究，证实miRNA在肿瘤细胞及共培养细胞间的"移动"，确定肿瘤细胞间可移动的miRNA具有"信使"功能，验证移动性miRNA在肿瘤转移中的作用，确认阻断miRNA移动可抑制肿瘤转移的有效性。本研究有助于阐明肿瘤转移新机制，为肿瘤转移诊断与治疗提供新思路。

肿瘤转移是肿瘤治疗的最大障碍之一。目前研究认为肿瘤细胞与转移灶周围细胞的信息交流是肿瘤转移微环境的重要因素，肿瘤特征性miRNAs表达与转移密切相关。为探究肿瘤细胞分泌的可移动miRNAs是否能参与肿瘤细胞对转移灶周围细胞的基因表达调控及生物学行为控制，本项目以相同遗传背景但转移潜能显著差异的两种骨肉瘤细胞为研究模型，确定了肿瘤细胞通过胞外囊泡miRNAs介导的基因表达调控对细胞生理活动的影响，首次发现1）高转移性骨肉瘤细胞系143B可分泌丰富的胞外囊泡，同时这些胞外囊泡能够被受体细胞摄取至细胞内，并诱导增强低转移性骨肉瘤细胞系MNNG的转移能力；2）143B细胞中显著高表达的肿瘤相关miRNAs在其分泌的胞外囊泡中富集；3）MiR-1246是143B细胞分泌的胞外囊泡中促肿瘤转移的关键miRNA, 可通过经典的3’UTR靶向结合机制下调一系列的肿瘤抑制基因的表达；同时可通过靶向增强子区域调控组蛋白修饰激活肿瘤相关基因的表达，以双重表观遗传调控机制诱导肿瘤转移能力的增加。本项目的研究结论进一步巩固了肿瘤细胞可通过胞外囊泡miRNA进行转移灶微环境改造的概念；另外，我们的研究凸显了胞外囊泡中兼备有肿瘤癌基因激活的一类miRNAs的重要性，并阐明了其对肿瘤细胞基因表达和细胞生理活动的表观遗传调控机制，对全面理解肿瘤转移的分子机制和肿瘤治疗具有重要意义。