外泌体与肿瘤转移——【国自然标书写作】

外泌体与肿瘤转移

外泌体（exosome）是由细胞内多囊泡体与细胞膜融合后，释放到胞外基质中的一类直径约为30-100nm的膜性囊泡，其分布和来源广泛，可由多种细胞所分泌1, 2。且其内容物丰富，携带有蛋白、脂质和核酸等，参与了如免疫应答、抗原提呈、胞间通讯、蛋白质和RNA 转运等多种生理过程，是一种重要的胞间物质和信息交流的工具3, 4。

尽管外泌体可由多种细胞类型分泌，但其数量和内容物的种类与母细胞的生理状况息息相关。研究表明，病理条件下的细胞（如肿瘤细胞）释放外泌体的水平显著增加，且外泌体的内容物组分较正常生理条件下的有所不同，这不仅强调了母细胞对外泌体内容物的靶向精密调节，也暗示了其在肿瘤形成和发展过程中的重要作用5, 6。例如，暴露于低氧环境中的乳腺癌细胞通过低氧诱导因子HIF-1α一定程度地上调了外泌体的分泌量；而低氧条件下的鳞状细胞癌细胞所分泌的外泌体中含有更高水平的与血管生成相关的蛋白7, 8。

越来越多的基础和临床研究表明，肿瘤细胞的外泌体与肿瘤的发生和恶化有关，其能够调控免疫功能，促进肿瘤血管新生和侵袭转移，甚至直接作用于其他肿瘤或非肿瘤细胞，从而影响细胞或组织的命运5。如当肿瘤外泌体与初始活化的T细胞共培养时，发现其能下调CD3ξ、JAK3的表达并介导Fas/FasL驱使的CD8+T细胞凋亡，反映出肿瘤外泌体的免疫抑制特性9。而且，肿瘤细胞外泌体介导了VEGF和CXCR4信号通路的调控，从而增强血管生成和肿瘤生长10。研究发现，外泌体通过其特定内容物能够介导肿瘤细胞迁移，如所包含的MMP-2具有降解胞外基质胶原纤维的作用11；黑色素瘤细胞的外泌体载有MET受体酪氨酸激酶，当其转移至骨髓细胞中可促进肿瘤的转移12；而体外实验发现，外泌体影响了肿瘤细胞的定向迁移13；其所包含的异常高水平microRNAs能够促进肿瘤细胞的侵袭和转移14-16。另一方面，由

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于外泌体含有microRNAs，且肿瘤在形成和发展过程中伴随着外泌体向胞外基质的释放，因此通过对体液中外泌体及外泌体RNA（eRNA）的检测将为肿瘤的临床诊断和预后评估提供新的视野17, 18。

总之，外泌体作为肿瘤微环境中的一个重要组分，参与了胞间信号转导以及肿瘤形成和恶化过程。对肿瘤外泌体研究的深入将有助于揭示肿瘤形成和转移过程背后的分子机制，为肿瘤的临床诊治提供全新的思路。

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