肝癌细胞外泌体传递VASH2蛋白通过激活内皮细胞促进肝癌转移的机制研究

The early metastasis of hepatocellular carcinoma(HCC) accounted for the poor prognosis of HCC. It was reported that exosomes, as the communication mediator between tumor and matrix cells, took part in the formation of the pre-metastatic niche, thus promoted tumor metastasis, but the underlying mechanisms were unclear.Our team found that Vasohibin-2(VASH2) gene was transcriptionally activated and could promote epithelial-mesenchymal transition in HCC for the first time.Continuous research showed that VASH2 protein could be secreted in the form of exosomes. The content of VASH2 in the serum of HCC patients was higher than in healthy control. In vitro studies displayed that exosomes-derived VASH2 activated endothelial cells. In vivo studies confirmed that VASH2-rich exosomes induced angiogenesis and further metastasis in the lung of experimental mice. Therefore,we proposed that the exosomal VASH2 protein derived from hepatocarcinoma cells could activate the endothelial cells(ECs), form the pre-metastatic niche and promote metastasis. To confirm our hypothesis, exosomes from HCC were isolated by ultracentrifugation and identified by membrane markers. ELISA was used to measure the content of exosomal VASH2 in the serum of clinical patients. Further experiment was taken to reveal the function and mechanism of exosomal VASH2 on tumor angiogenesis and formation of metastasis. Our project around the exosomal VASH2 and pre-metastatic niche will provide new thought and target for treatment of progressive HCC.

肝细胞癌预后差的根源是其早期发生转移，研究表明，外泌体作为肿瘤细胞与基质细胞间的通讯介质参与转移前微环境的形成，从而促进肿瘤转移，但具体机制尚未明确。申请者团队前期报道了VASH2基因在肝癌中转录激活，诱导肝癌细胞发生EMT；持续研究发现VASH2蛋白以外泌体形式分泌至细胞外，在肝癌患者血清中VASH2的含量明显高于健康对照；体外实验发现外泌体传递VASH2激活内皮细胞；体内实验证实富含VASH2的外泌体诱导小鼠肺内血管新生并促进肺转移。据此提出假说：肝癌细胞来源的外泌体传递VASH2蛋白激活内皮细胞，诱导转移前微环境形成，并促进转移。为此本项目首先分离肝癌外泌体并鉴定，进而检测患者血清VASH2的含量；从分子、细胞及动物水平明确外泌体传递的VASH2对血管生成及肿瘤转移的作用；在此基础上探讨下游分子通路。围绕外泌体VASH2蛋白这一核心为揭示肝癌转移的机制奠定基础，并提供潜在的治疗靶点。

肝细胞癌（HCC）是全球最常见的癌症类型之一。每年有超过750，000人被诊断出患有这种疾病1.尽管在诊断和治疗方面取得了进展，包括手术技术和肝移植，但HCC患者的长期生存率仍然很低。因此，需要新的生物标志物和治疗靶点来改善肝细胞癌患者的预后。血管抑制素2（VASH2）以前被确定为血管生成因子，但其在肿瘤发生中的作用尚不清楚。前期有研究发现VASH2可激活内皮细胞，体内实验证实富含VASH2的外泌体诱导小鼠肺内血管新生并促进肺转移。我们认为：肝癌细胞来源的外泌体传递VASH2蛋白激活内皮细胞，诱导转移前微环境形成，并促进转移。