转移前微环境中Periostin/CCL2/CD36信号轴促肝癌转移起始细胞形成的分子机制研究

Recurrence and metastasis are the main factors influencing the prognosis of liver cancer. Recent studies have shown that metastasis-initiating cells is the key factor to initiate the metastasis process in pre-metastatic niche. Bone marrow-derived endothelial progenitor cells（EPCs）is an important composition in pre-metastatic microenvironment and it act as a switch in this niche. Our previous studies indicated that there have a positive correlation between the Periostin (POSTN) expression level and the colony numbers of EPCs in hepatocellular carcinoma, and high expression of POSTN liver cancer cells with the characteristics of liver cancer stem cells. However, it is not clear whether high expression of POSTN liver cancer cells could transfer to liver metastasis-initiating cells by interacting with EPCs in pre-metastatic niche. In this study, by using a variety of molecular biology experiment and cell co-culture, orthotopic xenograft with co-transplantation into nude mice, POSTN transgenic and knockout mice model with spontaneous hepatocarcinogenesis method, we would test the hypothysis that control the POSTN/CCL2/CD36 axis in pre-metastatic niche could transfer high POSTN expressed liver cancer cells into CD36 positive metastasis-initiating cells. The purpose of this study is to further clarify the role of POSTN played in the metastasis of liver cancer and furthermore, provide a theoretical basis and reliable preclinical data by targeting POSTN/CCL2/CD36 axis as an anti-metastatic therapy strategy of liver cancer.

肝癌转移复发是影响其预后的主要因素，最近研究表明转移前微环境中的转移起始细胞是启动转移的关键因素，骨髓来源的内皮祖细胞是转移前微环境中的重要组分也是启动转移的开关。我们前期研究表明Periostin（POSTN）在肝癌中的表达与内皮祖细胞集落数目呈正相关，且POSTN高表达细胞具有肝癌干细胞的特性，然而在转移前微环境中POSTN高表达肝癌细胞能否通过与内皮祖细胞的相互作用转变为转移起始细胞尚未明确。本研究中我们拟利用分子生物学实验及细胞共培养、裸鼠原位共移植、POSTN转基因及基因敲除小鼠自发性肝癌模型等手段，从分子、细胞及活体水平验证转移前微环境中POSTN/CCL2/CD36轴可促使肝癌细胞转变为CD36阳性的转移起始细胞。通过本研究旨在进一步明确POSTN在肝癌转移过程中的作用，并为以POSTN/CCL2/CD36轴为靶点的肝癌抗转移复发治疗提供可靠的理论依据及详实的临床前期数据。

肝癌是常见的恶性肿瘤之一，肝癌的转移复发是影响肝癌患者远期生存的关键瓶颈，因此，深入探索肝癌转移的分子机制，寻找潜在的治疗靶点是改善肝癌患者预后的关键。Periostin蛋白与肝癌的转移及不良预后相关，肝癌中POSTN及内皮祖细胞是否参与肝癌转移起始细胞形成及其机制未见报导。本研究通过建立POSTN肝脏特异性敲除小鼠DEN诱导的肝癌模型证实POSTN的敲除可有效抑制肝癌转移，同时抑制CD36阳性转移起始细胞形成并抑制EPCs动员。进一步通过肝癌细胞与EPCs的体内外共培养实验确认了POSTN对EPCs迁移、趋化及成管能力的促进作用，同时验证POSTN高表达共培养体系促进了肝癌细胞侵袭、增殖、成球能力的增加及EMT过程并诱导CD36表达增加。本研究还进一步对分析机制进行探究，证实了POSTN通过αvβ3/ILK/NF-κB通路上调了EPCs中CCL2的表达，CCL2通过CCR2/STAT3并结合CD36启动子促进了肝癌细胞中CD36的转录及表达从而促进肝癌转移起始细胞形成。