脂多糖通过TLR4-Nanog信号通路促进肝前体细胞成瘤性的机制研究

Accumulating evidence has shown that the activation of hepatic progenitor cells (HPCs) was involved in the occurrence and development of liver cancer. The fate of HPCs is dependent on the microenvironment of liver. Our previous study found that, as an important inflammatory factor of various liver diseases, lipopolysaccharide (LPS) promotes the self-renewal of HPCs. It induces maturation arrest of HPCs and blocks their differentiation into mature hepatocytes and formation of a bile duct-liked structure. More importantly, long-term treatment with LPS promotes tumorigenesis of HPCs in nud mice. However, detailed mechanisms of LPS on tumorigenesis of HPCs remains unknown. TLR4 is the bridge between chronic inflammation and tumorigenesis. Nanog is a key transcription factor. It is highly expressed in cancer stem cells and is thought as an oncogene to promote carcinogenesis. It was proved that Nanog was activated by TLR4. Our preliminarily data demonstrated that intervening the expression of TLR4 and Nanog by shRNA could inhibit tumorigenesis of HPCs after LPS treatment. And the expression of Nanog was increased in HPCs with LPS treatment iva TLR4. The result of bioinformatics analysis implied that TLR4-mediated activation of Nanog might require Jak-Stat signaling pathway.Our further research is to investigate the role of TLR4-Nanog signaling pathway in inducing tumorigenesis of HPCs by LPS. And take a further step to explore the molecular regulatory mechanism of LPS on TLR4-Nanog pathway in HPCs. The results of this study provide us a deeper understanding of the origin of liver cancer and the inflammatory microenvironment, but also provide a new theoretical underpinning for HPCs transplantation.

肝前体细胞（HPCs）的癌化被认为是肝脏肿瘤的起源，同时HPCs也是修复肝损的重要来源。在肝脏病理微环境中，平衡HPCs成瘤性及再生性的具体因素和机制尚不明确。我们前期研究发现：脂多糖（LPS）的长期作用促使HPCs发生成熟抑制，导致其成瘤，但其机制未明。Nanog高表达于肿瘤干细胞，被认为是致癌基因。我们前期预实验发现：在LPS的作用下HPCs中Nanog的表达水平上调，其表达受到TLR4的调控；此外初步证实LPS促进HPCs的成瘤依赖于TLR4及Nanog；同时通过生物信息学分析发现，Jak-Stat通路很有可能参与了HPCs中TLR4对Nanog表达的调控。本项目拟在此基础上，深入研究TLR4及Nanog在LPS促进HPCs成熟抑制及成瘤中的作用；明确HPCs中TLR4调节Nanog表达的具体机制。为肝脏肿瘤形成的起源以及未来HPCs的细胞移植治疗的可行性提供理论基础。

肝前体细胞（Hepatic Progenitor Cells，HPCs）及脂多糖（lipoplysaccharide，LPS）是肝脏肿瘤微环境中的不可忽视的重要成分。但对于LPS、HPCs以及肝癌三者之间的具体作用关系仍不明确。我们通过生信分析发现：LPS的作用靶点TLR4及HPCs的biomarkers（CD133、NCAM1、KRT7、KRT19、EPCAM）均高表达于癌旁。并且TLR4与HPCs的biomarkers的表达存在显著的正相关关系。此外癌旁HPCs的biomarkers的高表达以及toll样受体信号通路的高活化提示肝癌患者的不良预后。在大鼠的原发肿瘤模型中我们发现：LPS及HPCs共同作用促进了肝脏肿瘤的进展。而在体外实验中，我们观察到：经 LPS处理后的HPCs培养上清能够促进肝癌细胞的增殖、迁移、侵袭。于此同时，进一步通过液相芯片及ELISA检测，我们明确LPS能够促进HPCs分泌更多的CXCL5。而在CXCL5的作用下，肝癌细胞具有更高的恶性程度。我们的研究揭示了HPCs不仅仅是肝脏肿瘤微环境中的组成部分，同时HPCs也参与了肝脏肿瘤微环境的重塑。我们的研究结果有助于从肿瘤微环境的角度重新认识肝前体细胞，为临床诊疗提供了新思路和理论依据。