SYK(L)通过肝星状细胞介导的微环境抑制肝癌侵袭转移

Hepatic stellate cell (HSC) is the major subtype of stromal cells in the liver tumor microenvironment, which plays an important part in promoting the invasion and metastasis of hepatocellular carcinoma (HCC). Our previous studies demonstrated that SYK two isoforms SYK(L) and SYK(S) exert opposing functions in HCC. SYK(S) promotes HCC invasion and metastasis through activation of ERK/EMT signaling pathway. SYK(L) plays a role of a tumor-suppressor in HCC, but the underlying mechanism is unknown. Preliminary study indicated that that SYK(L) decreased the level of TGF-β1 in HCC cells, and further affected the MMP-9 level secreted by HSCs. Therefore, we hypothesized that SYK(L) may inhibit HCC invasion and metastasis through the tumor microenvironment mediated by HSCs. To investigate the impact of SYK(L) on HCC invasion among the interaction between HCC and HSC, we will first use HCC/HSC co-culture system and co-transplanted tumor models in nude mice after intervention SYK(L) expression in HCC cells or HSCs, respectively. Furthmore, chromatin immunoprecipitation (ChIP), co-immunoprecipitation and other exprements will be applied to explore the molecular mechanism of SYK(L) on regulating TGF-β1 expression. In addition, with the detection of the expression of key proteins of SYK(L)/TGF-β1 signaling pathway in HCC samples, we will explore whether this pathway could predict the recurrence and metastasis among patients with HCC. This study would help to elucidate the mechanism of invasion and metastasis in HCC, and offer new evidences of potential targeted therapies for HCC.

肿瘤微环境在肝癌侵袭转移中作用重要，肝星状细胞(HSC)是其主要的间质细胞。前期研究发现肝癌SYK基因两种异构体功能迥异：SYK(S)经ERK/EMT通路促进肝癌侵袭转移，而SYK(L)发挥抑癌基因功能，但机制不明。预实验示SYK(L)抑制肝癌细胞(HCC)中分泌型蛋白TGF-β1的表达，进而影响HSC的MMP-9分泌；因此，推测SYK(L)可能通过HSC介导的微环境抑制肝癌侵袭转移。本研究拟分别干预HCC/HSC中SYK(L)表达，运用细胞共培养、裸鼠共移植瘤等模型，研究HCC-HSC相互作用中SYK(L)对肝癌细胞侵袭能力的影响；采用ChIP、免疫共沉淀等技术探索SYK(L)调控TGF-β1表达的分子机制；通过检测肝癌组织SYK(L)/TGF-β1通路关键分子的表达，明确其在肝癌复发转移中的预测价值。本课题旨在阐明SYK(L)抑制肝癌侵袭转移的分子机制，为寻找潜在治疗靶点提供新的依据。

微环境在肝癌侵袭转移中发挥重要作用，肝星状细胞(HSC)是肝脏微环境中的主要间质细胞。前期研究发现肝癌SYK基因两种异构体功能迥异：SYK(S)经ERK/EMT通路促进肝癌侵袭转移，而SYK(L)发挥抑癌基因功能。本研究拟探讨SYK基因在肝脏微环境主要间质细胞HSC中的功能，以及对肝纤维化/肝癌的影响。. . 在CCl4诱导的小鼠肝纤维化模型、DEN诱导的大鼠肝纤维化/肝癌模型、以及大鼠胆管结扎肝纤维化模型中，伴随着纤维化程度加重，SYK表达呈升高趋势；进一步分析发现SYK(L)和SYK(S)两种异构体在肝纤维进程中，两者上升趋势一致，以全长型SYK(L)表达为主。肝星状细胞LX-2和TWNT-4中分别过表达SYK(L)和SYK(S)，发现SYK两种异构体均促进肝星状细胞的激活。这些结果提示：肝星状细胞中SYK两种异构体SYK(L)和SYK(S)功能基本一致，均促进HSC激活，影响肝纤维化与肝癌进展。. . 在HBV、HCV或酒精等慢性肝损伤的影响下，诱导肝细胞中SYK表达升高，进而通过TGF-β1等细胞因子发挥细胞间的交互作用，促进肝星状细胞激活与增殖，最终加速肝纤维化进程和肝癌发生发展。选用三种不同致病机理的鼠肝纤维化/肝癌模型【CCl4诱导的小鼠肝纤维化模型、DEN诱导的大鼠肝纤维化/肝癌模型、以及大鼠胆管结扎肝纤维化模型】，采用SYK抑制剂小分子化合物GS-9973进行治疗，结果提示GS-9973可有效缓解肝纤维进程，以及肝癌的发生。此外，GS-9973可抑制肝纤维化基础上的肝癌生长与转移，并延长小鼠生存期，而对正常肝脏基础上的肝癌移植瘤没有显著影响，表明GS-9973可通过肝纤维化相关的肝脏微环境发挥抗肿瘤作用。. . 因此，肝癌细胞中SYK(L)发挥抑癌功能；但肝星状细胞中SYK(L)与SYK(S)均促进HSC的激活与增殖。SYK有望成为肝纤维治疗的有效靶点，并可防治肝纤维化基础上的肝癌发生发展。