肝细胞癌中过表达的SULF2通过激活CAF细胞进而抑制肿瘤细胞凋亡的信号通路研究

A great deal of interest has been focused on the role of carcinoma-associated fibroblasts (CAFs) in the progression of cancer. The underlying mechanisms whereby CAFs are induced and promote cancer cell growth in HCC microenvironment remain unclear. In spite that SULF2 overexpression has previously been found in HCC tissues and been associated with worse prognosis after liver resection by our group, the role of SULF2 in HCC progression has not been completely elucidated. Our prelimainary data have validated that SULF2 up-regulates TGFβ1 secretion by HCC cells. Additionally, TGFβ1 has been verified to lead to transformation of mesenchymal cells into CAFs in cancer microenvironment by several groups. Therefore, in the present project, we attempt to validate the novel hypothesis that SULF2 secreted from HCC cells induce transformation of neighbouring hepatic stellate cells into CAFs via accelerating TGFβ1 secretion of HCC cells, and in turn the new born CAFs activate SDF-1/CXCR4/PI3K/AKT signaling cascade of HCC cell by secreting more SDF-1 protein into HCC microenvironment and finally repress HCC cell apoptosis by carrying out the detection of clinical HCC samples, in vitro and in vivo experiements. The aim of this project is to investigate the origin of CAFs in HCC microvironment and the role of CAFs in HCC progression, and in addition elucidate the mechanism that SULF2 promotes HCC progression in order to provide new idea for the research of cancer microenvironment and the scientific basis to exploit novel targeting agents and predictive biomarkers for HCC clinically.

癌相关成纤维细胞（CAFs）相关研究已成为肿瘤研究热点。肝细胞癌（HCC）肿瘤微环境中CAFs从何而来以及活化的CAFs如何影响肿瘤生长的分子机制仍不清楚。我们研究发现硫酸酯酶2（SULF2）蛋白在HCC组织中过表达，且与较差肝癌切除术预后明显相关，但相关机制尚未探明。我们已证实SULF2可以促进HCC细胞分泌TGFβ1，而TGFβ1被证实可将肿瘤微环境间质细胞激活为CAFs。因此，本项目提出科学假说：“HCC中SULF2通过促进肿瘤细胞分泌TGFβ1，将其周围的肝间质细胞转化为CAFs；另一方面，CAFs分泌大量SDF-1蛋白，激活其周围HCC细胞的SDF-1/CXCR4/PI3K/AKT通路进而抑制肿瘤细胞凋亡”，并设计临床标本检测和体内外实验进行验证。通过上述研究，本项目旨在探明HCC肿瘤微环境中CAFs来源和其对肿瘤细胞的影响，并阐明SULF2促癌机制，为肿瘤微环境研究提供新思路。

硫酸硫酸酶2（SULF2）是一种硫酸乙酰肝素6-O-硫酸内酯酶，可从硫酸乙酰肝素蛋白聚糖（HSPG）中除去6-O-硫酸酯基，从而改变各种信号分子的结合位点。我们确定了SULF2在HCC微环境中从肝星状细胞（HSC）到癌相关成纤维细胞的转化中的作用。TCGA数据库中的信息分析表明，SULF2 mRNA表达与包括α-SMA，FAP，波形蛋白和POSTN在内的CAFs标记显着正相关。IHC对102份HCC样品的分析还证实，肿瘤细胞中SULF2表达与HCC组织间充质细胞中α-SMA, FAP，波形蛋白和POSTN的表达之间存在明显的正相关。与表达SULF2的HCC细胞共培养后，发现HSCs可增加CAFs标记物的表达并增强其生长，细胞活力，增殖，迁移和侵袭。在HCC细胞中用siRNA敲低TGFβ1和用特异性抗体中和TGFβ1均阻止了SULF2诱导的HSC和CAF转化。发现CAF通过SDF-1/CXCR4/PI3K/AKT信号传导增强BAD，Caspase 9和FKHRL 1的磷酸化，然后抑制HCC细胞凋亡。 SULF2诱导的CAF增加裸鼠中HCC异种移植的生长并增强HCC的肺转移。总之，在这里发现由HCC细胞分泌的SULF2诱导从邻近HSCs到CAFs的反式分化，从而抑制了HCC细胞凋亡并增强了转移能力。