新型死亡相关基因TIPE1调控小G蛋白信号转导通路阻断肝癌进程的作用研究

Hepatocellular Carcinoma (HCC) is the most common liver malignant tumor, which is the 2nd cause of death among cancer-related disease and very harmful to the human health. To uncover the whole map of mechanism for HCC would benefit the clinical, individual therapy. The abnormal activation of small G protein-mediated signaling pathway is closely related with the development of HCC. A lot of regulatory proteins for this pathway were involved in this process. TIPE1is a newly identified, regulatory gene for cell death. Its biological function and mechanism have not been reported. Our latest study found that TIPE1 is highly expressed in adult liver tissues, but lowly expressed in fetal liver tissue and liver cancer tissues. Moreover, the expression of TIPE1 in HCC tissues was significantly correlated with patient survival, pathological grade and tumor invasion and metastasis. In addition, TIPE1 overexpression induces cell death and inhibits cell proliferation and migration. And, TIPE1 binds with Rac1 and RGL, and downregulates the level of Rac1-GTP and p-Akt. Based on these previous work, we hypothesized that TIPE1 inhibits cells proliferation, migration and disrupts the development of HCC by regulating small G protein-mediated signaling pathway. We will probe into the molecular mechanism of TIPE1 on regulating small G protein pathway and the role in HCC, which would provide useful data for exploring the mechanism of HCC and new target for clinical target therapy.

肝细胞肝癌(HCC)是最常见的肝脏恶性肿瘤，死亡率位居癌症第二位，危害极大。HCC致病机制的全面揭示将为制定完善的个体化治疗方案提供理论依据。小G蛋白信号通路异常激活与肝癌进程密切相关，多种通路调节蛋白参与其中。TIPE1是新型死亡调控基因，其生物学功能和作用机制尚未报道。课题组最新发现，TIPE1在人成年肝组织高表达，而在胚胎肝和HCC组织中显著降低，且在HCC中的表达与生存期、病理分级和浸润转移密切相关；TIPE1可诱导肝癌细胞死亡，抑制增殖和迁移；TIPE1可与Rac1、RGL结合，并下调Rac1-GTP和p-Akt水平。据此提出假说：TIPE1通过调控小G蛋白信号通路抑制细胞增殖和迁移，阻断HCC进程。本课题拟利用体内外模型和临床标本，深入探讨TIPE1调控小G蛋白信号通路的分子机制及其在HCC进程中的关键作用。课题的完成将进一步阐明HCC发病机制，为临床靶向治疗提供新的靶点和思路

肝细胞肝癌(HCC)是最常见的肝脏恶性肿瘤，死亡率位居癌症第二位，危害极大。HCC致病机制的全面揭示将为制定完善的个体化治疗方案提供理论依据。小G蛋白信号通路异常激活与肝癌进程密切相关，多种通路调节蛋白参与其中。TIPE1是新型死亡调控基因，其生物学功能和作用机制尚未报道。本课题研究发现，TIPE1在人成年肝组织高表达，而在胚胎肝和HCC组织中显著降低，且在HCC中的表达与生存期、病理分级和浸润转移密切相关；体内实验和流式细胞术检测结果显示，TIPE1过表达可显著抑制裸鼠移植瘤生长；体外细胞生长曲线、克隆增殖实验结果显示，TIPE1过表达可抑制细胞增殖和克隆形成能力，诱导细胞死亡，反之TIPE1 siRNA可促进细胞增殖；然而，Caspase抑制剂和RIP1抑制剂均不能逆转TIPE1诱导的细胞死亡；免疫共沉淀结果显示，TIPE1可通过与Rac1结合，GST pull-down进一步发现TIPE1可下调Rac1-GTP水平和下游通路分子磷酸化的p65、磷酸化的JNK水平，而Rac1 siRNA和组成活化型Rac1突变体Rac1 Q61L均可逆转TIPE1对细胞增殖和死亡的影响；同时，TIPE1在多种免疫器官和巨噬细胞中具有本底水平的表达，肝癌组织中肿瘤相关巨噬细胞高表达TIPE1，且与患者生存期负相关；肝癌条件性培养基，特别是TGF-β，可剂量依赖性上调巨噬细胞TIPE1表达，并通过调控STAT1/STAT6磷酸化促进巨噬细胞向M2型分化，进而促进肝癌细胞生长和侵袭迁移；进一步研究发现，TGF-β可被TIPE1诱导上调表达，在巨噬细胞表达TIPE1促进肿瘤进程中发挥重要作用。本课题率先研究了肝细胞和巨噬细胞中TIPE1在肿瘤发生中的表达变化，初步研究了TIPE1调控肝细胞死亡、肿瘤相关巨噬细胞极化、细胞因子分泌进而参与肿瘤发生的生物学作用，为揭示TIPE1生物学功能提供新数据，为肿瘤免疫治疗提供潜在的靶点。