Fli-1靶向上调VEGF-C促进鼻咽癌转移的分子机制和临床意义研究

Fli-1 is associated with the growth of various types of cancers, but the role of Fli-1 and its mechanism in nasopharyngeal carcinoma (NPC) are unclear. In our previous study, overexpression of Fli-1 in tumor tissues was significantly correlated with advanced N stage, high risk of metastasis and poor survival of patients with NPC. We also found that Fli-1 was a VEGF-C promoter binding protein using the Biotin-Streptavidin pulldown technique. Knockdown of Fli-1 by siRNA markedly inhibited VEGF-C expression and cell viability in NPC cells. Thus, we hypothesize that Fli-1 could upregulate VEGF-C expression and promote the growth and metastasis of NPC, and may be a potential therapeutic target. In this study, we will (1) demonstrate the binding site(s) in the VEGF-C promoter using report gene assay, ChIP and EMSA, (2) find the regulation pathway and the effect on tumor growth and migration by knockdown and overexpression of Fli-1, as well as the Fli-1 inhibitor in NPC cells and animal models, and (3) detect the prognostic significance of Fli-1 and VEGF-C by analyzing the expression in tumor tissues and sera. Our study will provide evidence for establishing Fli-1 as a pivotal prognostic marker and therapeutic target in NPC.

Fli-1与多种肿瘤生长密切相关,但在鼻咽癌的作用和机制未知。前期我们发现高表达Fli-1的鼻咽癌N分期晚、转移率高、生存率低;通过生物素-亲和素垂钓系统证明Fli-1是VEGF-C启动子结合蛋白;敲低Fli-1下调VEGF-C,抑制鼻咽癌细胞增殖、侵袭和迁移。据此,我们推测Fli-1靶向上调VEGF-C,进而促进鼻咽癌生长和转移,该通路为潜在的鼻咽癌治疗靶点。本项目拟用报告基因、ChIP和EMSA等方法,明确Fli-1靶向调控VEGF-C以及它在后者启动子上的核心结合位点;在鼻咽癌细胞及动物模型中,敲低或过表达Fli-1或使用Fli-1抑制剂,研究Fli-1靶向调控VEGF-C和它们对肿瘤生长和转移的影响及其分子机制;并分析患者肿瘤组织和血清中Fli-1和VEGF-C的表达,评估其在鼻咽癌诊断和预后判断中的意义。本项目旨在证明Fli-1/VEGF-C通路可用于筛选和治疗高转移风险鼻咽癌。

FLI1作为一个转录因子在肿瘤发生和发展中发挥着双向作用，它既可以促进肿瘤的进展，又有文献报道它也可以抑制一些肿瘤的发展。但是FLI1在鼻咽癌中的表达和临床意义，以及FLI1生物学功能和作用机制，目前均无文献报道。我们研究发现FLI1在鼻咽癌组织中高水平表达，与淋巴转移和T分期密切关联。高表达FLI1的患者具有较差的预后。进一步的功能研究发现，FLI1低表达可以抑制细胞增殖和肿瘤生长，并能抑制细胞的迁移侵袭，反之，过表达FLI1，则可以促进鼻咽癌细胞增殖和迁移。在机制研究中我们发现FLI1可以激活VEGFC的启动子活性，并能促进VEGFC的基因表达，进而促进细胞增殖、肿瘤生长和转移。此外我们还发现，FLI1促进细胞生长和转移可能通过活化WNT信号通路和与EMT通路有关。并且，进一步的机制研究，我们发现FLI1可以与SUMO1存在直接的相互作用，后者通过泛素化修饰，保持FLI1的稳定性，促进FLI1的转录激活功能。进而影响FLI1的促进鼻咽癌生长和转移的功能。我们的研究揭示了FLI1在鼻咽癌进展中的癌基因样功能，明确了其发挥功能的分子机制主要是通过影响EMT通路，WNT信号通路和VEGFC通路。我们的研究为揭示鼻咽癌发生发展的分子机制以及FLI-1本身的表达调控提供重要信息，为预防和治疗恶性鼻咽癌提供重要的理论依据。通过靶向这些新的分子靶点，为探索治疗鼻咽癌的新方法提供很好的实验和理论依据。