核转录因子OCT4上调VEGF-C表达促进食管鳞状细胞癌上皮-间质转化及转移的机制研究

Nuclear transcription factor OCT4 plays an important role in maintaining cancer cell proliferation,preventing cancer cells from differentiation, and especially promoting cancer stem cells to renew themselves. In our previous study, we found that there was a little OCT4 positive cells in esophageal cancer, which can cause cancer cells to present the process of Epitheilal-mesenchymal transition (EMT), and prevent cancer cells from anoikis. Cytology experiments have showed that OCT4 could increase vascular endothelial growth factor C (VEGF-C) expression and promote esophageal squamous cell carcinoma (ESCC) EMT. Moreover, over-expression of VEGF - C could induce EMT in ESCC cells.Therefore, we hypothesized that OCT4 might promote ESCC EMT and metastasis via OCT4 mediated up-regulation of VEGF-C expression.In this project, we will evaluate the role of OCT4/ VEGF-C in the EMT of ESCC by multiple approaches including clinical investigation ,luciferase reporter assay, ChIP, adenovirus mediated gene delivery, and metastasis assay in NOD/SCID mice. It will help us to establish effective gene treatment strategies targeting to esophageal carcinoma. The study can provides theoretical basis and efficiency target genes for esophageal carcinoma biological therapy.

核转录因子OCT4在维持癌细胞增殖和肿瘤干细胞自我更新、阻止癌细胞分化等过程中起重要作用。我们在前期研究中发现，食管癌中有很少部分的癌细胞OCT4呈阳性表达，可引起癌细胞上皮间质转化（EMT），阻止癌细胞发生失巢凋亡，与癌细胞高增殖转移活性密切相关；同时细胞学实验显示，高表达OCT4能够上调血管内皮生长因子C (VEGF-C)表达并促进肿瘤发生EMT；此外，高表达VEGF-C同样可以诱导食管癌细胞发生EMT，但相关分子机制不明。据此，我们推测OCT4可能通过在转录水平对VEGF-C表达进行调控，促进食管肿瘤细胞发生EMT。本项目拟在前期研究的基础上通过ChIP、荧光素酶报告基因、转基因或基因沉默、动物成瘤转移并结合临床统计分析进一步明确其信号通路，从而加深对OCT4调控癌细胞增殖分子机制的了解。本项研究具有较强的创新性，如获成功，将为食管癌生物靶向治疗提供新的有效靶标。

OCT4对促进癌细胞增殖转移和肿瘤干细胞自我更新起重要作用。食管癌（ECC）细胞系及组织中存在多少不一的OCT4阳性、具有肿瘤干细胞特征的癌细胞，这些OCT4阳性的细胞恶性度高，易发生淋巴结转移，但相关机制尚不清楚。本文通过对ECC细胞系的研究发现，OCT4通过激活VEGF-C启动子的活性而促进VEGF-C表达，激活VEGFR-3的磷酸激酶活性，继而诱导癌细胞发生EMT。ECC裸鼠移植瘤实验证实，OCT4能够促进移植瘤的生长速度和肺转移发生，而下调OCT4的表达则能达到控制癌细胞转移的作用。通过对临床标本的检测分析，发现OCT4和VEGF-C阳性表达的ECC具有更恶性的生物学行为，患者预后不良。研究证实，ECC的发生发展过程中存在一条OCT4/VEGF-C/VEGFR-3/EMT的信号调控通路。OCT4通过激活VEGF-C/VEGFR-3信号传导，诱导癌细胞发生EMT，从而提高癌细胞侵袭转移能力，促进肿瘤发展。对OCT4调控ECC细胞EMT及转移发生机制的阐释，为开展ECC转移机制和生物治疗的研究提供了有用的靶点。我们在顺利完成本课题原计划的同时，本课题组积极探索食管癌增殖转移的分子机制，我们发现OCT4可以通过上调CCND1促进食管鳞癌细胞增殖、miR214可以通过下调GALNT7抑制食管鳞癌细胞增殖等。