干细胞转录因子Oct4/Nanog激活Stat3信号促进肝癌侵袭转移的分子机制

Oct4 and Nanog,expressed in both embryonic and adult stem cells,are master transcription factors essential for maintaining stem cells self-renewal and pluripotency.Recently, increasing evidence showed Oct4 and Nanog were also expressed in cancer stem cells and associated with aggressive tumor behaviors and poor prognosis.In previous study,we found both Oct4 and Nanog were linked to metastatic potential in HCC cell lines,and proved coexpression of Oct4 and Nanog can predict recurrence/metastasis and poor clinical outcomes for patients with HCC after curative liver resection.Moreover,results from preliminary experiment suggested Oct4/Nanog may promote invasion and metastasis of HCC through the activation of Stat3 signaling pathway.This study is a further investigation of the possible underlying molecular mechanism of stemness factors Oct4 and Nanog in promoting recurrence/metastasis of HCC. To this end,we will forcibly overexpress Oct4 and Nanog into MHCC97L cell by using plasmid transfection.The role of Oct4 and Nanog in malignant biological behaviors of HCC will be obversed. Phosphorylation of Stat3 and the activation of downstream genes such as MMPs,VEGF,bFGF,Snail,Slug, Twist will also be detected, by a series of in vitro and vivo assays.This is a piloted study involved in stemness factors Oct4 and Nanog driven invasion and metastasis of HCC, which may contribute novel prognostic markers and potential therapeutic targets to the treatment of recurrence and metastasis for HCC．

Oct4及Nanog是在胚胎干细胞及成体干细胞中表达并维持干细胞自我更新及多能性的关键转录因子。近来研究表明，Oct4及Nanog在多种实体瘤的肿瘤干细胞中阳性表达，并与肿瘤的恶性生物学行为及不良预后相关。申请人前期研究发现：Oct4及Nanog基因在高转移潜能肝癌细胞株上调表达，其阳性表达与肝癌患者根治性切除术后肿瘤复发，转移及不良预后相关。进一步研究提示,Oct4和Nanog可能通过介导Stat3信号活化促进肝癌的侵袭转移，然而其涉及的分子机制及信号通路并不明确。本研究拟通过慢病毒转染技术，建立过表达Oct4及Nanog肝癌细胞株，在体内及体外观察Oct4及Nanog过表达对肝癌恶性生物学行为的影响及其对Stat3及相关下游基因MMPs,VEGF,bFGF,Snail,Slug,Twist等调控作用，明确其促进肝癌侵袭转移的分子机制，为肝癌复发转移的预测及靶向治疗提供新的分子标记物。

Oct4及Nanog是维持胚胎干细胞及成体干细胞自我更新及多能性的关键转录因子,与肿瘤的恶性生物学行为及不良预后相关。申请人前期研究发现：Oct4及Nanog基因在高转移潜能肝癌细胞株中上调表达，并与肝癌患者根治性切除术后肿瘤复发，转移及预后不佳相关。为明确OCT4/Nanog促进肝癌复发转移的分子生物学机制，在本课题中，我们建立了过表达Oct4 及Nanog的97L-ON肝癌细胞株，通过体外及体内实验研究其分子生物学特征。一方面，过表达Oct4及Nanog97L-ON细胞形态发生了上皮间质化改变，侵袭转移能力明显升高，EMT相关标志物E-Cadherin下调,而N-Cadherin、Vimemtin、Snail发生上调；另一方面，Oct4及Nanog过表达诱导肝癌细胞发生干性转化。97L-ON细胞的干细胞标志物表达升高，自我更新能力及化疗耐药能力明显强于对照细胞株。将97L-ON细胞株及其对照组细胞进行皮下种瘤，发现97L-ON细胞成瘤能力升高，肝内播散及肺转移明显较对照组增多。信号通路机制研究发现，共表达Oct4及Nanog通过Stat3/Snail信号调控肝癌侵袭转移。综上，本课题明确了过表达干细胞转录因子Oct4/Nanog能促进肝癌细胞干性转化，并通过上调Stat3/Snail信号通诱导肝癌细胞发生上皮间质转换，导致肿瘤侵袭转移。本研究为肝癌复发转移的预测及靶向治疗提供了新的分子标记物及治疗靶点。