YAP基因在卵巢肿瘤发生、恶性转移及卵巢癌干细胞中的作用研究

发布时间：2018-08-17 17:55

【摘要】：近年研究表明,Hippo-YAP信号通路参与哺乳动物器官大小维持、干细胞全能性维持和肿瘤发生。YAP基因作为Hippo信号通路中的核心转录共激活因子,与人类肿瘤的发生关系密切。TEAD家族是YAP基因下游重要的核内转录因子,它的转录活化水平直接影响YAP基因对其下游靶基因的调控及一系列功能行使。目前,YAP作为癌基因的相关研究仅限于体外,在体研究未见报道。在卵巢癌的发生发展过程中,TEAD家族作为YAP基因下游重要的核转录因子,是否参与了YAP诱导卵巢肿瘤发生的过程,TEAD家族中的几个重要亚型是否也都参与其中,以及临床上YAP与TEAD活性与卵巢癌患者预后的关系目前均未见研究报道。另一方面,YAP同样参与了干细胞的干性维持与调控。YAP的高表达能够维持诱导多能干细胞的未分化状态,YAP的表达水平随着干细胞的终末分化而下降。这些研究均提示YAP也可能在癌干细胞的发生、维持与分化中发挥作用。而癌干细胞的存在可能是肿瘤耐药、复发及转移的主要原因。目前,YAP在卵巢癌干细胞中的作用研究也未见报道。因此,进一步深入了解YAP在卵巢癌干细胞中的作用对于揭示YAP在卵巢癌的发生发展及耐药中的作用机制有重要意义。本研究通过体外及体内实验验证了YAP基因促进卵巢癌细胞增殖、肿瘤形成及转移,并且与卵巢癌患者的临床预后密切相关。首先,通过对正常卵巢上皮组织及卵巢肿瘤组织检测证实YAP在卵巢癌中高表达。通过病例随访及生存分析我们证明YAP的高表达与卵巢癌患者临床预后相关。接下来通过一系列体内及体外实验证明YAP促进卵巢癌细胞增殖及肿瘤形成,YAP促进卵巢癌细胞耐药性以及远处转移。TEAD4作为YAP下游转录因子,其活性对于YAP发挥促癌作用非常重要。在本研究中我们首次发现YAP基因的表达水平与TEAD4的表达密切相关,卵巢癌组织中YAP/TEAD的共表达水平能够预测卵巢癌患者预后。已有研究表明YAP信号通路与干细胞全能性关系密切,因此我们推测YAP-TEAD在调节癌干细胞的多能性和自我更新方面可能也起到关键作用。在本研究中我们首次通过体外干细胞分离培养,获得并鉴定了具有干细胞特性的卵巢癌干细胞,首次发现YAP及TEAD家族在卵巢癌干细胞中表达上调,TEAD1、3、4三个亚型参与了YAP对癌干细胞干性维持调控,而TEAD2作用不明显。在干细胞分化方面,我们发现YAP通过结合TEAD活化转录,下调Hippo通路下游靶基因CTGF的表达,上调干细胞干性维持相关基因C-FOS的表达而抑制分化以维持癌干细胞干性。在耐药方面,YAP通过调控GSK3A基因而上调耐药基因ABCB1的表达从而增强卵巢癌干细胞耐药性。在卵巢癌干细胞中,GSK3A参与了YAP对耐药基因的调控而GSK3B并未直接参与,ABCB1确实受到Wnt信号通路中GSK3A的调节。综上所述,本研究主要论证了YAP作为Hippo信号通路中重要的癌基因,通过结合核内转录因子TEAD促进卵巢癌发生及远处转移,与卵巢癌患者预后密切相关。YAP调节卵巢癌干细胞的增殖和分化而增强癌干细胞耐药性。这一机制可能是卵巢癌发生、远处转移及耐药的根本原因。YAP有望作为临床上卵巢癌化疗的一个新的分子药物靶点,为降低卵巢癌复发及远处转移,提高卵巢癌临床治愈率提供新的思路。
[Abstract]:Recent studies have shown that the Hippo-YAP signaling pathway is involved in the maintenance of mammalian organ size, the maintenance of stem cell totipotency and tumorigenesis. As a core transcriptional co-activator in the Hippo signaling pathway, the YAP gene is closely related to the occurrence of human tumors. At present, the study of YAP as an oncogene is confined to in vitro and has not been reported in vivo. During the development of ovarian cancer, TEAD family, as an important downstream nuclear transcription factor of YAP gene, is involved in the development of ovarian cancer induced by YAP. On the other hand, YAP is also involved in the maintenance and regulation of stem cells. The high expression of YAP can maintain the undifferentiated state of induced pluripotent stem cells and the expression of YAP. These studies suggest that YAP may also play a role in the occurrence, maintenance and differentiation of cancer stem cells. The presence of cancer stem cells may be the main cause of tumor resistance, recurrence and metastasis. Understanding the role of YAP in ovarian cancer stem cells is important to reveal the mechanism of YAP in the development and drug resistance of ovarian cancer.
In this study, in vitro and in vivo experiments confirmed that YAP gene promotes ovarian cancer cell proliferation, tumor formation and metastasis, and is closely related to the clinical prognosis of ovarian cancer patients. First, through the detection of normal ovarian epithelial tissues and ovarian tumor tissues confirmed that high expression of YAP in ovarian cancer. It is concluded that the high expression of YAP is associated with the clinical prognosis of ovarian cancer patients. Next, a series of in vivo and in vitro experiments have proved that YAP promotes ovarian cancer cell proliferation and tumor formation, and YAP promotes ovarian cancer cell resistance and distant metastasis. We found for the first time that the expression level of YAP gene was closely related to the expression of TEAD4. The co-expression level of YAP/TEAD in ovarian cancer tissues could predict the prognosis of ovarian cancer patients.
We speculate that YAP-TEAD may also play a key role in regulating the pluripotency and self-renewal of cancer stem cells. Three subtypes of TEAD 1,3,4 are involved in the regulation of YAP on stem cell maintenance, while TEAD 2 is not. In stem cell differentiation, we found that YAP down-regulates the expression of CTGF downstream of the Hippo pathway and up-regulates stem cell maintenance by binding to TEAD activation transcription. In terms of drug resistance, YAP enhances the resistance of ovarian cancer stem cells by regulating the expression of the drug-resistant gene ABCB1 by regulating the GSK3A gene. In ovarian cancer stem cells, GSK3A participates in the regulation of YAP on drug-resistant genes, but GSK3B is not directly involved. ABCB1 is indeed subject to Wnt. Regulation of GSK3A in signaling pathways.
In conclusion, this study demonstrated that YAP, as an important oncogene in the Hippo signaling pathway, promotes the occurrence and distant metastasis of ovarian cancer by binding to the nuclear transcription factor TEAD, which is closely related to the prognosis of ovarian cancer patients. YAP regulates the proliferation and differentiation of ovarian cancer stem cells and enhances cancer stem cell resistance. YAP is expected to be a new molecular drug target for clinical chemotherapy of ovarian cancer, providing new ideas for reducing recurrence and distant metastasis of ovarian cancer and improving the clinical cure rate of ovarian cancer.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R737.31

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