CK2α在维持肝癌干细胞特性中的作用及机制研究

The presence and stemness of liver cancer stem cell is one of the main reasons for treatment difficulty and recurrence of hepatocellular carcinoma(HCC). Epithelial Mesenchymal Transition (EMT) can enhance liver cancer stem cell phenotype, and the Hedgehog(Hh) signal pathway can promote tumor EMT process. Project Leader preliminary study demonstrated that CK2α could promote hepatocellular carcinoma cell EMT and up-regulate Hh Signaling. Meanwhile, it have been reported that CK2α played a role in the regulation of tumor stem cells. However, it have not been reported whether CK2α regulate hepatocellular carcinoma EMT by Hh Signaling, and the relationship of CK2α with liver cancer and liver cancer stem cells. Therefore we proposed the hypothesis of this project that CK2α could control liver cancer stem cell properties and mediate insensitivity to chemotherapy via regulating hepatocellular carcinoma cells EMT by Hh signaling. In order to prove this hypothesis, firstly, the significance of CK2α and Hh-EMT signaling expression in hepatocellular carcinoma would been analyzed. Secondly, it would been demonstrated that CK2α could promote liver cancer stem cell phenotypic characteristics and mediate cell insensitivity to chemotherapy through activating the Hh-EMT signal pathway. Finally, the effects of CK2α expression on CD133(+)liver cancer stem cell characteristics would been detected. The successful implementation of this project will illuminate the new mechanism of chemotherapy insensitivity and recurrence of HCC, and there will be huge clinical values for improving the survival rate of HCC patients.

肝癌易复发难治，原因之一是肝癌干细胞的存在及其特性的维持。上皮间质转化(EMT)能促进肝癌干细胞表型，刺猬(Hedgehog, Hh)信号能促进EMT进程；项目负责人前期研究发现CK2α能促进肝癌细胞的EMT，并上调Hh信号。同时有报道指出CK2α对肿瘤干细胞具有调控作用；而CK2α是否通过Hh信号调控肝癌EMT进而维持肝癌干细胞特性、CK2α与肝癌、肝癌干细胞的关系未见报道。因此提出假说“CK2α在维持肝癌干细胞特性中发挥重要作用，其主要机制是通过Hh信号调控肝癌细胞EMT，维持肝癌干细胞特性”。为了证实该假说本项目首先分析CK2α、Hh-EMT在肝癌组织中表达的意义；其次论证CK2α表达对CD133(+)肝癌干细胞特性的影响；最后论证CK2α通过活化Hh-EMT维持干细胞特性。本项目将阐明CK2α调控肝癌干细胞特性的作用及分子机制，为干预肝癌侵袭、逆转化疗不敏感等治疗难题提供理论依据。

肝癌是全球最常见的恶性肿瘤之一，其临床特点是进展快、预后差，发现晚，肝切除及介入治疗后肿瘤易复发、且对化疗药物不敏感，化疗效果不显著，严重影响肝癌患者生存。CD133(+)肝癌干细胞的存在与肝癌发生、发展及不良预后密切相关。研究调控CD133(+)肝癌干细胞特性机制及信号传导通路在肝癌复发转移及化疗药物不敏感的机制对肝癌的治疗、延长肝癌患者生存期具有极其重大的意义。.上皮间质转化(epithelial-mesenchymal transition，EMT)在胚胎发育、组织重建、癌症转移等疾病中发挥了重要作用。肿瘤细胞发生EMT对肿瘤干细胞特征的形成非常重要，肿瘤细胞经历EMT能获得干细胞样表型，在肿瘤转移、化疗药物耐受和再生复发中发挥了重要作用。有研究表明EMT能有效促进肝癌干细胞表现干细胞特性。刺猬信号通路(Hedgehog, Hh)是在胚胎发育，调控祖细胞生长分化及组织形成中发挥了重要作用，主要由配体Hedgehog(Hh)、跨膜蛋白受体Patched(Ptch)和Smoothened(Smo)以及下游转录因子Gli)级联构成。当Hh缺失时，该信号通路处于抑制状态；反之则激活Hh通路。我们前期研究提示Hedgehog信号可能在肝癌干细胞干性维持中发挥重要作用，但有待进一步深入研究。.蛋白激酶CK2是一种普遍存在的多功能信使非依赖性丝/苏氨酸蛋白激酶，由两个催化亚基(α或α’)和两个调节亚基(β)构成的不均一四聚体。前期研究证实蛋白激酶CK2α在肝癌细胞系中高表达，并可能通过Hedgehog信号通路促进肝癌细胞发生EMT 。.本项目验证了CK2α在肝癌组织中高表达，结合GEO数据库发现CK2α表达水平与肝癌的恶性程度、组织分化、淋巴结转移等不良预后正相关，通过体内外实验研究结果发现沉默或过表达CK2α后Hedgehog-EMT相关蛋白分子也随之下降或升高，并且伴随CD133+肝癌干细胞侵袭转移耐药能力降低或上升，即沉默CK2α，Hedgehog-EMT正相关分子指标下降，CD133+肝癌干细胞标志分子表达降低，干细胞体外迁移侵袭能力下降，异种移植瘤模型中肿瘤细胞生长减慢，肿瘤体积缩小，化疗药物敏感性升高，所以我们推测CK2α通过Hedgehog信号调控EMT来维持肝癌干细胞特性，介导肝癌耐药、复发与转移，这为成为肝癌治疗靶点选择提供了理论依据。