EZH2在直肠癌干细胞中的作用机制及小分子靶向治疗的研究

The biological properties of rectal cancer stem cells, including self-renewal, multi-directional differentiation and high tumorigenicity are considered to be involved in tumor progression, relapse, and therapeutic resistance. Zeste gene enhancer homolog 2 (EZH2) is highly expressed in colorectal cancer stem cells, and leads to the transcriptional silencing of target genes involved in proliferation and differentiation of stem cells. EZH2 may become an effective target to eliminate rectal cancer stem cells. In previous work, we successfully isolated and identified rectal CSCs (RCSCs) for further investigation of the biological properties of CICs in rectal cancer. We also designed, synthesized and identified ZLD10A as a potent inhibitor of methyltransferase EZH2. ZLD10A could significantly inhibit the proliferation and self-renewal of rectal cancer stem cells. The activation of Wnt signaling is essential to maintain the characteristics of CSCs. Previous studies suggests that ZLD10A can affect the expression of E-cadherin, an indirect regulator of Wnt pathway. In this study, ZLD10A is used to further study the effect of EZH2 on rectal cancer stem cells in vivo, and to clarify the key pathways of EZH2 play a role in the treatment of rectal cancer. This study will provide an basis for the treatment of our high incidence rectal cancer.

直肠癌干细胞的自我更新、多向分化及高致瘤性是导致直肠癌复发、多药耐药及转移的根本。Zeste基因增强子同源物2（EZH2）在结直肠癌干细胞中高表达，并且EZH2调控的下游基因多具有抑制肿瘤发生和调控干细胞分化的作用，因此 EZH2可能成为消除直肠癌干细胞的有效靶点。前期我们成功从原代组织中分离、培养并鉴定得到直肠癌干细胞，并通过设计、合成并筛选得到了一个高活性EZH2抑制剂ZLD10A，结果显示ZLD10A能够显著抑制直肠癌干细胞的增殖及自我更新。已知Wnt信号通路的激活对维持肿瘤干细胞的特性至关重要，前期研究发ZLD10A能够影响Wnt通路的间接调节子E-cadherin的表达。本研究拟在前期研究基础上，应用ZLD10A进一步研究EZH2在体内对直肠癌干细胞恶性行为学的作用，特别深入研究ZLD10A激活Wnt通路发挥作用的关键节点分子，为该靶点抑制剂应用于我国高发的直肠癌治疗提供依据。

结直肠癌干细胞的自我更新、多向分化及高致瘤性是导致结直肠癌复发、多药耐药及转移的根本。Zeste基因增强子同源物2（EZH2）在结直肠癌干细胞中高表达,并且EZH2调控的下游基因多具有抑制肿瘤发生和调控干细胞分化的作用，因此EZH2可能成为消除直肠癌干细胞的有效靶点。本项目首先通过设计、合成并筛选得到了一个高活性EZH2抑制ZLD10A。应用ZLD10A研究EZH2在体内外对直肠癌干细胞的自我更新及强致瘤性的作用以及EZH2 在直肠癌干细胞中参与调控的信号通路。结果表明ZLD10A能有效抑制EZH2酶活性，在体外抑制直肠癌干细胞的增殖及自我更新，但是在体内需要在较大剂量下才能一定程度的抑制直肠癌干细胞移植瘤的生长。进一步信号通路研究显示抑制EZH2酶活功能能降低wnt信号通路关键节点蛋白β-catenin的表达，同时对wnt通路中的vimentin及c-myc有明显改变。另外还发现降低EZH2能提高wnt信号抑制基因CXXC4的表达。初步表明EZH2可能通过沉默CXXC4，从而激活wnt信号通路，此结论还需要进一步实验数据验证。另外本团队基于目前EZH2可逆抑制剂出现的耐药，给药剂量大等缺点，研究开发了一类具有高活性的EZH2共价抑制剂。