抑癌基因Nkx2.8抑制膀胱癌细胞上皮-间叶转变（EMT）的分子机制

Human Nkx2.8 (Nk2 homeobox 8), a novel member of the NK2 gene family, was found in a study of human neoplastic gene regulation. We have previously found that the expression level of Nkx2.8 protein was significantly associated with the prognosis of bladder cancer. Up-regulation of Nkx2.8 resulted in deactivation of MEK/ERK pathway and inhibition of proliferation in bladder cancer cells (Carcinogenesis,2012). Further studies have demonstrated that up-regulation of Nkx2.8 inhibited epithelial-mesenchymal transition (EMT), an early key event in cancer metastasis, in bladder cancer cells. However, the molecular mechanisms are still not clear. In the present study, we will use ChIP assay, IP and test of promotor activity in up-regulating and down-regulating of Nkx2.8 models, aimed to demonstrate the mechanisms of how Nkx2.8 regulating E-cadherin gene expression. We will also aimed to explore that whether and how Nkx2.8 regulate Twist related pathways. In vivo animal model will also be used to validate the role of Nkx2.8 in regulating bladder cancer cell invasion and metastasis. In conclusion, our study will reveal the mechanisms of bladder cancer metastasis and find a new therapy target for this disease.

Nkx2.8是NK2家族中可能影响肿瘤发生的一个新成员。我们的前期研究发现Nkx2.8表达水平与膀胱癌预后密切相关，上调Nkx2.8能够通过抑制MEK/ERK/FOXO3a信号通路使膀胱癌细胞增殖受抑制（Carcinogenesis,2012）。预实验发现上调Nkx2.8能够抑制肿瘤转移的早期关键事件-上皮间叶转变（EMT），上调E-cadherin的表达并减弱肿瘤细胞的侵润能力，但其分子机制仍有待阐明。本研究拟以Nkx2.8高表达和RNAi下调Nkx2.8表达的膀胱癌细胞为模型，通过染色体免疫共沉淀、蛋白免疫共沉淀及启动子活性测定等方法，阐明Nkx2.8对E-cadherin基因的表达调控机制；探讨Nkx2.8调控Twist转录因子的相关信号通路；并通过活体动物模型确定Nkx2.8调节EMT和膀胱癌细胞侵润转移的功能，为阐明膀胱癌转移机制和确定新的治疗靶点提供科学依据。

Nkx2.8是NK2家族中可能影响肿瘤发生的一个新成员。我们的前期研究发现Nkx2.8表达水平与膀胱癌预后密切相关，上调Nkx2.8能够通过抑制MEK/ERK/FOXO3a信号通路使膀胱癌细胞增殖受抑制（Carcinogenesis,2012）。预实验发现上调Nkx2.8能够抑制肿瘤转移的早期关键事件—上皮间叶转变（EMT），上调E-cadherin的表达并减弱肿瘤细胞的侵润能力，但其分子机制仍有待阐明。本研究中我们以Nkx2.8高表达和RNAi下调Nkx2.8表达的膀胱癌细胞为模型，通过染色体免疫共沉淀及启动子活性测定等方法，阐明了Nkx2.8通过直接结合TWIST1的启动子抑制TWIST1基因转录，从而抑制膀胱癌细胞的EMT及体内转移能力；进一步研究发现Nkx2.8对Twist1的抑制作用与膀胱癌患者的预后相关，Nkx2.8阳性且Twist1低表达的患者预后明显比其他组好。因此，我们的研究为阐明膀胱癌转移机制和确定新的治疗靶点提供了科学依据。