甲基化修饰的候选抑癌基因DKK2在乳腺癌中调控Wnt和Notch信号通路交叉对话的分子机制研究

Breast cancer is the most common cancer in women. The prognosis of breast cancer is closely related with the invasion and metastasis of cancer cells. The aberrant of Wnt/β-catenin and Notch pathway is involved in EMT, apoptosis resistance and angiogenesis which is essential to invasion and metastasis in breast cancer, and also involved in the maintenance of breast cancer stem cells properties which is the primary cause of metastasis.Our previous study demonstrated that the expression of DKK2, a secreted Wnt antagonist, was frequently silenced in 90.9%(10/11) of breast cancer cell lines by promoter methylation, as compared to human normal mammary epithelial cells and tissues. DKK2 methylation was detected in 72.7% of breast cancer cell lines and 87.6% breast tumor tissue.Furthermore,the expression of DKK2 was negatively related to the grade of breast cancer,and Dkk2 promoter regions contain double Notch-response elements. Consequently, we suppose that the DKK2 which undergoes an epigenetic modification could inhibit the invasion and metastasis through regulating the crosstalk between Wnt and Notch pathway in breast cancer.We plan to focus on the following aspects:1. Analyze methylation of Dkk2 status and the correlation of Dkk2 methylation with clinicopathological features in breast cancer；2. Investigate the effects of Dkk2 on breast cancer growth, invasion, and metastasis；3. Determine the regulation of DKK2 on the cross-talk between Wnt/β-catenin and Notch pathway to unravel the molecular mechanism underlying effects of invasion, and metastasis. In summary, this study can provide a novel insight into understanding the role and the molecular mechanism of DKK2 in breast tumorigenesis and provide a new tumor marker or new drug discovery for breast cancer.

乳腺癌是女性常见的恶性肿瘤,其预后与癌细胞侵袭和转移密切相关。Wnt/β-catenin 和Notch信号通路的异常涉及乳腺癌侵袭转移的三个重要环节（EMT、抵抗凋亡和血管生成）和转移的根源(乳腺癌干细胞干性的维持）。我们前期研究发现Wnt信号通路的负调控因子DKK2在90.9%(10/11)的乳腺癌细胞株中表达沉默, 在72.7%的乳腺癌细胞株及87.6%乳腺癌组织中发生甲基化。DKK2的表达与乳腺癌的分级呈负相关，且DKK2启动子存在Notch的结合位点。因此,我们推测甲基化修饰的DKK2通过调控Wnt和Notch通路的交叉对话而抑制乳腺癌的侵袭转移。本项目拟研究：1.DKK2在乳腺癌中的甲基化状态及临床相关性；2.DKK2对乳腺癌侵袭转移的作用；3.DKK2调控Wnt和Notch 信号通路交叉对话的分子机理。弄清DKK2的作用与调控有关的分子，有望筛选出乳腺癌的诊断标志物或治疗靶点。

乳腺癌是女性常见的恶性肿瘤,其预后与癌细胞侵袭和转移密切相关。Wnt/β -catenin 和 Notch 信号通路的异常涉及乳腺癌侵袭转移的三个重要环节（EMT、抵抗凋亡和 血管生成）和转移的根源(乳腺癌干细胞干性的维持）。我们研究发现 Wnt 信号通路的负调控因子 DKK2 在 100%(8/8)的乳腺癌细胞株中表达沉默, 在 77.8%的乳腺癌细胞株及 86.7%乳腺癌组织中发生甲基化。外源性表达DKK2可改变乳腺癌细胞的形态，抑制细胞增殖和克隆形成，诱导细胞阻止于G0/G1期和细胞凋亡。通过逆转EMT和肿瘤干性标志物而抑制乳腺癌细胞迁移和侵袭，此外，DKK2可抑制肿瘤新生血管形成。体内实验中，DKK2过表达也能抑制裸鼠移植瘤的生长。机理上，DKK2可抑制经典的Wnt/β-catenin 通路和Notch通路，从而抑制乳腺癌的生长及侵袭转移。总的来说，我们首次证实DKK2在乳腺癌中作为Wnt/β-catenin 通路的负调控因子起着抑制基因的作用，其甲基化调控与乳腺癌的临床病理特征相关，可作为乳腺癌的一个早期标志物和治疗靶标。