Pygo2是新近发现的β-catenin下游结合蛋白，在果蝇和部分哺乳动物组织的Wnt信号转导中不可缺少。我们先前的研究证明Pygo2在扩增乳腺癌干细胞中发挥重要作用，然而Pygo2是否调节乳腺癌侵袭、转移仍然不清楚。本项目前期实验发现， Pygo2表达与肿瘤进展正相关，TGF-β信号可以通过PI3K-Akt磷酸化增强Pygo2的蛋白表达以及与甲基转移酶MLL2-HMT、乙酰基转移酶GCN5-HAT的结合能力。在乳腺癌细胞中knockdown Pygo2的表达，能明显削弱TGF-β信号刺激引起的细胞形态、侵袭迁移能力以及EMT标志物的变化，表明Pygo2参与了TGF-β信号介导的EMT过程。本课题将首先在分子和细胞水平证明Pygo2调节乳腺癌 EMT的作用，然后应用转基因/基因敲除小鼠体内研究Pygo2调节乳腺癌 EMT的作用，最后分析临床标本建立Pygo2与肿瘤进展的相关性。

Pygo2 is a newly found β-catenin associated protein, which is essential for Wnt signaling transduction in both drosophila and some of mammalian tissues. Our published study demonstrated that Pygo2 plays a pivotal role in expansion of breast cancer stem cells; however, weather Pygo2 regulates the invasion and metastasis of breast cancer is still obscure. Our previous study of this proposal showed that Pygo2 expression is positively correlated with the cancer progression. Moreover, the cancer/pericancerous tissue ratio for Pygo2 protein expression is much higher than that of mRNA. Pygo2 protein but not mRNA level presented time and dose dependent increase upon TGF-β stimulation. Further studies indicated that LY294002, the PI3K-Akt specific inhibitor could effectively inhibit the TGF-β function in Pygo2 expression improvement and phosphorylation, and impair the association between Pygo2 and MLL2-HMT or GCN5-HAT. These results suggest that TGF-β signaling may improve the Pygo2 expression as well as the binding ability between Pygo2 and the downstream proteins via the PI3K-Akt phosphorylation. Knockdown of Pygo2 expression in breast cancer cells resulted in impaired the changes in cell morphology, migration, invasion and EMT markers stimulated by TGF-β, which suggests that Pygo2 is involved in TGF-β signaling mediated EMT process. In this proposal, we will at first demonstrate the upstream and downstream mechanisms for Pygo2 in regulating EMT of breast cancer cells in both molecular and cellular levels. Then, we will perform the in vivo study of Pygo2 in regulating EMT process by virtue of transgenic /knockout mouse models. Finally, we will analyze the clinical samples to establish the correlation between Pygo2 and cancer progression.