SNAIL-Dependent Regulation of EMT in Cancer

描述（由申请人提供）：E-钙粘蛋白表达下调是称为上皮-间充质转化（EMT）的关键发育程序的标志，这是一个经常被显示侵袭性表型的癌细胞利用的过程。锌指转录因子Snail是E-钙粘蛋白基因表达的强大阻遏物，其可以单独或与Wnt信号级联一起发挥作用以在正常以及肿瘤细胞中诱导EMT。在最近的研究中，我们证明了蜗牛蛋白嵌入有β-连环蛋白样基序，支持其通过GSK 3 β磷酸化及其随后的β-TrCP指导的泛素化和蛋白酶体降解。此外，已经建立了一种操作模型，其中经典Wnt信号传导以合作方式稳定Snail和β-连环蛋白的细胞内水平，以参与控制EMT程序的转录机制。基于一系列新的初步数据，我们现在确定了一种新的调节级联，其中经典Wnt信号传导和β-连环蛋白/TCF转录级联通过诱导GSK 3 β核质运输的Axin 2依赖性调节来启动EMT。通过触发核GSK 3 β输出，核Snail蛋白半衰期稳定，并通过与膜锚定金属蛋白酶基因家族成员表达相关的过程参与经典EMT程序-包括癌细胞侵袭和内渗。因此，我们现在提出i）通过Snail/β-连环蛋白/TCF轴表征Wnt启动的癌细胞EMT的调节，ii）通过Axin 2定义β-连环蛋白/TCF诱导的EMT的Snail依赖性调节，iii）定义Axin 2核质运输和Snail依赖性EMT的结构-功能关系，以及iv）表征GSK 3 β核质运输的Axin 2依赖性控制。细胞质运输及其对蜗牛依赖性EMT的影响。这些研究不仅应该确定Wnt，β-catenin/TCF和Snail在调节癌症EMT中的联锁作用，而且还应该确定治疗干预的新靶点。

DESCRIPTION (provided by applicant): Down-regulation of E-cadherin expression is a hallmark of a key developmental program termed the epithelial-mesenchymal transition (EMT), a process often exploited by cancer cells that display an invasive phenotype. The zinc finger transcription factor, Snail, is a powerful represser of E-cadherin gene expression that can function alone or together with the Wnt signaling cascade to induce EMT in normal as well neoplastic cells. In recent studies, we demonstrated that the Snail protein is embedded with beta-catenin-like motifs supporting its phosphorylation by GSK3beta and its subsequent beta-TrCP-directed ubiquitination and proteasomal degradation. Further, an operational model has been established wherein canonical Wnt signaling stabilizes intracellular levels of Snail and beta-catenin in cooperative fashion to engage transcriptional mechanisms that control the EMT program. Based on a body of new preliminary data, we now identify a novel regulatory cascade wherein canonical Wnt signaling and the beta- catenin/TCF transcriptional cascade initiate EMT by inducing the Axin2-dependent regulation of GSK3beta nucleo-cytoplasmic trafficking. By triggering nuclear GSK3beta export, nuclear Snail protein half-life is stabilized and a classic EMT program engaged - including cancer cell invasion and intravasation - via a process linked to the expression of membrane-anchored metalloproteinase gene family members. As such, we now propose to i) characterize the Wnt-initiated regulation of carcinoma cell EMT by the Snail/beta-catenin/TCF axis, ii) define the Snail-dependent regulation of beta-catenin/TCF-induced EMT by Axin2, iii) define the structure-function relationships underlying Axin2 nucleo-cytoplasmic trafficking and Snail-dependent EMT and iv) characterize the Axin2-dependent control of GSK3beta nucleo-cytoplasmic trafficking and its impact on Snail-dependent EMT. These studies should not only define the interlocking role of Wnt, beta-catenin/TCF and Snail in regulating EMT in cancer, but also identify new targets for therapeutic intervention.