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上皮-间质转化（EMT）这一关键发育过程的标志，这一过程经常被癌细胞利用，表现出侵袭性表型。锌指转录因子Snail是一种强大的E-cadherin基因表达抑制因子，可以单独或与Wnt信号级联一起在正常细胞和肿瘤细胞中诱导EMT。在最近的研究中，我们证明了蜗牛蛋白嵌入了β -连环蛋白样基序，支持gsk3 β磷酸化及其随后的β - trcp定向泛素化和蛋白酶体降解。此外，已经建立了一个操作模型，其中典型的Wnt信号以合作的方式稳定了Snail和β -连环蛋白的细胞内水平，从而参与控制EMT程序的转录机制。基于一系列新的初步数据，我们现在确定了一个新的调控级联，其中典型的Wnt信号和β - catenin/TCF转录级联通过诱导依赖于axin2的gsk3 β核-胞质运输调节来启动EMT。通过触发核gsk3 β的输出，核蜗牛蛋白的半衰期稳定，并通过一个与膜锚定金属蛋白酶基因家族成员表达相关的过程参与了一个经典的EMT程序，包括癌细胞的侵袭和体内浸润。因此，我们现在提出i)表征wnt通过Snail/ β -catenin/TCF轴对癌细胞EMT的调控，ii)定义Axin2对β -catenin/TCF诱导的EMT的蜗牛依赖性调控，iii)定义Axin2核-胞质转运和蜗牛依赖性EMT的结构-功能关系，iv)表征Axin2依赖性gsk3 β核-胞质转运的控制及其对蜗牛依赖性EMT的影响。这些研究不仅应该明确Wnt、β -catenin/TCF和Snail在癌症中调控EMT的联锁作用，还应该确定新的治疗干预靶点。

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.