Pleiotropic functions of FOXC2 in EMT, stem cells and breast cancer progression

描述（由申请人提供）：癌症干细胞（CSC）在乳腺癌进展和化疗耐药性中起关键作用。 最近，我们发现乳腺癌细胞中上皮-间充质转化（EMT）的诱导赋予干细胞属性。 我们还鉴定了叉头转录因子FOXC 2作为EMT基础间充质程序的协调者和转移能力的关键调节因子。 我们的初步研究表明，FOXC 2的抑制导致EMT的逆转和功能性干细胞特性的丧失。 此外，从正常乳腺组织或乳腺上皮细胞系分离的干细胞中FOXC 2表达更高。 FOXC 2在EMT和乳腺癌干细胞的十字路口的这种明显定位表明，它或其效应物对于具有间充质和干细胞特性的乳腺癌细胞的维持和/或功能至关重要。 在这个提议中，我们将采用双系统方法-体外细胞培养模型和Foxc 2条件性敲除小鼠-来描述Foxc 2在正常乳腺稳态和癌症进展中的多效性功能。 我们将交叉Foxc 2条件敲除转移倾向的转基因，以确定Foxc 2消融肿瘤的发生和转移的后果，并测试Foxc 2是干细胞样属性和耐药性的关键调节因子的假设体内化疗。 此外，我们已经确定PDGFR-B是FOXC 2下游的一个假定的可药物靶点，我们将评估PDGFR靶向药物在根除FOXC 2表达的EMT衍生CSC中的疗效。 因此，该项目将提高我们对CSC和EMT在乳腺癌进展中的作用的理解，并将提出推定的FOXC 2分子效应物，其可用于靶向具有EMT/CSC属性的转移能力细胞。

DESCRIPTION (provided by applicant): Cancer stem cells (CSCs) play a critical role in breast cancer progression and chemoresistance. Recently, we found that induction of an epithelial-mesenchymal transition (EMT) in breast cancer cells confers stem cell attributes. We also identified the Forkhead transcription factor FOXC2 as an orchestrator of the mesenchymal program underlying EMT and a key regulator of metastatic competence. Our preliminary studies show that suppression of FOXC2 leads to reversion of EMT and loss of functional stem cell properties. Moreover, FOXC2 expression is higher in stem cells isolated from normal mammary tissues or mammary epithelial cell lines. This apparent positioning of FOXC2 at the crossroads of EMT and breast cancer stem cells suggests that it or its effectors are essential for the sustainment and/or functioning of breast cancer cells with mesenchymal and stem cell properties. In this proposal, we will employ a dual systems approach - an in vitro cell culture model and a Foxc2 conditional knockout mouse - to delineate the pleiotropic functions of Foxc2 in normal breast homeostasis and cancer progression. We will cross Foxc2 conditional knockouts to metastasis-prone transgenics to determine the consequences of Foxc2 ablation on tumor initiation and metastasis and test the hypothesis that Foxc2 is a critical regulator of stem-like attributes and resistance to chemotherapy in vivo. In addition, we have identified PDGFR-B as a putative druggable target downstream to FOXC2 and we will evaluate the efficacy of PDGFR-targeted agents in eradicating FOXC2-expressing EMT-derived CSCs. Thus this project will improve our understanding of the role of CSCs and EMT in breast cancer progression and will suggest putative FOXC2 molecular effectors that may be exploited to target metastatically-competent cells with EMT/CSC attributes.