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

描述(申请人提供)：癌症干细胞(CSCs)在乳腺癌进展和化疗耐药中起关键作用。最近，我们发现，在乳腺癌细胞中诱导上皮-间充质转化(EMT)可以赋予干细胞属性。我们还确定了Forkhead转录因子FOXC2是EMT背后的间充质程序的协调者，也是转移能力的关键调节因子。我们的初步研究表明，抑制FOXC2会导致EMT逆转和功能干细胞特性的丧失。此外，FOXC2在从正常乳腺组织或乳腺上皮细胞系分离的干细胞中的表达更高。FOXC2明显处于EMT和乳腺癌干细胞的十字路口，这表明它或其效应器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。在这项提案中，我们将使用双系统方法--体外细胞培养模型和FOXC2条件基因敲除小鼠--来描述FOXC2在正常乳腺动态平衡和癌症进展中的多效性功能。我们将通过FOXC2条件敲除和易于转移的转基因来确定FOXC2消融对肿瘤启动和转移的影响，并测试FOXC2是体内干细胞样属性和化疗耐药性的关键调节因子的假设。此外，我们已经确定PDGFR-B是FOXC2下游的一个可能的药物靶点，我们将评估PDGFR靶向药物在根除表达FOXC2的EMT来源的CSCs方面的效果。因此，这个项目将提高我们对CSCs和EMT在乳腺癌进展中的作用的理解，并将提出可能的FOXC2分子效应因子，可能被利用来靶向具有EMT/CSC属性的具有转移能力的细胞。

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.