Function of Focal Adhesion Kinase Scaffolding to Mediate Endophilin A2 Phosphorylation Promotes Epithelial-Mesenchymal Transition and Mammary Cancer Stem Cell Activities in Vivo
Function of Focal Adhesion Kinase Scaffolding to Mediate Endophilin A2 Phosphorylation Promotes Epithelial-Mesenchymal Transition and Mammary Cancer Stem Cell Activities in Vivo
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DOI：
10.1074/jbc.m112.420497
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发表时间：
2013-02-01
影响因子：
4.8
通讯作者：
Guan, Jun-Lin
中科院分区：
文献类型：
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作者：
Fan, Huaping;Zhao, Xiaofeng;Guan, Jun-Lin
酪氨酸激酶已被证明在癌症的发展和进展中起关键作用，其抑制剂具有作为乳腺癌和其他癌症的有效靶向治疗的潜力。然而，这些激酶中的一些如粘着斑激酶（FAK）也在细胞内信号传导中具有支架功能，但FAK或其他激酶的这种激酶非依赖性功能尚未在癌症中直接在体内进行检查。在这里，我们报告，FAK支架功能的破坏，通过其Pro-878/881基序抑制乳腺肿瘤的生长和转移，在一个良好的特点，人类乳腺癌的小鼠模型。内源性FAK基因中的P878 A/P881 A突变降低了突变小鼠来源的肿瘤中上皮-间质转化（EMT）和乳腺癌干细胞（MaCSC）活性标志物的表达。这种突变破坏了FAK支架介导Src在Tyr-315处的内亲和素A2磷酸化的功能，导致MT 1-MMP的表面表达降低，如先前在体外转化的成纤维细胞中观察到的。通过Y315 F内亲和素A2突变体或MT 1-MMP敲低抑制该FAK支架功能的下游组分减少了EMT和MaCSC活性的标记物。相反，使用磷酸化模拟突变体Y315 E内啡肽A2或内啡肽A2敲低绕过支架功能挽救了EMT和MaCSC的标记物以及携带P878 A/P881 A突变的肿瘤细胞中MT 1-MMP的表面表达的减少。总之，这些结果确定了FAK支架功能在乳腺癌中的新作用，其可以作为与激酶抑制相结合的新靶点，用于更有效的治疗策略。
Tyrosine kinases have been shown to play critical roles in cancer development and progression, and their inhibitors hold the potential as effective targeted therapies for breast and other cancers. However, some of these kinases like focal adhesion kinase (FAK) also possess scaffolding functions in intracellular signaling, but such kinase-independent functions of FAK or other kinases have not been examined in cancer directly in vivo. Here, we report that disruption of the function of FAK scaffolding through its Pro-878/881 motif suppressed mammary tumor growth and metastasis in a well characterized murine model of human breast cancer. P878A/P881A mutation in the endogenous FAK gene decreased the expression of markers for epithelial-mesenchymal transition (EMT) and mammary cancer stem cell (MaCSC) activities in tumors derived from mutant mice. This mutation disrupted the function of FAK scaffolding to mediate endophilin A2 phosphorylation at Tyr-315 by Src, leading to the decreased surface expression of MT1-MMP, as observed previously in transformed fibroblasts in vitro. Inhibition of the downstream components of this FAK scaffolding function by Y315F endophilin A2 mutant or MT1-MMP knockdown reduced markers for EMT and MaCSC activities. Conversely, bypass of the scaffolding function using the phosphorylation mimic mutant Y315E endophilin A2 or endophilin A2 knockdown rescued the decreased markers for EMT and MaCSCs as well as surface expression of MT1-MMP in tumor cells harboring the P878A/P881A mutation. Together, these results identify a novel role of FAK scaffolding function in breast cancer, which could serve as a new target in combination with kinase inhibition for more effective treatment strategies.