title: Function of focal adhesion kinase scaffolding to mediate endophilin A2 phosphorylation promotes epithelial-mesenchymal transition and mammary cancer stem cell activities in vivo.
abstract: 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.
authors.affiliation: Division of Molecular Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.
authors.forename: Huaping
authors.initials: H
authors.lastname: Fan
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhao
authors.forename: Shaogang
authors.initials: S
authors.lastname: Sun
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.forename: Jun-Lin
authors.initials: JL
authors.lastname: Guan
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000556:secondary; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology* / Q000473:pathology*; D053511:Matrix Metalloproteinase 14 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000201:enzymology* / Q000473:pathology*; D010766:Phosphorylation; D011485:Protein Binding; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology; D013489:Suppression, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D014408:Biomarkers, Tumor; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase; D051417:Focal Adhesion Kinase 1; C496051:Ptk2 protein, mouse; D053511:Matrix Metalloproteinase 14