title: Tyrosine phosphorylation of transcriptional coactivator WW-domain binding protein 2 regulates estrogen receptor α function in breast cancer via the Wnt pathway.
abstract: WW-binding protein 2 (WBP2) has been demonstrated in different studies to be a tyrosine kinase substrate, to activate estrogen receptor α (ERα)/progesterone receptor (PR) transcription, and to play a role in breast cancer. However, the role of WBP2 tyrosine phosphorylation in regulating ERα function and breast cancer biology is unknown. Here, we established WBP2 as a tyrosine phosphorylation target of estrogen signaling via EGFR crosstalk. Using dominant-negative, constitutively active mutants, RNAi, and pharmacological studies, we demonstrated that phosphorylation of WBP2 at Tyr192 and Tyr231 could be regulated by c-Src and c-Yes kinases. We further showed that abrogating WBP2 phosphorylation impaired >60% of ERα reporter activity, putatively by blocking nuclear entry of WBP2 and its interaction with ERα. Compared to vector control, overexpression of WBP2 and its phospho-mimic mutant in MCF7 cells resulted in larger tumors in mice, induced loss of cell-cell adhesion, and enhanced cell proliferation, anchorage-independent growth, migration, and invasion in both estrogen-dependent and -independent manners, events of which could be substantially abolished by overexpression of the phosphorylation-defective mutant. Hormone independence of cells expressing WBP2 phospho-mimic mutant was associated with heightened ERα and Wnt reporter activities. Wnt/β-catenin inhibitor FH535 blocked phospho-WBP2-mediated cancer cell growth more pronouncedly than tamoxifen and fulvestrant, in part by reducing the expression of ERα. Wnt pathway is likely to be a critical component in WBP2-mediated breast cancer biology.
authors.affiliation: Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Shen Kiat
authors.initials: SK
authors.lastname: Lim
authors.forename: Magali
authors.initials: M
authors.lastname: Orhant-Prioux
authors.forename: Weiyi
authors.initials: W
authors.lastname: Toy
authors.forename: Kah Yap
authors.initials: KY
authors.lastname: Tan
authors.forename: Yoon Pin
authors.initials: YP
authors.lastname: Lim
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D016391:Genes, src; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D009374:Neoplasms, Experimental / Q000378:metabolism*; D010766:Phosphorylation; D051575:Proto-Oncogene Proteins c-yes; D015534:Trans-Activators; D014443:Tyrosine / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D002352:Carrier Proteins; D047628:Estrogen Receptor alpha; D015534:Trans-Activators; C484576:Wbp2 protein, mouse; D051153:Wnt Proteins; D014443:Tyrosine; D051575:Proto-Oncogene Proteins c-yes