Tyrosine phosphorylation of transcriptional coactivator WW‐domain binding protein 2 regulates estrogen receptor α function in breast cancer via the Wnt pathway

• Published in: The FASEB journal Vol. 25; no. 9; pp. 3004 - 3018
• Main Authors: Lim, Shen Kiat, Orhant‐Prioux, Magali, Toy, Weiyi, Tan, Kah Yap, Lim, Yoon Pin
• Format: Journal Article
• Language: English
• Published: United States 01-09-2011
• Subjects: Animals; Antineoplastic Agents; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line; crosstalk; EGFR; ERα; Estrogen Receptor alpha - genetics; Estrogen Receptor alpha - metabolism; Female; Gene Expression Regulation, Neoplastic - physiology; Genes, src; Humans; Mammary Neoplasms, Animal - metabolism; Mice; Mice, Nude; Mutation; Neoplasms, Experimental - metabolism; Phosphorylation; Proto-Oncogene Proteins c-yes; Tyrosine - metabolism; WBP2; Wnt Proteins - genetics; Wnt Proteins - metabolism; β‐catenin
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.10-169136

ABSTRACT
WW‐binding protein 2 (WBP2) has been demonstrated in different studies to be a tyrosine kinase substrate, to activate estrogen receptor a (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.—Lim, S. K., Orhant‐Prioux, M., Toy, W., Tan, K. Y., Lim, Y. P. Tyrosine phosphorylation of transcriptional coactivator WW‐domain binding protein 2 regulates estrogen receptor a function in breast cancer via the Wnt pathway. FASEB J. 25, 3004–3018 (2011). www.fasebj.org