title: Association of the breast cancer antiestrogen resistance protein 1 (BCAR1) and BCAR3 scaffolding proteins in cell signaling and antiestrogen resistance.
abstract: Most breast cancers are estrogen receptor-positive and treated with antiestrogens, but aberrant signaling networks can induce drug resistance. One of these networks involves the scaffolding protein BCAR1/p130CAS, which regulates cell growth and migration/invasion. A less investigated scaffolding protein that also confers antiestrogen resistance is the SH2 domain-containing protein BCAR3. BCAR1 and BCAR3 bind tightly to each other through their C-terminal domains, thus potentially connecting their associated signaling networks. However, recent studies using BCAR1 and BCAR3 interaction mutants concluded that association between the two proteins is not critical for many of their interrelated activities regulating breast cancer malignancy. We report that these previously used BCAR mutations fail to cause adequate loss-of-function of the complex. By using structure-based BCAR1 and BCAR3 mutants that lack the ability to interact, we show that BCAR3-induced antiestrogen resistance in MCF7 breast cancer cells critically depends on its ability to bind BCAR1. Interaction with BCAR3 increases the levels of phosphorylated BCAR1, ultimately potentiating BCAR1-dependent antiestrogen resistance. Furthermore, antiestrogen resistance in cells overexpressing BCAR1/BCAR3 correlates with increased ERK1/2 activity. Inhibiting ERK1/2 through overexpression of the regulatory protein PEA15 negates the resistance, revealing a key role for ERK1/2 in BCAR1/BCAR3-induced antiestrogen resistance. Reverse-phase protein array data show that PEA15 levels in invasive breast cancers correlate with patient survival, suggesting that PEA15 can override ERK1/2 activation by BCAR1/BCAR3 and other upstream regulators. We further uncovered that the BCAR3-related NSP3 can also promote antiestrogen resistance. Thus, strategies to disrupt BCAR1-BCAR3/NSP3 complexes and associated signaling networks could ultimately lead to new breast cancer therapies.
authors.affiliation: Sanford-Burnham Medical Research Institute, La Jolla, California 92037.
authors.forename: Yann
authors.initials: Y
authors.lastname: Wallez
authors.affiliation: Sanford-Burnham Medical Research Institute, La Jolla, California 92037.
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Riedl
authors.affiliation: Sanford-Burnham Medical Research Institute, La Jolla, California 92037; Department of Pathology, University of California, San Diego California 92093. Electronic address: elenap@sanfordburnham.org.
authors.forename: Elena B
authors.initials: EB
authors.lastname: Pasquale
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D050719:Crk-Associated Substrate Protein / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020662:Guanine Nucleotide Exchange Factors; D057809:HEK293 Cells; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D061986:MCF-7 Cells; D008856:Microscopy, Fluorescence; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C493841:BCAR1 protein, human; C118588:BCAR3 protein, human; D050719:Crk-Associated Substrate Protein; D020847:Estrogen Receptor Modulators; D004967:Estrogens; D020662:Guanine Nucleotide Exchange Factors; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Anticancer Drug; Breast Cancer; Cancer; Drug Resistance; ERK1/2; MAP Kinases (MAPKs); Mesenchymal Phenotype; NSP3; PEA15; Protein-Protein Interactions