title: AIB1 is required for the acquisition of epithelial growth factor receptor-mediated tamoxifen resistance in breast cancer cells.
abstract: Acquired resistance to tamoxifen has become a serious obstacle in breast cancer treatment. The underlying mechanism responsible for this condition has not been completely elucidated. In this study, a tamoxifen-resistant (Tam-R) MCF-7 breast cancer cell line was developed to mimic the occurrence of acquired tamoxifen resistance as seen in clinical practice. Increased expression levels of HER1, HER2 and the estrogen receptor (ER)-AIB1 complex were found in tamoxifen-resistant cells. EGF stimulation and gefitinib inhibition experiments further demonstrated that HER1/HER2 signaling and AIB1 were involved in the proliferation of cells that had acquired Tam resistance. However, when AIB1 was silenced with AIB1-siRNA in Tam-R cells, the cell growth stimulated by the HER1/HER2 signaling pathway was significantly reduced, and the cells were again found to be inhibited by tamoxifen. These results suggest that the AIB1 protein could be a limiting factor in the HER1/HER2-mediated hormone-independent growth of Tam-R cells. Thus, AIB1 may be a new therapeutic target, and the removal of AIB1 may decrease the crosstalk between ER and the HER1/HER2 pathway, resulting in the restoration of tamoxifen sensitivity in tamoxifen-resistant cells.
authors.affiliation: Department of Medical Oncology, Tumor Hospital of Harbin Medical University, Harbin 150040, China.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Zhao
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Zhang
authors.forename: Xinmei
authors.initials: X
authors.lastname: Kang
authors.forename: Shi
authors.initials: S
authors.lastname: Jin
authors.forename: Changjie
authors.initials: C
authors.lastname: Lou
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D056921:Nuclear Receptor Coactivator 3; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D066246:ErbB Receptors; D056921:Nuclear Receptor Coactivator 3; D018719:Erb-b2 Receptor Tyrosine Kinases; D013629:Tamoxifen; D014157:Transcription Factors; C512478:EGFR protein, human; C508053:ERBB2 protein, human