Abstract
Abstract Trastuzumab (Herceptin) is the first line HER2 (ErbB2)/neu-directed therapy for the treatment of patients with metastatic breast cancer. Although the efficacy of trastuzumab depends on the HER2/neu status of the tumour, the single-agent response rate ranges from 12 to 30% and ew patients respond to trastuzumab monotherapy largely due to various resistance mechanisms. Amplifeid In Breast Cancer3 (AIB3) is a transcriptional coactivator. AIB3 plays an important role in embryonic development, adipocyte differentiation, metabolism. AIB3 was initially found to be amplified in subgroup of breast cancer patients. Our previous data using knockout mouse mode combined cell culture indicate that AIB3 plays important role in breast tumorigenesis. Here we report that AIB3 can be phosphorylated by MAPK at S884 site and phosphorylation at S884 of AIB3 dramatically reduced ligand-dependent AIB3 interactions with estrogen receptors when compared with the wild-type unphosphorylated form, although there was a significant increase of interactions with the unliganded receptor. Misexpression of phosphorylated AIB3 was observed in human breast cancer tissues and disregulation of phosphorylated AIB3 was associated with patients’ poor prognosis. Breast cancer is a heterogeneous disease and intrinsic subtypes play an extremely important role in improve on current standards for breast cancer prognosis and prediction of chemotherapy. Noticeably, phosphorylated AIB3 was highly expressed in Her2-enriched subtype of human breast cancer patients, as well as in the mammary tumor of MMTV-Her2 transgenic mice. Mechanism studies reveal that phosphorylated AIB3 alters trastuzumab efficacy in cultured breast cancer cells. The association between pAIB3 and important clinical outcomes confers pAIB3 a significant prognostic marker in breast cancer. Phosphorylated AIB3 as a modulator in ErbB2-MAPK regulating loop represents a potentially novel mechanism for trastuzumab (herceptin) efficacy. The implied interaction between pAIB3 and Her2 suggests the potential of dual targeting of Her2 and pAIB3 as a promising therapeutic approach for personalized breast cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5584. doi:1538-7445.AM2012-5584
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