Estrogen Receptor β Is Involved in Acquired Resistance to EGFR-tyrosine Kinase Inhibitors in Lung Cancer.

BACKGROUND/AIM:Acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) has posed serious clinical problems in the treatment of lung adenocarcinoma (LADC) patients harboring relevant EGFR mutations. In this study, we explored the role of estrogen receptor β (ERβ) in the development of acquired resistance to EGFR-TKIs in human LADC. MATERIALS AND METHODS:First, the role of ERβ in erlotinib resistance of LADC cell lines (PC9/ER) was examined. Then, the immunolocalization of ERβ in 28 LADC patient samples treated with EGFR-TKIs was investigated. RESULTS:Cytoplasmic ERβ was upregulated in erlotinib resistant cell lines. EGFR-TKIs sensitivity increased with ERβ inhibition in PC9/ER cells. ERK1/2 and AKT activities were both markedly increased by specific ERβ agonists even under erlotinib treatment of PC9/ER cells. Cytoplasmic ERβ immunoreactivity was significantly associated with clinical response to EGFR-TKIs. CONCLUSION:Cytoplasmic ERβ in LADC cells was involved in the development of resistance to EGFR-TKIs.