| Summary: | 博士 === 國防醫學院 === 醫學科學研究所 === 99 === Rationale: Non-small cell lung cancers carrying epidermal growth factor receptor (EGFR) mutations respond well to EGFR tyrosine kinase inhibitors (TKIs), but patients ultimately develop drug resistance and relapse. Although epithelial-mesenchymal transition (EMT) can predict resistance to EGFR TKIs, the molecular mechanisms are still unknown.
Objectives: To examine the role of EMT regulators in resistance to gefitinib.
Methods: The expression level of EMT regulators in gefitinib-sensitive cells (PC9) and gefitinib-resistant cells (PC9/gef) was determined using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. Molecular manipulations (silencing or overexpression) were performed to investigate the effects of EMT regulators on gefitinib resistance in vitro, and a xenograft mouse model was used for in vivo confirmation. In addition, cancer cells from fifty-four patients with malignant pleural effusions of lung adenocarcinoma were collected for analysis of EMT regulator mRNA by quantitative real-time RT-PCR.
Results: Slug expression, but not that of snail, twist or zeb-1, was significantly increased in PC9/gef compared to PC9 cells. Slug knockdown in PC9/gef cells reversed resistance to gefitinib, and overexpression of Slug in PC9 cells protected cells from gefitinib induced-apoptosis. Silencing of Slug in gefitinib-resistant cells restored gefitinib-induced apoptosis primarily through Bim upregulation and activation of caspase-9. Slug enhanced tumor growth in a xenograft mouse model, even with gefitinib treatment. In clinical samples, Slug expression was significantly higher in cancer cells with resistance to EGFR TKIs than in treatment-naïve cancer cells.
Conclusions: Slug contributes to the resistance to gefitinib and may be a potential therapeutic target for treating resistance to EGFR TKIs.
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