Abstract 625: Transcription factor slug conferring resistance To EGFR tyrosine kinase inhibitor gefitinib

Abstract

Abstract Purpose: Somatic EGFR mutations of non-small cell lung cancer (NSCLC) are reported to be associated with clinical responsiveness to tyrosine kinase inhibitor gefitinib. Despite the dramatic responses to gefitinib, most patients ultimately have a relapse. The underlying mechanism of the drug resistance is not well clear. Recently, many studies have shown that epithelial to mesenchymal transition (EMT) is involved in resistance to gefitinib in EGFR. Zinc finger transcription factor slug is one of the EMT regulators. In this study, we will investigate whether the slug plays a role in the gefitinib resistance. Materials and Methods: PC9/IR (gefitinib-resistant cell line) was isolated from PC9 (gefitinib-sensitive cell line) after long-term treatment of gefitinib. To identify the factors involved in gefitinib resistance, we analyzed the expression levels of EMT regulators (Slug, Snail, Twist, Zeb-1) in PC9/IR and PC9 cells using quantitative real time PCR and western blot. To investigate the association of Slug and gefitinib-induced resistance, we also engineered to stably express Slug and short hairpin RNA targeting Slug transcript in PC9 and PC9/IR, respectively. Results: The findings showed that mRNA and protein levels of Slug obviously increased in PC9/IR comparing with PC9 and expression of other EMT regulators Snail, Twist, Zeb-1 were similar between these two cell lines. After gefitinib treatment, PC9/IR expressing shRNA against Slug underwent apoptosis and activation of the intrinsic apoptosis pathway. Ectopic expression of Slug protected PC9 cells from undergoing apoptosis in response to gefitinib treatment. Knockdown the expression of slug reversed gefitinib resistance of PC9/IR cells by restoring Bim expression. Conclusions: These results suggest that expression of slug may contribute to resistance to gefitinib in PC9/IR and may be a useful target for treatment of resistance to EGFR tyrosine kinase inhibitor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 625.