Abstract 4663: Acquired resistance to gefitinib is associated with cancer stem-like phenotype and EMT in EGFR mutant lung adenocarcinoma.

Abstract

Abstract Background: Mutations in the epidermal growth factor receptor (EGFR) gene are associated with increased sensitivity of lung adenocarcinoma to tyrosine kinase inhibitor (TKI) such as gefitinib. During gefitinib treatment, however, the tumor becomes resistant by acquiring specific types of resistance via the somatic changes. Although the underlying mechanisms for acquired resistance include the amplification of c-Met gene and the secondary mutation in EGFR genes, there are still unknown mechanisms that cannot be explained by the two types of genetic changes. Here, we sought to find a novel mechanism to explain TKI-resistance of EGFR-dependent lung adenocarcinoma. Methods: We developed resistant cells (HCC827-GR) from gefitinib-sensitive HCC827 cells harboring EGFR deletion mutation by chronic exposure to increasing concentrations of gefitinib. Acquired resistance mechanisms of HCC827-GR cells were analyzed. Results: HCC827-GR showed much less phosphorylation of most receptor kinases including EGFR but higher phosphorylation of downstream signaling molecules, Erk and Akt, than its parental cell. By comparing the gene expression profiles between HCC827 and HCC827-GR, we found that cancer stem cell (CSC) markers, CD44 and ALDH1A1 genes, were highly induced in HCC827-GR compared with those in HCC827. Knockdown of CD44 and ALDH1A1 expression by RNA interference induced inactivation of both Akt and Erk phosphorylation in HCC827-GR. Furthermore, HCC827-GR displayed CSC-like functionality such as colony formation and the phenotype of epithelial-mesenchymal transition (EMT). Higher level of vimentin, ZEB1 and ZFHX4 and lower level of E-cadherin were observed in HCC827-GR together with morphological change. Interestingly, miR200c, a tumor suppressive microRNA, was dramatically decreased in HCC827-GR. Forced expression of miR200c in HCC827-GR abrogated the increased expression of ZEB1 and ALDH1A1, resulting in the restoration of E-cadherin. Conclusions: These findings imply that cancer stemness induced via CD44 and ALDH1A1 expression and EMT contribute to the acquisition of gefitinib resistance in EGFR-TKI sensitive lung adenocarcinoma. Therefore, CSC markers including CD44 and ALDH1A1 and EMT regulators such as miR200c can be used as therapeutic targets for TKI-resistant EGFR-dependent lung adenocarcinoma. Citation Format: Sun Min Lim, Hyun Jung Kim, Young Ho Ban, Sang Jun Ha, Byoung Chul Cho. Acquired resistance to gefitinib is associated with cancer stem-like phenotype and EMT in EGFR mutant lung adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4663. doi:10.1158/1538-7445.AM2013-4663 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.