Acquired Resistance to EGFR Inhibitors Is Associated with a Manifestation of Stem Cell–like Properties in Cancer Cells

Abstract

Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell–like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell–like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell–like property with EGFR-TKI treatment.

Inhibition of ABCB1 Overcomes Cancer Stem Cell–like Properties and Acquired Resistance to MET Inhibitors in Non–Small Cell Lung Cancer

“…The gene encoding ABCB1 (ATP-binding cassette transporter belonging to subfamily B member 1), which belongs to the ATP-binding cassette transporter family, was among the most upregulated genes in EBC-1R cells (Table 2). ABCB1 has recently been reported to be associated with CSC-like properties (23). We confirmed that the ABCB1 gene was significantly overexpressed in EBC-1R cells by qRT-PCR analysis ( Fig.…”

“…The significance of CSC-like properties has been reported in NSCLC (35,36). EGFR-mutant NSCLC cells exhibited CSClike properties with EMT after the failure of gefitinib treatments (23). We found that EBC-1R cells showed high levels of sphere formation and EMT phenotype.…”

“…Previous studies reported that increased ABCB1 conferred resistance to chemotherapeutic agents in several cancers (31)(32)(33). ABCB1 is also closely correlated with CSC-like properties and is one of the CSC markers (23). Cells with CSC-like properties, which are characterized by the capacity for pluripotency and selfrenewal, have been attracting interest as a source of cancer cells (34).…”

“…2B). The presence of CSC-like properties was closely related to EMT (23). Therefore, we evaluated the expression levels of EMT markers in EBC-1R cells.…”

The role of epithelial to mesenchymal transition in resistance to epidermal growth factor receptor tyrosine kinase inhibitors in non-small cell lung cancer

“…Unfortunately, all patients acquire resistance over time. So far, some resistance mechanisms have been discovered including the T790M secondary mutation in EGFR, MET amplification, FGFR overexpression, IGF1R overexpression, transition to small cell lung carcinoma, gain of cancer stem-cell features, and epithelial to mesenchymal transition (EMT), but much still needs to be revealed (9)(10)(11)(12)(13). Up to 30% of the patients with EGFR mutations experience no objective response to EGFR-TKIs and hence appear as intrinsic resistant (14,15).…”