SOX9 Promotes Gefitinib Resistance in Non-Small Cell Lung Carcinoma Through Differential Expression of Epithelial to Mesenchymal Transition Markers

Abstract

and women worldwide. The epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), including gefitinib are the most commonly used treatment option for lung cancer. Unfortunately, development of resistance to these EGFR-TKIs within a few months of treatment is the major drawback to lung cancer therapy. Sex-determining region Y-box containing gene 9 (SOX9) plays an important role in cell proliferation, differentiation, cell cycle, and apoptosis in non-small cell lung carcinoma (NSCLC), but its roles in development of EGFR-TKIs resistance in NSCLC cells remains unclear. Epithelial to mesenchymal transition (EMT) favours the cancer cells to escape from drug exposure, thereby development of resistance to drug treatment. Therefore, our aim of the present study was to elucidate the role of SOX9 in the development of resistance to gefitinib in NSCLC cells through EMT pathways. Initially, we measured the expression of SOX9 in normal and gefitinib resistant NSCLC cells (A549 & NCI-H522). Additionally, we performed MTT assay, colony-forming assay, in-vitro scratch motility assay, Annexin-V/FITC apoptosis assay, drug efflux assay, real-time PCR, and western blot analysis. Our findings suggested high SOX9 expression in gefitinib resistant NSCLC cells compared to normal control NSCLC cells. Silencing of SOX9 by siRNA can again sensitize resistant NSCLC cells to gefitinib. Furthermore, we found that SOX9 silencing reduced the colony-forming ability, migration ability, and drug efflux ability, thereby enhanced apoptosis of gefitinib resistance NSCLC cells. In addition, upregulation of SOX9 results downregulation of epithelial markers in association with enhanced expression of the mesenchymal markers in gefitinib resistance NSCLC cells. However, suppression of SOX9 via siSOX9 treatment reversed the epithelial to mesenchymal transition mediated resistance in NSCLC cells. Concerning these results, we conclude that SOX9 regulates sensitivity to gefitinib in NSCLC cells via differential