Altered expression of cellular proliferation, apoptosis and the cell cycle-related genes in lung cancer cells with acquired resistance to EGFR tyrosine kinase inhibitors

Non-small cell lung cancers harboring somatic gain-of-function mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase domain respond well to treatment with EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib. However, all patients who experience a marked improvement with these drugs eventually develop disease progression due to the acquisition of drug resistance. Approximately half of the cases with acquired resistance to EGFR TKIs can be accounted for by a second-site mutation in exon 20 of the EGFR kinase domain (T790M). However, the changes of gene expression involved in EGFR TKI resistance due to the T790M mutation remain poorly defined. The present study established lung cancer cell lines that were resistant to gefitinib or erlotinib, and these cell lines were verified to contain the EGFR T790M mutation. The differential expression of genes associated with acquired resistance was verified in the present study by mRNA microarray analysis. Among the genes whose expression was significantly altered, genes whose expression was altered in gefitinib- and erlotinib-resistant cells were focused on. Notably, a total of 1,617 genes were identified as being differentially expressed in gefitinib- and erlotinib-resistant cells. Indeed, Gene ontology analysis revealed altered expression of genes involved in the regulation of cellular proliferation, apoptosis, and the cell cycle in EGFR TKI-resistant cells. The present results demonstrate distinctive gene expression patterns of EGFR TKI-resistant lung cancer cells with the EGFR T790M mutation. The present study can provide key insights into gene expression profiles involved in conferring resistance to EGFR TKI therapy in lung cancer cells.