We established HCC4006ER (erlotinib-resistant) cells as a model of EMT-related acquired resistance to EGFR-TKIs by chronic exposure of sensitive HCC4006 NSCLC cells containing an EGFR mutation (exon 19; L747-A750del insP) to increasing concentrations of erlotinib. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.