Studies have shown that compared with other NSCLC cell lines with the methylated EGFR promoter region, NSCLC cell lines with the unmethylated EGFR promoter region are more sensitive to gefitinib, indicating that EGFR promoter methylation is a potential mechanism of acquired resistance.410 Aberrant methylation of gamma-aminobutyric acid type B receptor subunit 2 (GABBR2) can be seen in erlotinib-treated NSCLC cell lines, which leads to its overexpression. This evidence concerns the gene GABBR2 and non-small cell lung carcinoma.