The first suggestion of a correlation between DNA methylation of GABBR2 and resistance to TKI erlotinib in NSCLC patients comes from the study by Niu X et al. who investigated the variations of methylation patterns by whole-genome DNA high-throughput assays in a small cohort of NSCLC patients under erlotinib treatment (47). The gene discussed is GABBR2; the disease is non-small cell lung carcinoma.