✓ Aberrant methylation at the promoter region of RASSF1A and GADD45β inversely correlates with protein expression and is linked to the acquisition of TKI resistance in lung cancer cells.✓ Cell treatment with 5-Aza-CdR could partially restore the sensitivity of cells to EGFR-TKI. The gene discussed is RASSF1; the disease is lung carcinoma.