Decitabine reverses gefitinib resistance in PC9 lung adenocarcinoma cells by demethylation of RASSF1A and GADD45β promoter.

The acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is the major reason for the failure of target therapy in advanced non small cell lung cancer (NSCLC) patients, the mechanism of which has not been fully elucidated yet. The present study aimed to investigate the different DNA methylation profile before and after acquired EGFR-TKI resistance, and explore the influence of the DNA demethylater, decitabine, on EGFR-TKI resistance. The DNA methylation chip was used to screen the genes whose DNA methylation status were changed in the EGFR-TKI sensitive human NSCLC cell line PC9, and the induced EGFR-TKI resistant NSCLC cell line PC9/GR (harboring T790M mutation). According to the results and literature reports, the tumor suppressor genes, RASSF1A and GADD45β were selected for further research. Methylation specific PCR (MSP) and western blot further confirmed that the promoters of these two genes were methylated, and the protein expressions were significantly inhibited in PC9/GR cells. Additionally, decitabine, the DNA methyl transferase inhibitor, could reverse the methylation status of RASSF1A and GADD45β promoters, elevate protein expression, and partially restore the sensitivity of PC9/GR cells to EGFR-TKI. To conclude, our results suggested that the DNA methylation of RASSF1 and GADD45β may play a role in EGFR-TKI resistance, and epigenetic intervention might be an effective strategy to reverse EGFR-TKI resistance, suggesting further study.