Correlation between DAPK Promoter Methylation and Gefitinib Sensitivity in Non-small Cell Lung Cancer

Objective: To explore the correlation between DAPK promoter methylation and gefitinib sensitivity in human non-small cell lung cancer (NSCLC). Methods: Different concentrations of gefitinib were respectively used to act on two strains of NSCLC cells with epidermal growth factor receptor (EGFR) exon 19-deleted mutation (H1650 and PC9) and two strains with wild-type EGFR (A549 and H520). The cells were detected before and after 5-aza-CdR demethylation. The cell proliferation rate was determined by CCK-8 assay, apoptosis rate by flow cytometry (FCM), DAPK mRNA expression by fluorescent quatititive polymerase chain reaction (RT-PCR), and methylation status in the region of DAPK promoter by methylation-specific PCR. Results: Gefitinib had proliferation inhibition effects on four kinds of cell lines by varying degrees, and with its concentration increase, the proliferation of PC9 and A549 cells was inhibited obviously, whereas both H1650 and H520 cells presented drug-resistance. After 5-aza-CdR methylation, the sensitivity of H1650 cells with EGFR mutation and H520 cells with wild-type EGFR to gefitinib was enhanced compared with the previous. Among the cell lines not dealt with 5-aza-CdR, the gefitinib-sensitive cell lines PC9 and A549 displayed high expression of DAPK, with the gene promoter in a non-methylation status, but in gefitinib-resistant cell lines H1650 and H520, DAPK expression was low, with DAPK promoter in a high methylation status. DAPK gene expression and gefitinib sensitivity in H1650 and H520 cell lines apparently were increased compared to the previous after 5-aza-CdR was applied to remove the methylation of DAPK gene promoter region in gefitinib-non-sensitive cell lines H1650 and H520, with significant difference (P < 0.01). However, there were no significant changes in gefitinib-sensitive cell lines PC9 and A549 (P > 0.05). Conclusion: High methylation in the region of tumor suppressor gene DAPK promoter can reduce the sensitivity of gefitinib to NSCLC by down-regulating DAPK gene expression. Detecting the methylation status of DAPK gene may provide a new method for predicting the efficiency of gefitinib