Abstract: Objective To examine the relationship between EGFR gene promoter methylation and the sensitivity of gefitinib in nonsmall cell lung cancer（NSCLC） cell lines. Methods HCC827, H1650, H1975, H358, H1299 and A549 cells were treated with different dose of gefitinib separately. Cell counting kit8（CCK-8） assay was used to determine the cell proliferation inhibition rate. The protein and mRNA expression levels of EGFR were detected by Western blotting and RTPCR methods. The methylation of EGFR gene promoter region was examined by methylationspecific PCR.
ResultsEGFR mutation status：HCC827 and H1650 cells were exon 19 deletions; H1975 cells were exon 21 L858R point and exon 20 T790M insertion mutations，and H358，H1299，A549 were all wide type cells. According to the 50% inhibition concentration（IC50）, the HCC827 was most sensitive to genfitinib and H538 was moderately sensitive, while H1650 was nonsensitive. H1299 and A549 were less sensitive to genfitinib. The expression of EGFR protein and mRNA were relatively higher in HCC827 and H358 cells comparing with other four cell lines（P＜0.05）. EGFR gene promoter region was unmethylated in HCC827 cells and partly methylated in H358 cells，while in other four cells were all methylated. Conclusion EGFR gene promoter methylation may contribute to the downregulation of EGFR gene and consequently affect the sensitivity of gefitinib in NSCLC cell lines.Analysis of methylation status of EGFR gene promoter may have definite value in predicting the therapeutic response of gefitinib.