hMLH1 promoter hypermethylation correlates with platinum-resistance in non-small cell lung cancer cells / 中国癌症杂志

ABSTRACT

Background and purpose:hMLH1 promoter methylation is one of the factors in the development of lung cancer.However,little is known about hMLH1 promoter methylation in association with chemotherapy resistance in lung cancer cells.This study aimed to investigate whether resistance to DDP can be overcame by restoring the expression of hMLH1 in A549/DDP cells after treatment with a demethylating agent,5-Aza-2'-deoxycytidine (5-Aza-CdR).Methods:hMLH1 mRNA was determined by RT-PCR in A549,A549/DDP and A549/DDP treated with 5-Aza-CdR;MSP was carried out to determine the methylation status of hMLH1 in A549 and A549/DDP,A549/DDP treated with 5-Aza-CdR.MTT test,Hoechst 33258 staining and flow cytometry were used to determine the change of cell proliferation,apoptotic morphology and the cell apoptosis index,respectively.Results:hMLH1 mRNA was expressed higher in A549 than in A549/DDP.The unmethylation status of hMLH1 was observed in A549 cells whereas partial methylation status of hMLH1 in A549/DDP cells.After treatment with 5-Aza-CdR,the A549/DDP cells displayed an unmethylation of the hMLH1 gene.After the treatment with cisplatin,the IC50 of A549,A549/DDP and A549/DDP treated by 5-Aza-CdR were (4.7?0.7),(30.1?1.8) and (6.9?0.6)?mol/L,respectively.Apoptotic bodies were less in A549/DDP cells than in A549/DDP cells treated with the 5-Aza-CdR.The rate of apoptosis of A549/DDP treated by 5-Aza-CdR was higher than that of A549/DDP.Conclusion:The methylation of hMLH1 may be relevant to the resistance to platinum-based chemotherapy in the A549/DDP cell line.5-Aza-CdR can inhibit hMLH1 methylation,restore the expression of hMLH1,and enhance cell apoptosis as well as the inhibition of cell proliferation of A549/DDP cells after the treatment of cisplatin.