The Relationship Between The Expression Of DNMT1 And The Methylation Status Of HMSH2 In Non-Small Cell Lung Cancer

Objective:To study DNA methyltransferase 1(DNMT1)mRNA and protein expression and mismatch repair gene hMSH2 protein expression and the state of promoter methylation of hMSH2 gene in the tumor tissues and adjacent tissue specimens of non-small cell lung cancer,and correlation of gene expression,and contact with clinical features.Methods:The samples from surgical specimens,including tumor tissues and adjacenttissue specimens of non-small cell lung cancer which was collected in the Department of thoracic surgery surgically resected and pathologically confirmed collected between 2015-11 and 2016-6,in addition to collect 10 cases of non tumor tissue(including the diagnosis of lungabscess,pneumothorax,hamartoma and lung tissue),all of the tissues were in half an hour inside the box to save the-80?.The collected samples were divided into three parts.Total RNA extracted from cancerous and paracancerous tissues of the first part was reverse-transcribed into cDNA,and the expression of DNMT1 mRNA was tested by Real-time PCR means.Proteins were extracted from the second part and Western Blot was used to detect protein expression of DNMT1,hMSH2.DNA extracted from the last part was performed bisulfite conversion,then methylation specific polymerase chain reaction(MSP)was adopted to analyze promoter methylation status of hMSH2.Analyze the relationship between the expression of DNMT1 mRNA and protein and the expression of hMSH2 protein,meanwhile,explore the correlation between the expression of DNMT1 and the methylation status of hMSH2 and their relationship with clinicopathological features.Result:The expression of DNMT1 mRNA in cancer tissues of 52 NSCLC patients was significantly higher than that in paracancerous tissues(3.1623±0.5125,2.8731±0.3706,P<0.01);The protein expression of DNMT1 in cancer tissues was significantly higher than that in adjacent tissues(0.74±0.30,0.44±0.24,P<0.05).The protein expression of hMSH2 in cancer tissue was significantly lower than that in paracancerous tissue(0.47±0.25,0.73±0.31,P<0.05).The positive rate of methylation of h MSH2 gene promoter in lung cancer tissues was higher than that in adjacent tissues.57.7%(30/52),34.6%(18/52),and this difference was statistically significant(?~2=5.571,P<0.05).The correlation analysis showed that the expression of DNMT1 mRNA and protein were positively correlated with the methylation level of hMSH2 promoter region(r=0.528,P<0.05;r=0.541,P=0.000).There was a significant negative correlation between DNMT1 protein expression and hMSH2 protein expression(r=-0.488,P=0.000).The expression of DNMT1 protein was associated with lymph node metastasis and invasion of surrounding tissues and TNM staging(P?0.05),but not connected with clinicopathological features such as gender,age,tumor size and pathological type(P>0.05).There was no significant correlation between DNMT1 mRNA and clinical pathological features above.The level of methylation of h MSH2 promoter was not significantly related to sex,age,tumor size,pathological type,invasion of surrounding tissue,lymph node metastasis and TNM staging(P>0.05).Conclusion:The high expression of DNMT1 mRNA and protein in NSCLC is positively correlated with the promoter methylation level of hMSH2 gene.The methylation level of hMSH2 promoter region is negatively correlated with its protein level.DNMT1 may regulate the tumor suppressor gene through methylation mechanism,leading to low expression of hMSH2.The expression of those two genes is related to the clinicopathological features of patients with non-small cell lung cancer,and is particularly related to lymph node metastasis and TNM staging.The high expression of DNMT1 mRNA and protein and the methylation of hMSH2 promoter region may be closely related to the occurrence,development,and metastasis of NSCLC,both of which may provide help for lung cancer marker screening and early diagnosis.