DNA Promoter Methylation In The Effect Of Spleen Tyrosine Kinase (Syk) Gene Expression In The Lung Cancer

Object:To investigate the expression of Syk mRNA in human lung cancer cell:NL9980, L9981,A549,YTMLC-9 and NCI-H446.To make clear the expression of Syk in the lung cancer and the normal lung tissues.To investigate whether the cell lines of NL9980,L9981,A549,YTMLC-9 and NCI-H446 exist the Syk gene promoter methylation.To investigate the contribution of Syk gene promoter methylation to the expression of Syk in the lung cancer.Methods:Culture the human lung cancer cell lines NL9980,L9981,A549,YTMLC-9, NCI-H446 and the human breast cancer cell lines MCF-7(Syk expression positive), MDA-MB-435S(Syk expression negative) in vitro.Extract the RNA and reverse transcripted the RNA to cDNA,then detected the expression of Syk gene using the Real-time polymerase chain reaction(Real-time PCR).At the same time,16 lung cancer patients(tumor tissues and adjacent normal lung tissues) was detected.Used methylation-specific polymerase chain reaction(MSP) to detected whether the Syk gene promoter methylation is exist in the human lung cancer cell lines, including NL9980,L9981,A549,YTMLC-9,NCI-H446.Used the human breast cancer cell lines MDA-MB-435S(Syk promoter methylation positive),MCF-7(Syk promoter methylation negative) for controls.To deal with them with DNA methyltransferase inhibitor(5-aza-CdR).At last,detected the different of Syk gene expression than use the drug before.Result:Compared with the MCF-7(Syk expression positive) and MDA-MB-435S(Syk epression negative),all the 5 human lung cancer cell lines didn't develop the Syk expression(P＜0.05).In the 16 lung patients,Syk expression was lower in the tumor tissues than adjacent normal lung tissues(P＜0.05). Compared with the MDA-MB-435S(Syk promoter methylation positive) and MCF-7(Syk promoter methylation negative),four in five kinds of Syk gene negative expression cell lines including NL9980,L9981,A549,YTMLC-9 existed the Syk gene promoter methylation,except NCI-H446.We found that the reexpression of Syk when use the 5-aza-CdR in the 4 methylation positive lung cell lines(P＜0.05).Conclusion:Reduced or lost of Syk mRNA may correlate to oncogenesis and growth in lung cancer.Syk may be a candidate tumor suppressor in lung cancer.DNA promoter methylation may be one reason correlative with gene low expression of Syk in the human lung cancer.