小干扰RNA沉默人乳头瘤病毒16E6基因对子宫颈癌SiHa细胞系中E-钙黏蛋白表达及高甲基化的影响

The effect of human papfllomavirus 16 E6 gene silenced by small interfering RNA on the expression and the promoter hypermethylation status of E-cadherin in cervical cancer SiHa cell line

目的研究小干扰RNA（siRNA）沉默人乳头瘤病毒（HPV）16E6基因对子宫颈癌SiHa细胞系中E-钙黏蛋白（E—cad）表达及其基因启动子区高甲基化的影响。方法运用以慢病毒为载体质粒的siRNA沉默子宫颈癌SiHa细胞系中HPV16E6基因。采用实时荧光定量聚合酶链反应（RT．qPCR）法及蛋白质印迹法（Westernblot）分别检测沉默后SiHa细胞中HPVl6E6mRNA表达水平、EcadmRNA及蛋白表达水平。用甲基化特异性PCR（MSP）法检测SiHa细胞系中E—cad基因（CDH1）启动子区甲基化情况。结果siRNAE6组、空载体组、空白对照组E—cadmRNA相对表达量分别为4．755±1．085、1．224±0．840、1．327±1．221，蛋白相对表达量分别为0．616±0．019、0．325±0．016、0．299±0．015，其中siRNAE6组SiHa细胞中E—cadmRNA及蛋白相对表达量明显高于另两组，差异均有统计学意义（F=21．346，P〈0．01；F=323．398，P〈0．01），而空载体组和空白对照组之间差异无统计学意义（P〉0．05）。与HPV16E6基因沉默前E．cad完全甲基化状态相比较，沉默后E．cad基因甲基化扩增产物呈弱阳性，其强度较空载体组及空白对照组明显减弱，而非甲基化扩增呈阳性。结论HPV16E6基因沉默可使子宫颈癌SiHa细胞中E．cad表达上调，同时能够降低CDH1基因启动子区高甲基化水平，可能在一定程度上扭转CDH1基因启动子区的高甲基化状态，引起E-cad重新表达。

Objective To investigate the influence of human papillomavims （HPV） 15 E5 gene silencing by small interfering RNA （siRNA） on the expression and the promoter hypermethylation status of E-cadherin （E-cad） in cervical cancer SiHa cell line. Methods siRNA which used lentivirus as the vector was used to knock down the HPV16E6 gene in cervical cancer SiHa cell line. The expression levels of HPV15E5 mRNA, E-cad mRNA and protein in siRNA-HPV15E6 SiHa cell line were detected by RT-qPCR and Western blot, respectively. Methylation specific PCR （MSP） method was used to detect the methylation status of E-cad gene （CDH1） promoter in siRNA-HPV15E6 SiHa cell line. Results The E-cad mRNA expression levels in siRNA E5 group, empty vector group and blank control group were 4.755±l.085, 1.224±0.840, 1.327±.221, respectively. The protein expression levels were 0.616±0.019, 0.325±0.016, 0.299-±0.015, respectively. The expressions of E-cad mRNA and protein in siRNA E5 group were significantly higher than those in the empty vector group and blank control group （F = 21.346, P 〈 0.01; F = 323.398, P 〈 0.01）, and the difference between the empty vector group and blank control group was not statistically significant （P 〉 0.05）. After knocking down HPV15E6 gene, the methylation status of E-cad gene was weakly positive, and the intensity of the amplified products was significantly weaker than that in the empty vector group and blank control group, while the unmethylation amplification was positive. Conclusions Knocking down the HPV16E6 gene increases the expression of E-cad in cervical cancer SiHa cell line, and decreases the level of CDH1 promoter methylation. To a certain extent, it partly reverses the hypermethylation status of CDH1 promoter, and causes E-cad to be re-expressed.