Significance of aberrant expression of DNA methyltransferase 1 in cervical cancerization tissue and cervical cancer cell lines

Abstract

Objective To explore the effects of aberrant expression of DNA methyltransferase 1 (DNMT1) in cervical cancerization tissue and cervical cancer cells.Methods Cervical tissues were collected from 80 cases with a diagnosis of invasive cervix squamous cell carcinoma (SCC),53 cases with high-grade cervical intraepithelial neoplasia (CIN Ⅱ/Ⅲ),52 cases with low-grade cervical intraepithelial neoplasia (CIN Ⅰ)and 53 cases with normal cervix (NC).Meanwhile,Caski (HPV16-positive) and C33A (HPV-negative) cells selected from cervical cancer cell lines were cultured routinely in vitro.The expression of DNMT1 protein and mRNA were examined by Western blot analysis and real-time PCR (qRT-PCR) in the tissues and cells,respectively.Results The levels of DNMT1 protein were 1.33,1.84 and 2.28,and the Ct-ratios (DNMT1/β-actin) of DNMT1 mRNA were 1.27,1.27 and 1.26 in CIN Ⅰ,CIN Ⅱ/Ⅲand SCC group,respectively.Comparing with NC group,the expression of DNMT1 protein or mRNA was elevated in deficient cervical groups,with statistical significance (F =110.57,P ＜ 0.001,F =2.68,P =0.048).The expression levels of DNMT1 protein were increased steadily according to severity of the cervix lesions (x2tend =50.80,P ＜ 0.001),however,the expression of DNMT1 mRNA was not observed the same tendency (x2tend =3.63,P ＞ 0.05).The results from experiment in vitro showed that the levels of DNMT1 protein or mRNA were both higher in Caski cell than in C33A cell,especially for DNMT1 mRNA with significantly difference (t =7.134,P =0.002).Conclusion Aberrant expression of DNMT1 protein or mRNA could link with the risk of cervical cancerization by both transcriptional and posttranscriptional mechanisms.There would be a synergistic effect between overexpression of DNMT1 and HPV16 infection in the progression of cervix carcinogenesis. Key words: DNA methyltransferase 1; Aberrant expression; Cervical cancerization; Cervical cancer cells