Gao Jun, Wang Lihua, Xu Jinkang, Zheng Jianming, Man Xiaohua, Wu Hongyu, Jin Jin, Wang Kaixuan, Xiao Huasheng, Li Shude, Li Zhaoshen
J Exp Clin Cancer Res. 2013 Nov 5;32(1):86. doi: 10.1186/1756-9966-32-86.
Altered gene methylation, regulated by DNA methyltransferases (DNMT) 1, 3a and 3b, contributes to tumorigenesis. However, the role of DNMT in pancreatic ductal adenocarcinoma (PDAC) remains unknown.
Expression of DNMT 1, 3a and 3b was detected in 88 Pancreatic ductal adenocarcinoma (PDAC) and 10 normal tissue samples by immunohistochemistry. Changes in cell viability, cell cycle distribution, and apoptosis of PDAC cell lines (Panc-1 and SW1990) were assessed after transfection with DNMT1 and 3b siRNA. Levels of CDKN1A, Bcl-2 and Bax mRNA were assessed by qRT-PCR, and methylation of the Bax gene promoter was assayed by methylation-specific PCR (MSP).
DNMT1, 3a and 3b proteins were expressed in 46.6%, 23.9%, and 77.3% of PDAC tissues, respectively, but were not expressed in normal pancreatic tissues. There was a co-presence of DNMT3a and DNMT3b expression and an association of DNMT1 expression with alcohol consumption and poor overall survival. Moreover, knockdown of DNMT1 and DNMT3b expression significantly inhibited PDAC cell viability, decreased S-phase but increased G1-phase of the cell cycle, and induced apoptosis. Molecularly, expression of CDKN1A and Bax mRNA was upregulated, and the Bax gene promoter was demethylated. However, a synergistic effect of combined DNMT1 and 3b knockdown was not observed.
Expression of DNMT1, 3a and 3b proteins is increased in PDAC tissues, and DNMT1 expression is associated with poor prognosis of patients. Knockdown of DNMT1 and 3b expression arrests tumor cells at the G1 phase of the cell cycle and induces apoptosis. The data suggest that DNMT knockdown may be a novel treatment strategy for PDAC.
由DNA甲基转移酶（DNMT）1、3a和3b调控的基因甲基化改变有助于肿瘤发生。然而，DNMT在胰腺导管腺癌（PDAC）中的作用仍不清楚。
通过免疫组织化学检测88例胰腺导管腺癌（PDAC）和10例正常组织样本中DNMT 1、3a和3b的表达。用DNMT1和3b小干扰RNA转染后，评估PDAC细胞系（Panc-1和SW1990）的细胞活力、细胞周期分布和凋亡变化。通过qRT-PCR评估CDKN1A、Bcl-2和Bax mRNA水平，通过甲基化特异性PCR（MSP）检测Bax基因启动子的甲基化。
DNMT1、3a和3b蛋白分别在46.6%、23.9%和77.3%的PDAC组织中表达，但在正常胰腺组织中不表达。DNMT3a和DNMT3b表达共同存在，且DNMT1表达与饮酒和总体生存率差有关。此外，DNMT1和DNMT3b表达的敲低显著抑制了PDAC细胞活力，减少了细胞周期的S期但增加了G1期，并诱导了凋亡。在分子水平上，CDKN1A和Bax mRNA的表达上调，且Bax基因启动子去甲基化。然而，未观察到DNMT1和3b联合敲低的协同效应。
DNMT1、3a和3b蛋白在PDAC组织中的表达增加，且DNMT1表达与患者预后不良有关。DNMT1和3b表达的敲低使肿瘤细胞停滞在细胞周期的G1期并诱导凋亡。数据表明，DNMT敲低可能是PDAC的一种新的治疗策略。
