乙型肝炎病毒X蛋白通过DNMT3A诱导肝癌细胞RUNX3基因高甲基化

目的研究肝癌细胞中乙型肝炎病毒X蛋白(HBx)对抑癌基因Runt相关转录因子3(RUNX3)表达的影响及相关作用机制,探讨乙肝病毒促肝癌发生的表观遗传调控。方法HBx重组表达载体转染5-aza-CdR处理或未处理的Huh7、HepG2肝癌细胞,Western Blot及RT-qPCR检测RUNX3 的表达,分析RUNX3基因启动子CpG岛甲基化水平。合成DNA甲基转移酶3A的小干扰RNA(siRNA_3A)单独转染或与HBx共转染,检测RUNX3的表达。PCR检测21例手术切除的肝细胞癌新鲜组织标本HBx表达情况,比较HBx阴性与HBx阳性组织样本间RUNX3的表达差异以及启动子甲基化程度。结果过表达HBx可导致肝癌细胞内RUNX3表达下调,且甲基转移酶抑制剂5-aza-CdR可完全阻断HBx对RUNX3的抑制作用。HBx诱导RUNX3基因启动子CpG岛发生高甲基化,但不影响DNA甲基转移酶的表达。siRNA_3A转染肝癌细胞后,RUNX3 mRNA与蛋白表达均显著上调;其与HBx共转染后,逆转了单独HBx对RUNX3的抑制作用。HBx阳性的肝癌组织中RUNX3 mRNA表达水平较HBx阴性组低,且RUNX3启动子甲基化程度也相对较高。结论HBx通过促进RUNX3启动子区域发生高甲基化而抑制其表达,且这一过程是由DNMT3A所介导的。     

Downregulating sCLU Enhances the Sensitivity of Hepatocellular Carcinoma Cells to Gemcitabine by Activating the Intrinsic Apoptosis Pathway

Purpose

The purpose of this study was to investigate whether the therapeutic activity of gemcitabine (GCB) in hepatocellular carcinoma (HCC) could be increased by the down-regulation of secretory clusterin (sCLU), a glycoprotein that is considered to play a cytoprotective role in the resistance to chemotherapy.

Methods

The expression of sCLU was detected in HCC tumor tissues and cell lines. A cell viability and apoptosis assay were performed in parental HCC cells or the same cells transfected with sCLU shRNA and treated with or without GCB. The potential downstream pathways were investigated using the Human Apoptosis RT² Profiler? PCR Array.

Results

The expression levels of sCLU in HCC tissues were significantly higher than in adjacent non-tumor liver tissues and were associated with the histological grade and transarterial chemoembolization. sCLU overexpression was also found in three HCC cell lines and hepatocytes. The depletion of sCLU synergistically increased GCB sensitivity in Bel7402 and SMMC7721 cells and induced cell apoptosis. Based on the PCR array analysis, sCLU depletion also resulted in the up-regulation of BNIP1, GADD45A, TNFRSF10A, and TRADD and down-regulation of AKT1 in Bel7402 and SMMC7721 cells compared with the parental controls. These results were further supported by a Western blot analysis, which showed increased GADD45a protein expression and the decreased expression of phosphorylated AKT. GADD45a overexpression also increased the sensitivity to GCB in the Bel7402 and SMMC7721 cells.

Conclusion

Targeting sCLU may be a useful method to enhance the cytotoxic effect of GCB in hepatocellular carcinoma.     

KISS1 methylation and expression as predictors of disease progression in colorectal cancer patients

AIM:To examine the effect of aberrant methylation of the KISS1 promoter on the development of colorectal cancer(CRC)and to investigate reversing aberrant methylation of the KISS1 promoter as a potential therapeutic target.METHODS:KISS1 promoter methylation,mRNA expression and protein expression were detected by methylation-specific polymerase chain reaction(PCR),real-time quantitative PCR and Western blotting,respectively,in 126 CRC tissues and 142 normal colorectal tissues.Human CRC cells with KISS1 promoter hypermethylation and poor KISS1 expression were treated in vitro with 5-aza-2’-deoxycytidine(5-Aza-CdR).After treatment,KISS1 promoter methylation,KISS1 mRNA and protein expression and cell migration and invasion were evaluated.RESULTS:Hypermethylation of KISS1 occurred frequently in CRC samples(83.1%,105/126),but was infrequent in normal colorectal tissues(6.34%,9/142).Moreover,KISS1 methylation was associated with tumor differentiation,the depth of invasion,lymph node metastasis and distant metastasis(P<0.001).KISS1methylation was also associated with low KISS1 expression(P<0.001).Furthermore,we observed re-expression of the KISS1 gene and decreased cell migration after 5-Aza-CdR treatment in a CRC cell line.CONCLUSION:These data suggest that KISS1 is down-regulated in cancer tissues via promoter hypermethylation and therefore may represent a candidate target for treating metastatic CRC.     

人肝癌细胞系Slit/Robo启动子甲基化状态及基因表达的研究

目的 研究Slit/Robo信号通路相关基因Slit1、Slit2、Slit3和Robo1、Robo3在多种人肝癌细胞系中的表达及甲基化状态,探讨与肝癌发生和发展的关系. 方法提取9种人肝细胞癌细胞株(Hep3B、HepG2、PLC/PRF/5/PRF/5、SMMC-7721、BEL-7402、MHCC97-H,MHCC97-L、LM3、LM6)及对照细胞株L02的基因组DNA和总RNA,采用半定量逆转录聚合酶链反应技术和甲基化特异性聚合酶链反应技术检测Slit1、Slit2,Slit3和Robo1,Robo3基因的基因表达水平与启动子甲基化状态.实验数据应用Paired t检验. 结果 Slit1、Slit2、Slit3基因除个别细胞株外,在不同转移潜能细胞株中均发生了DNA甲基化,同时Slit1和Slit3在mRNA水平几乎均不表达,Slit2基因表达程度在不同转移潜能的细胞株之间存在差异,随着转移潜能的增加表达大致呈下降趋势.作为Slit2受体的Robo1基因在10株肝癌细胞株中均发生甲基化修饰,但除在SMMC-7721、BEL-7402、L02不表达外,其余7种细胞株均有表达.Robo3基因相关CpG岛在9种肝癌细胞株中均未发生甲基化,同时其在mRNA水平均无表达. 结论 Slit/Robo可能在肝癌发生和发展中发挥作用.而Robo3则在肝癌中不发生表达而且其表达沉默可能不受甲基化方式调控.     

Epigenetic silencing of WIF-1 in hepatocellular carcinomas

Purpose

To examine the expression profile and promoter methylation status of WIF-1 in hepatocellular carcinoma (HCC) and identify the possible relationship between the WIF-1 expression pattern and promoter methylation status.

Methods

Quantitative real-time PCR was performed to detect mRNA level of WIF-1 in 4 HCC cell lines, 15 paired HCC clinical samples and 3 normal liver tissues. Methylation-specific PCR and bisulfite DNA sequencing were used in methylation analysis. In vitro assays for HCC cells, colony formation and cell proliferation assay were carried out to observe the effect of WIF-1 on cell growth; TOP-flash luciferase analysis was employed to determine its role in the Wnt pathway.

Results

Quantitative real-time PCR analysis showed the extensive low expression of WIF-1 mRNA in HCC, and this down-regulation was generally dependent on the degree of methylation at its promoter region. In vitro assays indicated WIF-1 can inhibit cell growth by blocking Wnt signaling in HCC cells.

Conclusions

WIF-1 silencing as a result of its promoter hypermethylation may be a frequent event in HCC.     

Germline promoter hypermethylation of tumor suppressor genes in gastric cancer

AIM: To explore germline hypermethylation of the tumor suppressor genes MLH1, CDH1 and P16^INK4a in suspected cases of hereditary gastric cancer (GC).METHODS: A group of 140 Chinese GC patients in whom the primary cancer had developed before the age of 60 or who had a familial history of cancer were screened for germline hypermethylation of the MLH1, CDH1 and P16^INK4a tumor suppressor genes. Genomic DNA was extracted from peripheral blood leukocytes and modified by sodium bisulfite. The treated DNA was then subjected to bisulfite DNA sequencing for a specific region of the MLH1 promoter. The methylation status of CDH1 or P16^INK4a was assayed using methylation-specific PCR. Clonal bisulfite allelic sequencing in positive samples was performed to obtain a comprehensive analysis of the CpG island methylation status of these promoter regions.RESULTS: Methylation of the MLH1 gene promoter was detected in the peripheral blood DNA of only 1/140 (0.7%) of the GC patient group. However, this methylation pattern was mosaic rather than the allelic pattern which has previously been reported for MLH1 in hereditary non-polyposis colorectal cancer (HNPCC) patients. We found that 10% of the MLH1 alleles in the peripheral blood DNA of this patient were methylated, consistent with 20% of cells having one methylated allele. No germline promoter methylation of the CDH1 or P16^INK4a genes was detected.CONCLUSION: Mosaic germline epimutation of the MLH1 gene is present in suspected hereditary GC patients in China but at a very low level. Germline epimutation of the CDH1 or P16^INK4a gene is not a frequent event.     

Connexin 32 and 43 promoter methylation in Helicobacter pylori-associated gastric tumorigenesis

AIM: To explore the mechanism of abnormal Connexin (Cx) 32 and Cx43 expression in the gastric mucosa after Helicobacter pylori (H. pylori) infection.METHODS: Biopsy specimens of gastric mucosa in different gastric carcinogenesis stages with H. pylori infection, that is, non-atrophic gastritis (NAG; n = 24), chronic atrophic gastritis (CAG; n = 25), intestinal metaplasia (IM; n = 28), dysplasia (DYS; n = 24), and gastric cancer (GC; n = 30), as well as specimens of normal gastric mucosa without H. pylori infection (NGM; n = 25), were confirmed by endoscopy and pathological examination. Cx32 and Cx43 mRNA expression was detected by real-time polymerase chain reaction (PCR). Cx32 and Cx43 promoter CpG island methylation status was determined by methylation-specific PCR (MSP), bisulfite PCR sequencing (BSP) and MassArray methods.RESULTS: The relative mRNA expression levels in the gastric mucosa of patients with NGM, NAG, CAG, IM, DYS and GC were 0.146 ± 0.011, 0.133 ± 0.026, 0.107 ± 0.035, 0.039 ± 0.032, 0.037 ± 0.01 and 0.03 ± 0.011 for Cx32; and 0.667 ± 0.057, 0.644 ± 0.051, 0.624 ± 0.049, 0.555 ± 0.067, 0.536 ± 0.058 and 0.245 ± 0.121 for Cx43, respectively, which were gradually decreasing and significantly different (GC vs NGM: P < 0.001 for Cx32, P < 0.001 for Cx43). The promoter methylation levels in the gastric mucosa from NGM to GC stages by MSP were 38.8% ± 9.0%, 43.1% ± 9.4%, 56.5% ± 3.1%, 64.4% ± 9.7%, 72.5% ± 4.2% and 79.6% ± 6.8% for Cx32; and 49.0% ± 3.9%, 58.1% ± 5.0%, 66.5% ± 7.9%, 74.0% ± 8.8%, 78.3% ± 3.6% and 88.7% ± 6.2% for Cx43, respectively, which were gradually increasing and significantly different (P = 0.039, P = 0.019). The promoter methylation levels by BSP and MassArray exhibited similar trends. Cx32 and Cx43 mRNA expression was negatively correlated with promoter methylation status and gastric carcinogenesis stages (P < 0.001, P = 0.016).CONCLUSION: Cx32 and Cx43 mRNA expression decreased gradually during H. pylori infection-associated gastric carcinogenesis, and it is associated with hypermethylation of these genes’ promoter.     

Hypermethylation and Expression Silencing of PDCD4 Gene in Hepatocellular Carcinoma: A Consort Study

Programmed cell death 4 (PDCD4) is a novel tumor suppressor, which is involved in the initiation and progression of cancers. However, the role of PDCD4 in hepatocellular carcinoma (HCC) has not been reported. The aim of this study was to investigate the molecular mechanism and clinical significance of PDCD4 inactivation in HCC.The mRNA levels of PDCD4 in HCC tissues and adjacent nontumor tissues were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Bisulfite sequencing PCR was performed to determine the methylation status of PDCD4 promoter. Furthermore, the mRNA expression level and the methylated level of PDCD4 were analyzed with the clinical and pathological characteristics.qRT-PCR analysis showed that PDCD4 mRNA levels in tumor tissues were significantly decreased compared with that in adjacent nontumor tissues. The methylation rate of PDCD4 promoter was significantly higher in HCC tissues than that in adjacent nontumor tissues. PDCD4 mRNA levels and promoter methylation levels were both statistically correlated with metastasis and the degree of differentiation in HCC. In addition, the correlation between PDCD4 hypermethylation, mRNA levels, and overall survival (OS) was statistically significant.Our results indicated that PDCD4 may be a novel candidate of tumor suppressor gene in HCC, and that promoter hypermethylation is an important mechanism for its downregulation and is also a good predictor of OS for HCC.     

Methylation of CpG sites in BCL2 major breakpoint region and the increase of BCL2/JH translocation with aging

The BCL2 breakage mechanism has been shown to be highly dependent on DNA methylation at the major breakpoint region (MBR) CpG sites. We recently described an increased frequency of BCL2/ JH translocation with aging. It is known that methylation levels change with aging. The present study aimed to determine whether methylation alterations at CpG sites of BCL2 MBR were the cause of increased breakages with aging. We analyzed the methylation levels of three CpG sites on the region by pyrosequencing and studied if methylation levels and/or polymorphisms affecting CpG sites were associated with an increase of translocations. We observed that although the methylation levels of MBR CpG sites were higher in individuals with BCL2/JH translocation, in contrast to our expectations, these levels decreased with the age. Moreover, we show that polymorphisms at those CpG sites leading to absence of methylation seem to be a protective factor for the apparition of translocations.

Electronic supplementary material

The online version of this article (doi:10.1007/s11357-015-9834-5) contains supplementary material, which is available to authorized users.     

MT1M and MT1G promoter methylation as biomarkers for hepatocellular carcinoma

AIM:To investigate the potential of promoter methylation of two tumor suppressor genes(TSGs)as biomarkers for hepatocellular carcinoma(HCC).METHODS:A total of 189 subjects were included in this retrospective cohort,which contained 121 HCC patients without any history of curative treatment,37 patients with chronic hepatitis B(CHB),and 31 normal controls(NCs).DNA samples were extracted from 400μL of serum of each subject and then modified using bisulfite treatment.Methylation of the promoters of the TSGs(metallothionein1M,MT1M;and metallothionein 1G,MT1G)was determined using methylation-specific polymerase chain reaction.The diagnostic value of combined MT1M and MT1G promoter methylation was evaluated using the area under the receiver operating characteristic curves.RESULTS:Our results indicated that the methylation status of serum MT1M(48.8%,59/121)and MT1G(70.2%,85/121)promoters in the HCC group was significantly higher than that in the CHB group(MT1M 5.4%,2/37,P<0.001;MT1G 16.2%,6/37,P<0.001)and NC group(MT1M 6.5%,2/31,P<0.001;MT1G 12.9%,4/27,P<0.001).Aberrant serum MT1M promoter methylation gave higher specificity to discriminate HCC from CHB(94.6%)and NCs(93.5%),whereas combined methylation of serum MT1M and MT1G promoters showed higher diagnostic sensitivity(90.9%),suggesting that they are potential markers for noninvasive detection of HCC.Furthermore,MT1M promoter methylation was positively correlated with tumor size(rs=0.321,P<0.001),and HCC patients with both MT1M and MT1G promoter methylation tended to show a higher incidence of vascular invasion or metastasis(P=0.018).CONCLUSION:MT1M and MT1G promoter methylation may be used as serum biomarkers for noninvasive detection of HCC.     

EMs患者在位子宫内膜hMLH1蛋白表达变化及其基因启动子CpG岛甲基化观察

目的观察子宫内膜异位症（EM s）患者在位子宫内膜组织中hMLH1蛋白的表达变化及hMLH1基因启动子CpG岛甲基化情况。方法采用免疫组化法分别检测52例（Ⅰ、Ⅱ、Ⅲ、Ⅳ期分别为9、16、12、15例）EM s患者及30例健康志原者（对照组）在位子宫内膜中的hMLH1,采用甲基化特异性聚合酶链反应（MSP）法检测两组在位子宫内膜hMLH1启动子CpG岛甲基化情况。分离hMLH1启动子CpG岛甲基化异常者在位内膜中的腺细胞和间质细胞,采用MSP志愿分别检测两种细胞hMLH1启动子CpG岛甲基化情况。结果 EM s组中hMLH1蛋白表达减弱共6例,其中Ⅰ、Ⅱ、Ⅲ、Ⅳ期分别为0、0、1、5例,其余样本hMLH1蛋白表达均呈阳性;对照组30例无hMLH1蛋白表达减弱者,hMLH1蛋白表达均表现为阳性。EM s组中hMLH1启动子CpG岛部分甲基化3例,其中Ⅰ、Ⅱ、Ⅲ、Ⅳ期分别为0、0、0、3例,余均表现为非甲基化;对照组30例均表现为hMLH1启动子CpG岛非甲基化。EM s组Ⅳ期患者与Ⅰ、Ⅱ、Ⅲ期患者及对照组相比,P均〈0.05。3例hMLH1启动子CpG岛表现为部分甲基化者子宫内膜组织中hMLH1蛋白表达均减弱,其腺细胞中hMLH1启动子区表现为半甲基化,间质细胞hMLH1启动子区未见明显甲基化条带。结论 EM s患者在位子宫内膜组织中存在hMLH1表达减弱及hMLH1启动子CpG岛部分甲基化,主要集中在腺细胞,hMLH1异常与严重EM s的发病有关。