Liankun Gu

Publications (7)29.06 Total impact

• Article: The p16-Specific Reactivation and Inhibition of Cell Migration Through Demethylation of CpG Islands by Engineered Transcription Factors.

  Baozhen Zhang, Shengyan Xiang, Qiming Zhong, Yanru Yin, Liankun Gu, Dajun Deng
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  ABSTRACT: Abstract Methylation of CpG islands inactivates transcription of tumor suppressor genes including p16 (CDKN2A). Inhibitors of DNA methylation and histone deacylation are recognized as useful cancer therapeutic chemicals through reactivation of the expression of methylated genes. However, these inhibitors are not target gene-specific, so that they lead to serious side effects as regular cytotoxic chemotherapy agents. To explore the feasibility of methylated gene-specific reactivation by artificial transcription factors, we engineered a set of Sp1-like seven-finger zinc-finger proteins (7ZFPs) targeted to a 21-bp sequence of the p16 promoter and found that these 7ZFPs could bind specifically to the target p16 promoter probe. Then the p16-specific artificial transcription factors (p16ATFs) were made from these 7ZFPs and the transcription activator VP64. Results showed that transient transfection of some p16ATFs selectively up-regulated the endogenous p16 expression in the p16-active 293T cells. Moreover, the transient transfection of the representative p16ATF-6I specifically reactivated p16 expression in the p16-methylated H1299 and AGS cells pretreated with a nontoxic amount of 5'-aza-deoxycytidine (20 and 80 nM, respectively). In addition, stable transfection of the p16ATF induced demethylation of p16 CpG island and trimethylation of histone H3K4, and inhibited recruitment of DNA methyltransferase 1 and trimethylation of H3K9 and H3K27 in the p16 promoter in H1299 cells without 5'-aza-deoxycytidine pretreatment. Notably, inhibition of cell migration and invasion was observed in these p16-reactivated cells induced by transient and stable p16ATF transfection. These results demonstrate that p16ATF not only specifically reactivates p16 expression through demethylation of CpG islands, but also restores methylated p16 function.
  Human gene therapy 06/2012; 23(10):1071-81. · 4.20 Impact Factor
• Article: Characterization of human gastric carcinomarelated methylation of 9 miR CpG islands and repression of their expressions in vitro and in vivo.

  Yantao Du, Zhaojun Liu, Liankun Gu, Jing Zhou, Bu-Dong Zhu, Jiafu Ji, Dajun Deng
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  ABSTRACT: BACKGROUND: Many miR genes are located within or around CpG islands. It is unclear whether methylation of these CpG islands represses miR transcription regularly. The aims of this study are to characterize gastric carcinoma (GC)-related methylation of miR CpG islands and its relationship with miRNA expression. METHODS: Methylation status of 9 representative miR CpG islands in a panel of cell lines and human gastric samples (including 13 normal biopsies, 38 gastritis biopsies, 112 pairs of GCs and their surgical margin samples) was analyzed by bisulfite-DHPLC and sequencing. Mature miRNA levels were determined with quantitative RT-PCR. Relationships between miR methylation, transcription, GC development, and clinicopathological characteristics were statistically analyzed. RESULTS: Methylation frequency of 5 miR CpG islands (miR-9-1, miR-9-3, miR-137, miR-34b, and miR-210) gradually increased while the proportion of methylated miR-200b gradually decreased during gastric carcinogenesis (Ps < 0.01). More miR-9-1 methylation was detected in 62%-64% of the GC samples and 4% of the normal or gastritis samples (18/28 versus 2/48; Odds ratio, 41.4; P < 0.01). miR-210 methylation showed high correlation with H. pylori infection. miR-375, miR-203, and miR-193b methylation might be host adaptation to the development of GCs. Methylation of these miR CpG islands was consistently shown to significantly decrease the corresponding miRNA levels presented in human cell lines. The inverse relationship was also observed for miR-9-1, miR-9-3, miR-137, and miR-200b in gastric samples. Among 112 GC patients, miR-9-1 methylation was an independent favourable predictor of overall survival of GC patients in both univariate and multivariate analysis (P < 0.02). CONCLUSIONS: In conclusion, alteration of methylation status of 6 of 9 tested miR CpG islands was characterized in gastric carcinogenesis. miR-210 methylation correlated with H. pylori infection. miR-9-1 methylation may be a GC-specific event. Methylation of miR CpG islands may significantly down-regulate their transcription regularly.
  BMC Cancer 06/2012; 12(1):249. · 3.01 Impact Factor
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  Article: Polycomb CBX7 directly controls trimethylation of histone H3 at lysine 9 at the p16 locus.

  Qiang Li, Xiuhong Wang, Zheming Lu, Baozhen Zhang, Zhenpo Guan, Zhaojun Liu, Qiming Zhong, Liankun Gu, Jing Zhou, Budong Zhu, Jiafu Ji, Dajun Deng
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  ABSTRACT: H3K9 trimethylation (H3K9me3) and binding of PcG repressor complex-1 (PRC1) may play crucial roles in the epigenetic silencing of the p16 gene. However, the mechanism of the initiation of this trimethylation is unknown. In the present study, we found that upregulating the expression of PRC1 component Cbx7 in gastric cancer cell lines MGC803 and BGC823 led to significantly suppress the expression of genes within the p16-Arf-p15 locus. H3K9me3 formation was observed at the p16 promoter and Regulatory Domain (RD). CBX7 and SUV39H2 binding to these regions were also detectable in the CBX7-stably upregulated cells. CBX7-SUV39H2 complexes were observed within nucleus in bimolecular fluorescence complementation assay (BiFC). Mutations of the chromodomain or deletion of Pc-box abolished the CBX7-binding and H3K9me3 formation, and thus partially repressed the function of CBX7. SiRNA-knockdown of Suv39h2 blocked the repressive effect of CBX7 on p16 transcription. Moreover, we found that expression of CBX7 in gastric carcinoma tissues with p16 methylation was significantly lower than that in their corresponding normal tissues, which showed a negative correlation with transcription of p16 in gastric mucosa. These results demonstrated for the first time, to our knowledge, that CBX7 could initiate H3K9me3 formation at the p16 promoter.
  PLoS ONE 01/2010; 5(10):e13732. · 4.09 Impact Factor
• Article: Methylation of p16 CpG island associated with malignant progression of oral epithelial dysplasia: a prospective cohort study.

  Jie Cao, Jing Zhou, Yan Gao, Liankun Gu, Huanxin Meng, Hongwei Liu, Dajun Deng
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  ABSTRACT: Inactivation of p16 gene by CpG methylation is a frequent event in oral epithelial dysplasia. To investigate the predictive value of p16 methylation on malignant potential in oral epithelial dysplasia, we carried out the prospective cohort study. One hundred one patients with histologically confirmed mild or moderate oral epithelial dysplasia were included in the present cohort study. p16 Methylation status of the oral epithelial dysplasia lesions from 93 cases was obtained by methylation-specific PCR. Progression of the oral epithelial dysplasia lesions was examined in 78 cases histologically during a 45.8 months follow-up period. The association between p16 methylation and progression of oral epithelial dysplasia was analyzed. Of the 93 enrolled cases, 15 cases were lost during the follow-up because of changes of contact information, with a compliance of 83.9%. p16 Methylation was detectable in oral epithelial dysplasia lesions from 32 (41.0%) of 78 enrolled patients. Oral epithelial dysplasia-related squamous cell carcinomas were observed in 22 patients (28.2%) during the follow-up. Rate of progression to oral cancer in patients with the p16-methylated oral epithelial dysplasia was significantly higher than that with the p16-unmethylated oral epithelial dysplasia (43.8% versus 17.4%; adjusted odds ratio, 3.7; P = 0.013), especially for patients at the baseline age of > or = 60 years (adjusted odds ratio, 12.0; P = 0.003) and patients with moderate oral epithelial dysplasia (adjusted odds ratio, 15.6; P = 0.022). The overall sensitivity and specificity of prediction of malignant transformation of oral epithelial dysplasia by p16 methylation were 63.6% and 67.9%, respectively. p16 Methylation was correlated with malignant transformation of oral epithelial dysplasia and is a potential biomarker for prediction of prognosis of mild or moderate oral epithelial dysplasia.
  Clinical Cancer Research 09/2009; 15(16):5178-83. · 7.74 Impact Factor
• Article: Genetic polymorphisms of the E-cadherin promoter and risk of sporadic gastric carcinoma in Chinese populations.

  Baozhen Zhang, Kaifeng Pan, Zhaojun Liu, Jing Zhou, Liankun Gu, Jiafu Ji, Junling Ma, Wei-cheng You, Dajun Deng
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  ABSTRACT: Frequent mutations and loss of expression of E-cadherin have been reported in a number of cancers. E-cadherin germ line mutations lead to a high risk of familial diffused gastric carcinoma. In the present study, to evaluate the effect of genetic polymorphisms in the E-cadherin promoter on the risk of sporadic gastric carcinoma (SGC), a comprehensive study was conducted in two populations with high and low risk of SGC in China, respectively. Five hundred seventy-two SGC cases and 625 controls from low-risk area and 589 individuals enrolled in a long-term follow-up survey in high-risk area were studied. Polymorphisms of E-cadherin around transcription start site (-437 to +314) were analyzed by sequencing. Five variations of -347del>A, -160C>A, -73A>C, +178T>C, and +234 13N ins>del were linked tightly. The -347del/del and its strongly linked +178T/T, +234 13N ins/ins genotypes increased male SGC risk in the high-risk area significantly [odds ratio (OR), 2.22; 95% confidence intervals (95% CI), 1.10-4.46] and correlated with the severity of gastric lesions. A synergetic effect was also observed between -347del/del genotype and Helicobacter pylori infection (OR, 4.93; 95% CI, 1.65-14.71). Compared with -347del-containing haplotypes, the -347A-containing haplotype [A((-347))-C((-160))-A((-73))-C((+178))-13N del((+234))] decreased the risk of SGC among male subjects (OR, 0.61; 95% CI, 0.37-1.01). Such correlation could not be observed among subjects from the low-risk area. The present data suggest that the -347del allele of E-cadherin strongly links with the +178T and +234 13N ins alleles. The -347del/del genotype may increase the susceptibility of SGC among males in the high-risk area of China.
  Cancer Epidemiology Biomarkers &amp Prevention 09/2008; 17(9):2402-8. · 4.12 Impact Factor
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  Available from: Dajun Deng

  Article: Prevalence of A2143G mutation of H. pylori-23S rRNA in Chinese subjects with and without clarithromycin use history.

  Zhuoqi Liu, Jing Shen, Lian Zhang, Lin Shen, Qiang Li, Baozhen Zhang, Jing Zhou, Liankun Gu, Guoshuang Feng, Junling Ma, Wei-Cheng You, Dajun Deng
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  ABSTRACT: A2143G mutation of 23S rRNA gene of H. pylori results in clarithromycin (CLR) resistance. To investigate the prevalence of the CLR resistance-related A2143G mutation of the H. pylori-specific 23S rRNA gene in Chinese subjects with and without CLR use history, 307 subjects received the treatment with amoxicillin and omeprazole (OA) and 310 subjects received a placebo in 1995, and 153 subjects received a triple therapy with OA and CLR (OAC) in 2000. DNA was extracted from fasting gastric juice at the end of the intervention trial in 2003. H. pylori infection was determined by H. pylori-specific 23S rRNA PCR, ELISA, and13C-urea breath test assays. Mutations of the 23S rRNA gene were detected by RFLP assays. The presence of 23S rRNA due to H. pylori infection in the OA group remained lower than that in the placebo group 7.3 yrs after OA-therapy [51.1% (157/307) vs. 83.9% (260/310), p = 0.0000]. In the OAC group, the 23S rRNA detection rate was 26.8% (41/153) three yrs after OAC-treatment. The A2143G mutation rate among the 23S rRNA-positive subjects in the OAC group [31.7% (13/41)] was significantly higher than that in the OA group [10.2% (16/157)] and the placebo group [13.8% (36/260)]. The frequency of the AAGGG --> CTTCA (2222-2226) and AACC --> GAAG (2081-2084) sequence alterations in the OAC group was also significantly higher than those in the OA group and the placebo group. Primary prevalence of the A2143G mutation was 10~14% among Chinese population without history of CLR therapy. Administration of CLR to eliminate H. pylori infection increased the prevalence of the A2143G mutation in Chinese subjects (32%) significantly.
  BMC Microbiology 02/2008; 8:81. · 3.04 Impact Factor
• Article: p16 hypermethylation during gastric carcinogenesis of Wistar rats by N-methyl-N'-nitro-N-nitrosoguanidine.

  Hua Bai, Liankun Gu, Jing Zhou, Dajun Deng
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  ABSTRACT: Inactivation of the tumor suppressor gene, p16 by CpG hypermethylation is a common event in various tumors including gastric carcinoma. The aim of this study is to investigate if p16 hypermethylation is an early and frequent event in gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The frequency and timing of p16 hypermethylation during the multistep gastric carcinogenesis in Wistar rats were analyzed in various microdissected gastric lesions. The p16 methylation status and the presence of p16 protein were analyzed by methylation-specific PCR and immunohistochemistry, respectively. Results showed that p16 methylation frequency was correlated with the severity of gastric pathologic lesions, positively. For instance, p16 methylation was found in 2.7% of normal gastric epithelium (n = 36), 16.7% of chronic atrophy gastritis (n = 24), 37.5% of dysplasia (n = 24), 67.4% of gastric adenoma (n = 43), and 85.2% of gastric carcinoma (n = 27). The p16 methylation in the distal stomach epithelium was higher than that in the proximal stomach. p16 protein was expressed in all of 15 p16 unmethylated gastric epithelial samples, but not expressed in all of 12 p16 methylated samples. These results suggest that CpG island hypermethylation may account for the silencing of p16 in rat stomach and is an early event whose accumulation will finally lead to gastric carcinogenesis.
  Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 03/2003; 535(1):73-8. · 2.85 Impact Factor