UMLS:C0019204 - FACTA Search

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Query: UMLS:C0019204 (hepatocellular carcinoma)
71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

One of the "signature" phenotypes of highly malignant, poorly differentiated tumors, including hepatomas, is their remarkable propensity to utilize glucose at a much higher rate than normal cells, a property frequently dependent on the marked overexpression of type II hexokinase (HKII). As the expression of the gene for this enzyme is nearly silent in liver tissue, we tested the possibility that DNA methylation/demethylation events may be involved in its regulation. Initial studies employing methylation restriction endonuclease analysis provided evidence for differential methylation patterns for the HKII gene in normal hepatocytes and hepatoma cells, the latter represented by a highly glycolytic model cell line (AS-30D). Subsequently, sequencing following sodium bisulfite treatment revealed 18 methylated CpG sites within a CpG island (-350 to +781 bp) in the hepatocyte gene but none in that of the hepatoma. In addition, treatment of a hepatocyte cell line with the DNA methyltransferase inhibitors, 5'-azacytidine and 5'-aza-2'-deoxycytidine, activated basal expression levels of HKII mRNA and protein. Finally, stably transfecting the hepatocyte cell line with DNA demethylase also resulted in activating the basal expression levels of HKII mRNA and protein. These novel observations indicate that one of the initial events in activating the HKII gene during either transformation or tumor progression may reside at the epigenetic level.
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PMID:Glucose metabolism in cancer. Evidence that demethylation events play a role in activating type II hexokinase gene expression. 1256 45

Collagen production plays a significant role in tumor development, especially in breast cancer, hepatocarcinomas, and colorectal carcinoma. However, collagen production is decreased during oncogenic transformation of cells in culture. This study demonstrates that methylation of the collagen alpha2(I) gene transcription start site occurs frequently in human cancer cell lines (9 of 10), including breast cancer cell lines (MCF-7 and Hs578T), hepatocellular carcinoma cell lines (SNU387, SNU449, SNU398, and PLC/PRF/5), a fibrosarcoma cell line (HT1080), and colorectal carcinoma cell lines (HCT116, SW480, and SW620). In addition, the collagen gene is more methylated in colorectal cancer tissues compared with normal mucosa. The increased DNA methylation of the collagen gene in cell lines is inversely correlated with collagen mRNA steady-state levels. Most importantly, treatment of fibrosarcoma or breast carcinoma cells with a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine, resulted in lower methylation and reactivation of the collagen gene in a dose-responsive manner. This is the first demonstration that the collagen alpha2(I) gene is methylated in multiple cancer cell lines correlating with loss of collagen expression and also methylated in primary cancer tissues. These data also suggest that methylation-induced repression of collagen transcription may be a frequent occurrence in cancer.
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PMID:DNA hypermethylation near the transcription start site of collagen alpha2(I) gene occurs in both cancer cell lines and primary colorectal cancers. 1270 64

Alteration of DNA methylation is one of the most consistent epigenetic changes in human cancers. DNA methyltransferase (DNMT) 1 is a major enzyme involved in establishing genomic methylation patterns. Most of the studies concerning DNMT1 expression in human cancers have been performed only at the mRNA level. To directly examine DNMT1 protein expression levels during human hepatocarcinogenesis, 16 histologically normal liver tissues, 51 noncancerous liver tissues exhibiting chronic hepatitis or cirrhosis, which are considered to be precancerous conditions, and 53 hepatocellular carcinomas (HCCs) were subjected to immunohistochemic examination. If more than 20% of the cells exhibited nuclear DNMT1 staining, the tissue sample was considered to be DNMT1-positive. DNMT1 immunoreactivity was observed in 23 (43%) of the HCCs, but in none (0%) of the histologically normal liver or noncancerous liver tissues exhibiting chronic hepatitis or cirrhosis. The incidence of increased DNMT1 protein expression in HCCs correlated significantly with poor tumor differentiation (p = 0.0006) and portal vein involvement (p = 0.0002). Moreover, the recurrence-free (p = 0.0001) and overall (p < 0.0001) survival rates of patients with HCCs exhibiting increased DNMT1 protein expression were significantly lower than those of patients with HCCs that did not exhibit increased expression. Increased DNMT1 protein expression may play a critical role in the malignant progression of HCCs and be a biologic predictor of both HCC recurrence and a poor prognosis in HCC patients.
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PMID:Increased protein expression of DNA methyltransferase (DNMT) 1 is significantly correlated with the malignant potential and poor prognosis of human hepatocellular carcinomas. 1271 45

The related members of the interleukin 6 (IL-6) family of cytokines, IL-6, leukemia inhibitory factor (LIF), and oncostatin M, act as major inflammatory mediators and induce the hepatic acute phase reaction. Normal parenchymal liver cells express the receptors for these cytokines, and these receptors activate, to a comparable level, the intracellular signaling through signal transducer and activator of transcription (STAT) proteins and extracellular-regulated kinase (ERK). In contrast, hepatoma cell lines show attenuated responsiveness to some of these cytokines that is correlated with lower expression of the corresponding ligand-binding receptor subunits. This study tests the hypothesis that the reduced expression of LIF receptor (LIFR) observed in hepatoma cells is mediated by altered DNA methylation. H-35 rat hepatoma cells that have a greatly reduced LIF responsiveness were treated with 5-aza-2'-deoxycytidine, an inhibitor of DNA methyltransferase. Surviving and proliferating cells showed reestablished expression of LIFR protein and function. Restriction landmark genomic scanning (RLGS) demonstrated genome-wide drug-induced alterations in DNA methylation status, with striking similarities in the demethylation pattern among independently derived clonal lines. Upon extended growth in the absence of 5-aza-2'-deoxycytidine, the cells exhibit partial reversion to pretreatment patterns. Demethylation and remethylation of the CpG island within the LIFR promoter that is active in normal liver cells correlate with increased and decreased usage of this promoter in H-35 cells. In conclusion, these results indicate that transformed liver cells frequently undergo epigenetic alterations that suppress LIFR gene expression and modify the responsiveness to this IL-6 type cytokine.
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PMID:DNA methylation controls the responsiveness of hepatoma cells to leukemia inhibitory factor. 1464 63

E-cadherin is a key cell adhesion molecule implicated as a tumor suppressor, which is frequently altered in hepatocellular carcinoma, especially in hepatitis B virus (HBV)-related tumors. Here, we report that HBV X protein (HBx) represses E-cadherin expression at the transcription level. Based on the differential effects of HBx natural variants, we determined that Lys-130 in the transactivation domain of HBx is critical for the E-cadherin repression. The repression effect of HBx was abolished after treatment with DNA methyltransferase inhibitor, 5'-Aza-2'dC. In addition, methylation-specific PCR analysis revealed that the CpG island 1 of E-cadherin promoter is hypermethylated by HBx. Furthermore, HBx induces DNA methyltransferase 1 expression by stimulating its transcription. Therefore, we conclude that HBx represses E-cadherin expression by inducing methylation-mediated promoter inactivation. The reduced E-cadherin expression results in dramatic morphological changes of the HBx-expressing cells. In addition, HBx-expressing cells aggregate poorly in suspension culture, reflecting their altered intercellular interactions. The biological significance was further demonstrated by the increased collagen invasion ability of HBx-expressing cells. Therefore, the present study suggests that HBx plays a role during hepatocellular carcinogenesis by favoring cell detachment from the surrounding cells and migration outside of the primary tumor site.
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PMID:Hepatitis B virus X protein represses E-cadherin expression via activation of DNA methyltransferase 1. 1600 61

Whether DNA methyltransferase 3B (DNMT3B) is deregulated in hepatocellular carcinoma cell lines is still unclear. The expression levels of DNMT3B protein in normal liver cell line, pericacinoma cell line and hepatocellular carcinoma cell lines were compared by both Western blotting and immunocytochemistry. Long-term downregulated DNMT3B in a hepatocellular carcinoma cell line SMMC-7721 was achieved using a RNAi recombinant plasmid. The suppression of DNMT3B induced by RNA interference was confirmed using semi-quantitative RT-PCR and Western blotting. High throughput cDNA microarray was used to analyze the expression profiling of downstream genes of DNMT3B displayed in the treated cell lines and control. In the result,DNMT3B in hepatocellular carcinoma cell lines was expressed at a significantly higher level compared to those in pericacinoma cell line and normal liver cell line. A specific DNMT3B siRNA stably expressed from a plasmid vector effectively suppressed the expression of DNMT3B in SMMC-7721 cell line. By microarray analysis,26 downregulated genes and 115 upregulated genes have been identified in the DNMT3B knockdown cell line,including some important developmental genes and tumor-related genes such as SNCG, NOTCH1, MBD3, WNT11, MAOA and FACL4. The discovery showed DNMT3B was over-expressed in most hepatocellular carcinoma cell lines examined and may be linked to the carcinogenesis of hepatocytes. An array of candidate genes that are involved in the action of DNMT3B have been identified,including those related to development.
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PMID:Identification of potential genes regulated by DNA methyltransferase 3B in a hepatocellular carcinoma cell line by RNA interference and microarray analysis. 1631 77

In the present study, we investigated methylation status of the CpG islands of some major tumor suppressor genes both in human hepatocellular carcinoma and liver cancer cell lines and examined whether demethylation by arsenic trioxide (As2O3) could restore their expression in the cell lines. HepG2 and Huh-7 cells were treated with 2 to 10 micromol/L of AS2O3 and/or 1 micromol/L of 5-aza-2'-deoxycytidine for 24, 48, and 72 hours. The methylation status of the CpG island around the promoter regions of p161NK4a, RASSF1A, E cadherin, and GSTP1 was detected by a methylation-specific polymerase chain reaction (MSP). The messenger RNA (mRNA) and protein levels of these genes were determined by quantitative real-time reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemical analyses. The DNA methyltransferase (DNMT) mRNA levels and enzyme activity were also examined. The hypermethylated status of the promoter regions of p16INK4a, RASSF1A, E cadherin, and GSTP1 was observed in 10 (40%), 14 (56%), 6 (24%), and 12 (48%) of 25 patients with hepatocellular carcinoma, respectively. CpG methylation of the p16INK4a, RASSF1A, E cadherin, and GSTP1 genes was correlated to the reduction of mRNA levels in the cell lines, and mRNA expression of these 4 genes were indeed restored by low concentrations (2-6 micromol/L) of As2O3 through demethylation, as well as 1 micromol/L of 5-aza-2'-deoxycytidine. Western blot and immunohistochemical analyses confirmed that each protein was markedly enhanced after treatment with a low concentration of As2O3. In contrast, As2O3 at a high concentration (10 micromol/L) damaged cell membranes and remarkably suppressed these 4 protein levels. As2O3 decreased the mRNA expression of DNMT 1 and also dose-dependently inhibited DNMT activity. In conclusion, a low concentration of As2O3 induces CpG island demethylation of tumor suppressor genes by inhibition of DNMT and reactivates the partially/fully silenced genes in liver cancer cells.
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PMID:Arsenic trioxide inhibits DNA methyltransferase and restores methylation-silenced genes in human liver cancer cells. 1661 25

DNA methylation and histone modifications have emerged as key mechanisms in transcriptional regulation. The target of methylation-induced silencing 1 (TMS1) is a bipartite protein. Recent studies have indicated that methylation-associated silencing of TMS1 occurs in many cancers. However, whether and how TMS1 is regulated by epigenetic mechanisms in cancers remains unknown. In this study we showed that methylation of the TMS1 promoter occurred in five of six hepatocellular carcinoma (HCC) cell lines. TMS1 expression was reduced in four HCC cell lines and correlated with methylation status. Furthermore, the TMS1 promoter was completely methylated and mRNA expression was undetectable. TMS1 expression could be restored by 5-aza-2'-deoxycitidine (5-Aza-dC) (a DNA methyltransferase inhibitor) or trichostatin A (TSA) (a histone deacetylase inhibitor) alone and the promoter methylation was partially reversible. TSA was more efficient than 5-Aza-dC in inducing TMS1 expression, and the combination of 5-Aza-dC and TSA resulted in markedly synergistic reactivation of the gene and completely reversed promoter methylation. Interestingly, TMS1 promoter methylation-associated gene silencing was accompanied by histone H3 Lysine 9 (H3K9) hypoacetylation and trimethylation. 5-Aza-dC and/or TSA also had some effect on conversion of methylated to acetylated H3K9 in restoring TMS1. This conversion was dynamic at the TMS1 promoter and a decrease in H3K9 trimethylation preceded an increase in H3K9 acetylation after 5-Aza-dC and/or TSA treatment. Our results thus suggest that epigenetic inactivation of TMS1 expression is regulated by promoter hypermethylation and H3K9 modifications in a coordinated way.
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PMID:Transcriptional silencing of the TMS1/ASC tumour suppressor gene by an epigenetic mechanism in hepatocellular carcinoma cells. 1747 63

Aberrant DNA methylation on CpG islands is one of the most consistent epigenetic changes in human cancers, and the methylation process is catalyzed by DNA methyltransferase (DNMT). We evaluated i) the mRNA levels of three DNMTs; DNMT1, DNMT3a and DNMT3b, in 25 hepatocellular carcinomas (HCCs), in their corresponding non-cancerous liver tissues and in 7 normal livers by using real-time reverse transcriptase-polymerase chain reaction; ii) nuclear expression of DNMT1 and DNMT3a proteins in the HCCs by immunohistochemistry, iii) the methylation status of 5 genes; p16, p15, E-cadherin, HIC-1 and RASSF1A in the same tissues, and iv) the relationships between the above results and the clinicopathological characteristics, including prognosis. The differences in mRNA expression levels for DNMT1, DNMT3a and DNMT3b were statistically significant between HCC and normal livers (p<0.001), HCC and chronic hepatitis (p<0.001) and HCC and cirrhosis (p<0.001). An increase in mRNA expression levels of >4-fold for DNMT3b in HCCs was significantly associated with a poorer overall survival (p=0.027) and shorter metastasis-free survival (p=0.0299). A poorer recurrence-free survival was noted in HCCs with a >4-fold increase in DNMT3a mRNA (p=0.0120). The average numbers of methylated genes were 0, 1.27, 1.38 and 2.72 for normal livers, chronic hepatitis, cirrhosis and HCCs, respectively, and this progressive increase from normal livers to chronic hepatitis/cirrhosis through HCC may suggest that tumor suppressor gene methylation is an early event in hepatocarcinogenesis. These results first suggest that hepatocarcinogenesis involves an increased expression of DNMT1, DNMT3a and DNMT3b mRNA and a progressive increase in the number of methylated genes from normal liver, chronic hepatitis/cirrhosis to HCC and secondly that an increase in the DNMT3a and DNMT3b mRNA levels in HCCs relative to their non-cancerous tissues may be a predictor of poor survival.
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PMID:DNA methyltransferase expression and DNA methylation in human hepatocellular carcinoma and their clinicopathological correlation. 1754 90

Multiple regions on the chromosome arm 3p are frequently affected by loss of heterozygosity in human cancers. A candidate tumor suppressor gene is TMEM7, at 3p21.3, which encodes a transmembrane protein. TMEM7 is expressed specifically in the liver, and the encoded protein shares substantial sequence homology with human and mouse 28-kDa interferon-alpha (IFN-alpha) responsive protein. In investigation of the possible role of TMEM7 in development of hepatocellular carcinoma (HCC), we examined TMEM7 expression in 20 primary HCC and 18 HCC cell lines and found recurrent functional alterations. Although TMEM7 mRNA was expressed in normal hepatic cells, downregulation or inactivation of the gene was detected in 85% of primary HCC and 33% of HCC cell lines. To identify the mechanisms responsible, we examined genomic deletion and mutation, and also the effect of inhibitors of DNA methyltransferase and histone deacetylase on cells with low or no endogenous TMEM7 expression. Homozygous deletion of TMEM7 was not detected in 17 pairs of human HCC and corresponding noncancerous liver tissues, nor in any of the 18 HCC cell lines. TMEM7 mutation was not detected in the 18 HCC cell lines (low or normal TMEM7 expression). Treatment of two of six cell lines exhibiting downregulation or loss of TMEM7 with 5-aza-2'-deoxycytidine and trichostatin A yielded additive increase in TMEM7 expression, implicating aberrant DNA methylation and histone deacetylation in transcriptional silencing of this gene. Ectopic expression of TMEM7 in two TMEM7-deficient HCC lines suppressed cell proliferation, colony formation, and cell migration in vitro and reduced tumor formation in nude mice. Treatment of two highly invasive HCC cell lines with IFN-alpha for 7 days significantly increased TMEM7 expression and inhibited cell migration. These findings implicate loss of TMEM7 expression in hepatocarcinogenesis and suggest that modification of TMEM7 expression by IFN-alpha may have therapeutic relevance in a subset of HCC.
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PMID:The interferon-alpha responsive gene TMEM7 suppresses cell proliferation and is downregulated in human hepatocellular carcinoma. 1769 85

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