Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0345904 (liver cancer)
 15,188 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methionine adenosyltransferase (MAT) is an essential cellular enzyme which catalyses the formation of S-adenosylmethionine, the principal methyl donor and precursor for polyamines. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT respectively. We previously described a switch in the MAT expression from MAT1A to MAT2A in human liver cancer, which offered the cancerous cell a growth advantage. Loss of MAT1A expression was due to lack of gene transcription. To study regulation of the MAT1A gene, we have cloned and characterized a 1.9 kb 5'-flanking region of the human MAT1A gene. One transcriptional start site, located 25 nt downstream from a consensus TATA box, was identified by primer extension and RNase protection assays. The promoter contains several consensus binding sites for CAAT enhancer binding protein (C/EBP) and hepatocyte-enriched nuclear factor (HNF), transcriptional factors important in liver-specific gene expression. The human MAT1A promoter was able to efficiently drive luciferase expression in Chang cells, a human liver cell line, but not in HeLa cells. Sequential deletion analysis of the promoter revealed two DNA regions upstream of the translational start site, -705 to -839 bp and -1111 to -1483 bp, which are involved in positive and negative gene regulation, respectively. Specific protein binding to these regions was confirmed by electrophoretic-mobility-shift and DNase I footprinting assays. Similar to the situation with the rat MAT1A, glucocorticoid treatment also increased human MAT1A expression and promoter activity in a dose- and time-dependent manner.
 ...
PMID:Cloning and functional characterization of the 5'-flanking region of human methionine adenosyltransferase 1A gene. 1067 69

Nine structurally different polycyclic aromatic hydrocarbons (PAHs) were tested for their ability to either agonize or antagonize the human androgen receptor (hAR) in a sensitive reporter gene assay based on CHO cells transiently cotransfected with a hAR vector and an MMTV-LUC vector. Benz[a]anthracene (B[a]A), benzo[a]pyrene (B[a]P), fluoranthene, chrysene and 7,12-dimethylbenz[a]anthracene (DMBA) were acting as antiandrogens in vitro, resulting in IC(50) values of 3.2, 3.9, 4.6, 10.3 and 10.4 microM, respectively. Only at the highest concentration tested (10 microM), a slight inhibitory effect by pyrene, phenanthrene, and anthracene was observed. In contrast, dibenzo[a,h]anthracene (DB[a,h]A) gave rise to an agonistic effect, which was added upon the effect of the androgen receptor agonist R1881 (0.1 nM). The antiandrogenic responses by PAHs (10 microM) were found to be fully reversible, determined in the presence of increasing concentrations of R1881. No cytotoxic effects of the tested compounds were observed as determined either by metabolic reduction using AlamarBlue (up to 20 microM) or determined in cells transfected with a constitutively active hAR (up to 10 microM). The well-known ability of certain PAHs to activate the Ah receptor was assessed in H4IIE liver cancer cells, stably transfected with a luciferase reporter gene system. The positive control 2,3,7,8-tetrachlorodibenzodioxin (TCDD) caused a 13-14-fold induction of luciferase activity reaching maximum activity at 0.1 nM. DB[a,h]A, B[a]P, Chrysene, B[a]A and DMBA gave rise to a 4.5-fold induction of luciferase activity at 0.03, 0.4, 0.89, 3.06, and 9.27 microM, respectively, whereas fluoranthene, pyrene, phenanthrene and anthracene were without effect. In conclusion, no clear correlation between the antiandrogenic effects and the Ah receptor activation in vitro was seen. However, the Ah receptor agonists containing four or five aromatic rings (i.e. B [a] A, B [a] P, chrysene, DMBA) appeared to be the most potent antiandrogens (with the exception of DB [a, h] A), whereas those not able to activate the Ah receptor containing three or four aromatic rings (i.e. pyrene, phenanthrene, anthracene) displayed either very weak or no antiandrogenic effect at concentrations up to 10 microM (with the exception of fluoranthene which blocked the hAR at lower concentrations, but did not activate the Ah receptor).
 ...
PMID:Environmental polycyclic aromatic hydrocarbons affect androgen receptor activation in vitro. 1077 Nov 40

The nuclear matrix (nuclear scaffold), the RNA-protein skeleton of the nucleus, has a role in the organization and function of nuclear DNA. Nuclear processes associated with the nuclear matrix include transcription, replication, repair and splicing. We have purified a nuclear matrix protein, P130, which binds to several matrix attachment regions (MARs). Since the nucleotide sequence of P130 cDNA cloned by us was closely similar to that of matrin 3 cDNA cloned, except for two incorrect nucleotides within the matrin 3 coding region, and since the functions of matrin 3 were unknown, P130, referred to as P130/Mat3, was functionally characterized. The primary structure deduced for P130/Mat3 contained two DNA binding domains with C2H2-type zinc finger motif and two RNA binding domains. In addition, there were a nuclear localization signal and several phosphorylation sites for tyrosine or serine/threonine protein kinases, suggesting its multiple functions. MAR inserted upstream from the SV40 promoter in pMAR/luc assisted luciferase gene transcription in a transient expression system in Ac2F cells. Cotransfection of a plasmid carrying P130/Mat3 cDNA downstream from the CMV promoter into Ac2F cells produced this protein a level 4 times higher than that in wild-type Ac2F, causing 20 times higher luciferase activity from pMAR/luc than that induced by pMAR/luc alone. These findings indicated that MAR functions as a cis-element to which P130/Mat3 binds as one of the possible transactivators. Nuclear matrix proteins, which are tissue- and cell-type-specific, are altered with transformation and state of differentiation. We have shown that an MAR binding protein, P230, is detectable in rat hepatoma cells but not in normal liver, and suggested that this protein is a diagnostic and prognostic marker for liver cancer. It is clear that nuclear matrix proteins hold a considerable promise as diagnostic tools for pathologists. Present evidence, including our data, suggests that nuclear matrix proteins may be useful biomarkers of neoplastic disease in the serum, body fluids, and tissues. Nuclear matrix proteins are also potential candidates for the use as tumor prognostic factors and targets of anticancer drugs through apoptosis. We will discuss screening of drugs that interact with nuclear matrix proteins and influence nuclear events.
 ...
PMID:[Functional arrangement of genomic DNA and structure of nuclear matrix]. 1086 Apr 85

Methionine adenosyltransferase (MAT), an essential enzyme that catalyzes the formation of S-adenosylmethionine (SAM), is encoded by two genes, MAT1A (liver-specific) and MAT2A (non-liver-specific). We showed a switch from MAT1A to MAT2A expression in human liver cancer, which facilitates cancer cell growth. The present work examined the role of methylation in MAT2A transcriptional regulation. We found that the human MAT2A promoter is hypomethylated in hepatocellular carcinoma, in which the gene is upregulated transcriptionally, but hypermethylated in normal liver, in which the gene is minimally expressed. Luciferase activities driven by in vitro methylated MAT2A promoter constructs were 75-95% lower than activities driven by unmethylated constructs. SAM treatment of Hep G2 cells reduced MAT2A endogenous expression by 75%, hypermethylated the MAT2A promoter, and reduced luciferase activities driven by MAT2A promoter constructs by 65-75% while not affecting MAT1A's promoter activity. Treatment of adult rat and human hepatocytes with trichostatin A, an inhibitor of histone deacetylase, upregulated MAT2A expression by more than fourfold. Collectively, these results suggest that MAT2A expression is regulated by promoter methylation and histone acetylation.
 ...
PMID:Role of promoter methylation in increased methionine adenosyltransferase 2A expression in human liver cancer. 1120 39

The clinical success of interferon-treatment has been found to vary in different individuals. To explain this, we hypothesized that responses to type 1 interferons could be partly determined by interferon regulatory factor-1 gene transcription, because the latter is an important transcription factor in the interferon system. We demonstrated that the antiproliferative effect of type 1 interferons on human liver cancer cells correlates with levels of transcription of the interferon regulatory factor-1 gene in parallel with those of p21(WAF-1) expression. Here, we investigated whether mutations in the interferon regulatory factor-1 gene cause different responses to type 1 interferons. DNA from several human liver cancer cell lines and peripheral blood mononuclear cells was investigated. Nucleotide sequences of the interferon regulatory factor-1 gene and polymerase chain reaction products of its upstream region were determined directly and after cloning. The promoter activity of the upstream region of this gene was measured by the luciferase reporter assay. We found 4 point mutations in the upstream (- 1 approximately - 495) region, and the luciferase promoter assay demonstrated that these mutations did modify promoter activity. Analysis of DNA from healthy volunteers showed that these mutations are single nucleotide polymorphisms. These results suggest that single nucleotide polymorphisms of the interferon regulatory factor-1 promoter contribute, at least in part, to determining responses to type 1 interferons. J. Cell. Biochem. Suppl. 36: 191-200, 2001.
 ...
PMID:Interferon regulatory factor 1 promoter polymorphism and response to type 1 interferon. 1145 84

Selectively replicating recombinant adenovirus has emerged as a novel strategy for the treatment of incurable human cancers. One of the major characteristics of hepatocellular carcinoma is the transcriptional reactivation of alpha-fetoprotein (AFP). In this study, we evaluated the liver cancer-specific oncolytic potential of E1B 55kDa-deleted recombinant adenovirus (YKL-1001), which retained other E1 genes driven by the AFP promoter. Transient transfection study using luciferase indicated the selective activation of the AFP promoter only in human liver cancer cells secreting AFP (HepG2, Hep3B). YKL-1001 induced both cytopathic effects exclusively in AFP-positive liver cancer cells and the growth inhibition of pre-established Hep3B xenografts. Finally, hematoxylin-eosin staining and the immunohistochemistry to the adenoviral hexon showed a large distributed necrotic area and this implied a wide spread of YKL-1001. Therefore, the present study demonstrated that YKL-1001 holds significant promise as an oncolytic agent for hepatocellular carcinoma.
 ...
PMID:Antitumoral effects of recombinant adenovirus YKL-1001, conditionally replicating in alpha-fetoprotein-producing human liver cancer cells. 1191 66

We previously reported on the isolation of a new rat ATP binding cassette (ABC) transporter, ABCB6. We now report the isolation of the full-length cDNA and genomic clones containing the human ABCB6 gene. ABCB6 is 100% identical to the cloned MTABC3 human ABC transporter and contains the typical ABC signature, Walker A and B motifs. We found that HuABCB6 is expressed at low levels in normal human liver. We found that ABCB6 was overexpressed in human hepatocellular carcinomas compared to paired surrounding non-malignant tissue. We found that there was no difference in ABCB6 gene copy between human liver cancer and its paired non-malignant tissue. Because HuABCB6 was overexpressed in human cancers compared to peri-tumoral tissue in the absence of gene amplification, transcriptional regulation may play an important role in its expression. Therefore, we isolated a 14 kb genomic DNA clone containing the HuABCB6 promoter and 5'-flanking region. The 5'-flanking region contains a CpG island, lacks an appropriately positioned TATA element and contains a number of putative transcription factor binding sites. Two transcription start sites were identified by S1 nuclease mapping at -274 and -296 bp from the start codon. Transient transfection of the HuABCB6 promoter constructs (HuABCB6/1.68, 1.39, 1.13, 0.90, 0.52) containing the luciferase reporter gene resulted in a 1100-2300-fold increase in luciferase activity compared to the empty vector control whereas HuABCB6/1.68 subcloned in the reverse orientation resulted in no activity. We observed a significant decrease in luciferase activity with the promoter constructs, HuABCB6/0.25, 0.15 and 0.06, which indicates that an orientation-dependent functional promoter is contained within our previously predicted promoter region of -315 bp to -565 bp as deletion of this 250 bp sequence resulted in a loss of promoter activity.
 ...
PMID:Isolation of a genomic clone containing the promoter region of the human ATP binding cassette (ABC) transporter, ABCB6. 1195 20

Mutational inactivation of BRCA1 confers increased risk for breast cancer. However, the underlying basis for the breast tissue-restricted, tumor-suppressive properties of BRCA1 remains poorly defined. Here, we show that BRCA1 and the estrogen receptor alpha (ER-alpha) modulated vascular endothelial growth factor (VEGF) gene transcription and secretion in breast cancer cells. ER-alpha interacted in vitro and in vivo with BRCA1, and this interaction was mediated by the AF-2 domain of ER-alpha and two domains of BRCA1, the amino-acid residues 1-306 and 428-683. Endogenous interaction of ER-alpha with BRCA1 was observed in normal MCF-10A breast epithelial cells and in breast cancer cells (MCF-7 and T47D), and this interaction was significantly reduced in the presence of estrogen. Furthermore, ER-alpha induced activation of VEGF gene transcription, using human VEGF promoter-luciferase reporter constructs. The AF-2 domain of ER-alpha was also shown to induce VEGF gene transcription activation similar to that obtained with the full-length ER-alpha. However, in the presence of BRCA1, VEGF gene transcription activation and VEGF protein secretion were significantly inhibited in a dose-dependent manner. The BRCA1 domain of 1-683 amino acid residues was required for this inhibition of VEGF gene transcription activation. Three mutated forms of BRCA1 (A1708E, M1775R and Y1853X), that have been identified in familial breast cancers, failed to associate with ER-alpha and to suppress VEGF promoter activity and VEGF protein secretion. Overexpression of wild-type BRCA1 in HCC-1937 breast cancer cells that lack endogenous functional BRCA1 significantly reduced VEGF secretion in these cells. These results demonstrate a novel pathogenic mechanism whereby mutations in BRCA1, via their interaction with ER-alpha, could promote tumorigenesis through the hormonal regulation of mammary epithelial cell proliferation and impaired VEGF function, which may lead to cancer growth and angiogenesis.
 ...
PMID:Direct interaction between BRCA1 and the estrogen receptor regulates vascular endothelial growth factor (VEGF) transcription and secretion in breast cancer cells. 1240 15

Glycine N-methyltransferase (GNMT), a multifunctional protein involved in the maintenance of the genetic stability, is often down-regulated in hepatocellular carcinoma (HCC). Using genotypic characterization of GNMT in hepatoma cell lines and in a Taiwanese population with a high incidence of liver cancer we have investigated the role of this gene in the progression of liver cancer. Six novel polymorphisms, including two short tandem repeats, one 4-nucleotide insertion/deletion polymorphism, and three single nucleotide polymorphisms, in GNMT were identified in this study. The rates of loss of heterozygosity at the GNMT locus in pairs of normal and tumor tissue from the HCC patients were approximately 36-47%. In addition, the observed heterozygosity of GNMT decreases in tumor adjacent liver DNA from HCC patients compared with that observed in blood DNA from normal individuals and HCC patients. This may result from the early event of loss of heterozygosity within the GNMT gene in the liver tissues of HCC patients. However, in this study, we did not observe the association of polymorphic GNMT alleles as inherited risk factors for HCC. We also elucidated the functional impact of genetic markers in the GNMT promoter by performing luciferase reporter gene and gel mobility shift assays. The results indicate that two polymorphisms, short tandem repeat 1 and insertion/deletion polymorphism, in the promoter region could cause allelic specific effects on the transcriptional activity of GNMT. The risk genotypes of GNMT, which presumably have a lower expression level, as estimated from in vitro functional studies, are over-represented in tumor-adjacent tissues from HCC patients. In summary, our results suggest that GNMT alteration may be an early event in HCC development and that GNMT could be a new tumor susceptibility gene for HCC.
 ...
PMID:Genotypic and phenotypic characterization of a putative tumor susceptibility gene, GNMT, in liver cancer. 1256 9

Sequence-specific small interfering RNA (siRNA) duplexes can be used for gene silencing in mammalian cells and as mechanistic probes for determining gene function. Transfection of siRNAs for the aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) mRNAs in MCF-7 breast cancer cells resulted in a 60 to 80% decrease in levels of AhR and ARNT proteins in whole-cell extracts and decreased binding of nuclear extracts to 32P-labeled dioxin-responsive element. siRNA for the AhR also decreased 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 protein, CYP1A1-dependent activity, and luciferase activity in cells transfected with an Ah-responsive construct. 17beta-estradiol (E2) induces proliferation of MCF-7 cells through enhanced G0/G1 --> S phase progression, and this response is inhibited in cells cotreated with E2 plus TCDD. The effects of TCDD on E2-induced cell-cycle progress were partially blocked in MCF-7 cells transfected with siRNA for AhR. The results also indicated that siRNA-dependent decreases in AhR protein in MCF-7 cells were accompanied by increased G0/G1 --> S phase progression, suggesting a growth-inhibitory role for the "endogenous" AhR. Surprisingly, TCDD alone induced G0/G1 --> S phase progression and exhibited estrogenic activity in MCF-7 cells transfected with siRNA for the AhR. In contrast, degradation of the AhR in HepG2 liver cancer cells resulted in decreased G0/G1 --> S phase progression, and this was accompanied by decreased expression of cyclin D1, cyclin E, cyclin-dependent kinase 2 (cdk2), and cdk4. In the absence of ligand, the AhR exhibits growth-inhibitory (MCF-7) and growth-promoting (HepG2) activity that is cell context-dependent.
 ...
PMID:Aryl hydrocarbon receptor gene silencing with small inhibitory RNA differentially modulates Ah-responsiveness in MCF-7 and HepG2 cancer cells. 1276 48


1 2 3 4 5 6 7 8 9 10 Next >>