Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Scaffold or matrix attachment regions (S/MARs) are noncoding genomic DNA sequences displaying in vitro selective binding affinity for nuclear scaffold. They have been reported to be involved in the physical attachment of genomic DNA to the nuclear scaffold, and thus in the organization of the chromatin in functional loops or domains, and in the regulation of gene expression. In this work, we report the identification of an S/MAR in a woodchuck chromosomal locus, named b3n, previously described as a recurrent site of woodchuck hepatitis virus (WHV) DNA integration in woodchuck hepatocellular carcinoma (HCC). The 4.3-kb sequence of this locus contains several Alu-like repeats and a gag-like coding region with frameshift mutations. Computer analysis revealed the presence of a region with unusually high AT content, typical of most S/MARs, and of specific motifs (A boxes, T boxes, topoisomerase II sites, and unwinding elements) overlapping or in proximity to the region with high AT content, predicting that b3n might contain an S/MAR. Fragments of the b3n locus were isolated by conventional and inverse PCR techniques. In in vitro binding experiments with both heterologous and autologous scaffold preparations, a 592-bp fragment spanning the region rich in S/MAR features showed marked scaffold affinity, which was specific when autologous scaffolds were used. The presence of an S/MAR at the b3n locus and its nature as a recurrent WHV integration site in HCC suggest the involvement of S/MAR elements in some of the mechanisms leading to liver oncogenesis.
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PMID:Identification of scaffold/matrix attachment region in recurrent site of woodchuck hepatitis virus integration. 965 45

In the woodchuck hepatitis virus (WHV)/woodchuck model for hepatitis B virus-induced hepatocellular carcinoma, frequent activation of N-myc oncogenes by WHV integration has been firmly established. N-myc2, the most frequently affected gene, was reported to be activated by WHV insertion either in the proximity of the gene or in a distant uncoding locus, win. We previously reported that a WHV integration cloned from a liver tumor was located in a chromosomal locus already described by others as the site of WHV integration in another hepatocellular carcinoma. On this basis, the locus, named b3n, was defined as a recurrent site of WHV integration. A scaffold or matrix attachment region (S/MAR) element was subsequently shown to be located in this locus approximately 1 kb from the WHV insertion sites. S/MARs are genetic elements involved both in structural and functional organization of chromosomal DNA and in stimulation of gene expression. In the present work, we investigated the possibility that an N-myc gene might be affected by integration in b3n. Analysis of a liver tumor harboring WHV integration in this locus showed N-myc2 overexpression. By restriction analysis, the b3n locus was shown to be located downstream of N-myc2, so the known sites of viral insertion in b3n were approximately 11 kb downstream of the N-myc2 promoter. Although these data support that WHV insertion in b3n activates N-myc2, the mechanisms previously described to be involved in N-myc2 activation do not appear to properly account for activation in this subset of WHV integrations. Available data suggest that activation of N-myc2 by WHV integration in b3n might be mediated by the S/MAR located near the WHV insertion.
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PMID:Activation of the N-myc2 oncogene by woodchuck hepatitis virus integration in the linked downstream b3n locus in woodchuck hepatocellular carcinoma. 1032 58

The role of viral integration in HBV induced hepatocellular carcinoma (HCC) is still controversial. In the WHV/woodchuck animal model, WHV integration was found to activate the N-myc2 oncogene either by enhancer insertion in proximity of the gene, or by integration in a distantly located uncoding locus, win. In addition, we have reported that N-myc2 activation also results from WHV integration in the b3n locus, located several kilobases downstream of N-myc2. In this work we report the search for function(s) of the b3n locus that might be possibly affected by WHV integration and indirectly activate N-myc2. A 0.5 kb region of the sequence of this locus exhibited unusual features, typical of scaffold/matrix attachment regions (S/MAR). Standard in vitro binding assays are commonly used to assess if a DNA fragment is a S/MAR. DNA fragments cloned from the b3n locus were tested for in vitro binding affinity for both heterologous and autologous nuclear scaffold preparations. Only the fragment spanning the region rich of S/MAR motifs was found to bind specifically nuclear scaffolds, thus demonstrating that a S/MAR element is present in the b3n locus. Based on these findings, we speculate that WHV integration might deregulate the S/MAR element and indirectly affect the expression of the N-myc2 gene located upstream of the S/MAR. Our findings also suggest that the role of HBV integration should be reconsidered, because a similar mechanism has not been investigated to date in human HCC.
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PMID:Scaffold attachment region located in a locus targeted by hepadnavirus integration in hepatocellular carcinomas. 1278 23

Woodchuck hepatitis virus (WHV) and the woodchuck (Marmota monax) are models for hepatocellular carcinoma (HCC) induced by hepatitis B virus (HBV). In woodchuck liver tumors, the N-myc2 proto-oncogene is frequently activated by WHV integration either close to the gene or in the b3n and win downstream loci, located 10 and 150 kb from N-myc2, respectively. A scaffold/matrix attachment region (S/MAR) regulative element was shown to be in b3n, possibly mediating activation of the upstream N-myc2 gene upon WHV integration. To investigate if S/MAR elements are in win too, a 17-kb DNA fragment corresponding to the major region of WHV insertion in this locus was cloned and sequenced. Overlapping subcloned fragments spanning candidate S/MARs predicted by sequence analysis were tested by standard in vitro binding assays. Results showed the presence of two S/MAR elements in win. The distribution of previously described WHV insertions relative to the S/MARs reinforces the hypothesis that S/MARs nearby distal WHV insertions might be involved in long-range activation of N-myc2.
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PMID:The win locus involved in activation of the distal N-myc2 gene upon WHV integration in woodchuck liver tumors harbors S/MAR elements. 1547 69

The development of genetically marked animal tumour xenografts is an area of ongoing research to enable easier and more reliable testing of cancer therapies. Genetically marked tumour models have a number of advantages over conventional tumour models, including the easy longitudinal monitoring of therapies and the reduced number of animals needed for trials. Several different methods have been used in previous studies to mark tumours genetically, however all have limitations, such as genotoxicity and other artifacts related to the usage of integrating viral vectors. Recently, we have generated an episomally maintained plasmid DNA (pDNA) expression system based on Scaffold/Matrix Attachment Region (S/MAR), which permits long-term luciferase transgene expression in the mouse liver. Here we describe a further usage of this pDNA vector with the human Ubiquitin C promoter to create stably transfected human hepatoma (Huh7) and human Pancreatic Carcinoma (MIA-PaCa2) cell lines, which were delivered into "immune deficient" mice and monitored longitudinally over time using a bioluminometer. Both cell lines revealed sustained episomal long-term luciferase expression and formation of a tumour showing the pathological characteristics of hepatocellular carcinoma (HCC) and pancreatic carcinoma (PaCa), respectively. This is the first demonstration that a pDNA vector can confer sustained episomal luciferase transgene expression in various mouse tumour models and can thus be readily utilised to follow tumour formation without interfering with the cellular genome.
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PMID:Genetic modification of cancer cells using non-viral, episomal S/MAR vectors for in vivo tumour modelling. 2311 Jan 32