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

The gene for ornithine transcarbamylase (OTC; EC 2.1.3.3), a urea cycle enzyme, is expressed almost exclusively in the liver and small intestine. To identify DNA elements regulating transcription of the OTC gene in the liver, transient expression analysis was carried out by using hepatoma (HepG2) and nonhepatic (CHO) cell lines. The 1.3-kilobase 5'-flanking region of the rat OTC gene directed expression of the fused chloramphenicol acetyltransferase gene in HepG2 cells much more efficiently than in CHO cells. Analysis of deletion mutants of the 5'-flanking region in HepG2 cells revealed that there are at least one negative and two positive regulatory elements within the about 220-base-pair immediate 5'-flanking region. DNase I footprint analysis showed the presence of factors binding to these regulatory elements in nuclear extracts of rat liver and brain, and footprint profiles at the two positive elements exhibited liver-specific features. Transient expression analysis also revealed the existence of an enhancer region located 11 kilobases upstream of the transcription start site. The OTC enhancer was able to activate both its own and heterologous promoters in HepG2 but not in CHO cells. The enhancer was delimited to an about 230-base-pair region, and footprint analysis of this region revealed four protected areas. Footprint profiles at two of the four areas exhibited liver-specific features, and gel shift competition analysis showed that a factor(s) binding to the two liver-specific sites is related to C/EBP. These results suggest that both liver-specific promoter and enhancer elements regulate expression of the OTC gene through interaction with liver-specific factors binding to these elements.
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PMID:Promoter and 11-kilobase upstream enhancer elements responsible for hepatoma cell-specific expression of the rat ornithine transcarbamylase gene. 230 62

Mitochondrial preornithine transcarbamylase (p-OTC) and premalate dehydrogenase (p-MDH) are the only two matrix-located preproteins so far identified for which the proteolytic processing in vitro requires the formation of genuine processing intermediates, i-OTC and i-MDH, respectively. To establish the processing of other preproteins during import with respect to the two-step processing of p-OTC and p-MDH, the chelators EDTA and 1,10-phenanthroline were used to study the import and processing of rat prechaperonin 60 (p-cpn60) and p-OTC by mitochondria from four cpn60-containing organs. We found no evidence for a secondary processing step in the maturation of p-cpn60, but a clear requirement for two-step processing of p-OTC, even in three organs which do not contain ornithine transcarbamylase. The metal-ion requirement of the p-OTC processing activities in the organelle is consistent with the proposition that the mitochondrial processing protease (MPP) and mitochondrial intermediate peptidase (MIP) activities defined in vitro [Kalousek, F., Hendrick, J.P. & Rosenberg, L. E. (1988) Proc. Natl Acad. Sci. USA 85, 7536-7540] are responsible for precursor processing in vivo. The authenticity of two-step processing in vivo was, furthermore, established by demonstrating that i-OTC accumulates to high levels in Spodoptora frugiperda insect cells supplemented with MnCl2. The inability of the insect cells to process p-OTC fully is not a characteristic of cells grown in culture since cultured rat hepatoma cells process p-OTC to the fully processed m-OTC. Finally, we find that the import and processing of p-cpn60 and p-OTC is inhibited in an identical fashion by presequence-bovine-serum-albumin conjugates. The differences in proteolytic maturation between p-cpn60 and p-OTC are therefore not likely to result from different import pathways as the two precursors compete for common components of the import apparatus.
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PMID:Prechaperonin 60 and preornithine transcarbamylase share components of the import apparatus but have distinct maturation pathways in rat liver mitochondria. 809 70

The present study reports on the frequency of liver tumors observed in a gene therapy study with AAV vectors in male mice of the B6C3F1 hybrid background, which are known to have a high frequency of spontaneous liver tumors. Male mice with mutations in their Otc gene and their wild-type siblings received AAV vectors expressing either the murine Otc or the LacZ gene. Untreated control animals were included in the study. All experimental groups, including wild-type and OTC-deficient animals not treated with vector, developed liver nodules, which in some cases were due to hepatocellular carcinoma. Vector DNA was lower in tumors than in adjacent normal liver. A statistical analysis of the data did not show an association between treatment with Otc vectors and formation of tumors in OTC-deficient mice. However, mice treated with LacZ vectors showed increased risks of tumor formation and hepatocellular carcinoma relative to untreated animals or animals that had received vectors with Otc as the transgene. It appears that AAV vectors alone do not contribute to the formation of tumors in these strains of mice although the expression of LacZ alone or in combination with vector may be problematic.
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PMID:Analysis of tumors arising in male B6C3F1 mice with and without AAV vector delivery to liver. 1675 Jun 55

Hepatocyte nuclear factor 4alpha (HNF4alpha) plays critical roles during liver development and in the transcriptional regulation of many hepatic genes in adult liver. Here we have demonstrated that in human hepatoma HepG2 cells, HNF4alpha is expressed at levels as high as in human liver but its activity on target genes is very low or absent. We have discovered that the low expression of key coactivators (PGC1alpha, SRC1, SRC2, and PCAF) might account for the lack of function of HNF4alpha in HepG2 cells. Among them, PGC1alpha and SRC1 are the two most important HNF4alpha coactivators as revealed by reporter assays with an Apo-CIII promoter construct. Moreover, the expression of these two coactivators was found to be down-regulated in all human hepatomas investigated. Overexpression of SRC1 and PGC1alpha by recombinant adenoviruses led to a significant up-regulation of well characterized HNF4alpha-dependent genes (ApoCIII, ApoAV, PEPCK, AldoB, OTC, and CYP7A1) and forced HepG2 cells toward a more differentiated phenotype as demonstrated by increased ureogenic rate. The positive effect of PGC1alpha was seen to be dependent on HNF4alpha. Finally, insulin treatment of human hepatocytes and HepG2 cells caused repression of PGC1alpha and a concomitant down-regulation of ApoCIII, PEPCK, AldoB, and OTC. Altogether, our results suggest that SRC1, and notably PGC1alpha, are key coactivators for the proper function of HNF4alpha in human liver and for an integrative control of multiple hepatic genes involved in metabolism and homeostasis. The down-regulation of key HNF4alpha coactivators could be a determinant factor for the dedifferentiation of human hepatomas.
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PMID:Underexpressed coactivators PGC1alpha and SRC1 impair hepatocyte nuclear factor 4 alpha function and promote dedifferentiation in human hepatoma cells. 1689 7

A 66 year old woman who is a manifesting heterozygote for ornithine transcarbamylase deficiency (OTCD) presented with hepatocellular carcinoma (HCC). Fourteen years prior to this presentation she participated in a phase I gene therapy study which used an adenoviral vector, thought to be non-oncogenic, to deliver a normal OTC gene to hepatocytes [1]. A recent review of data collected through a national longitudinal study of individuals with urea cycle defects [2,3] suggests that early urea cycle disorders (UCDs) are associated with hepatocellular damage and liver dysfunction in many cases. This may predispose an affected individual to a substantially increased risk of developing HCC, as has been observed in certain other inborn errors of metabolism. We speculate that the underlying urea cycle defect may be the cause of HCC in this individual.
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PMID:Hepatocellular carcinoma in a research subject with ornithine transcarbamylase deficiency. 2212 77

A 66-year-old woman heterozygous for a mutation in the ornithine transcarbamylase gene (Otc) participated in a phase I gene therapy trial for OTC deficiency. She received an adenovirus (Ad) vector expressing the functional OTC gene by intraportal perfusion. Fourteen years later she developed and subsequently died of hepatocellular carcinoma. A second subject, a 45-year-old woman, enrolled in the same trial presented with colon cancer 15 years later. We sought to investigate a possible association between the development of a tumor and prior adenoviral gene transfer in these two subjects. We developed and validated a sensitive nested polymerase chain reaction assay for recovering recombinant Ad sequences from host tissues. Using this method, we could not detect any Ad vector DNA in either tumor or normal tissue from the two patients. Our results are informative in ruling out the possibility that the adenoviral vector might have contributed to the development of cancer in those two subjects.
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PMID:Vector sequences are not detected in tumor tissue from research subjects with ornithine transcarbamylase deficiency who previously received adenovirus gene transfer. 2401 Jul 2