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 activity of DNA polymerases and thymidine kinase was compared in the MC-29 leukosis virus-induced transplantable hepatoma and in the livers of rats treated with cyclophosphamide (CP), cytosine-arabinoside (ara-C) and 5-fluoro-uracil (5-FU). The specific activity of DNA polymerase was twenty times greater in the MC-29 leukosis virus-induced hepatoma, while thymidine kinase was only 3-5 times greater than in liver. All three enzymes showed Michaelis-Menten kinetics in their substrate and template saturation curves. The template utilization of DNA polymerases from hepatoma and from liver was compared. Both had higher activities on a poly(dA) . poly(dT) template at pH 8.0, than on DNA at pH 7.5. After chromatography on a phosphocellulose column two polymerases were separated. The first peak eluted by 0.15 m KCl preferred DNA as template (polymerase alpha). The second eluted by 0.5 M KCl worked better on poly(dA) . poly(dT) (polymerase beta). Thymidine kinase was eluted by 0.25 m KCl. Inhibition by N-ethylmaleimide (NEM) showed the polymerase alpha to be sensitive and the polymerase beta to be resistant to the sulfhydryl blocking agent; similar to the respective enzymes of other eukaryotic cells. The specific activity of DNA polymerase decreased after CP treatment at 6 h and 72 h and after ara-C treatment at 72 h. The specific activities of thymidine kinase were not changed significantly in response to the drug administrations.
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PMID:DNA polymerase and thymidine kinase activities in MC-29 virus-induced transplantable hepatoma and the effect of cytostatic treatment of these activities. 710 49

Mouse teratocarcinoma cells (OTT6050) deficient for thymidine kinase were fused with rat hepatoma cells ( Fu5AH ) deficient for hypoxanthine phosphoribosyltransferase using inactivated Sendai virus. The hybrid cells were selected and cultured in the presence of HAT medium. A clonally established hybrid cell line ( As3 ), which in addition to its mouse genome contains several rat chromosomes, expresses rat specific enzyme variants and produces large primarily undifferentiated tumors, with some hepatoma characteristics in athymic nude mice. To reveal the in vivo developmental potential of these cells and to determine whether, under different experimental conditions, they are capable of participating in tissue differentiation, the As3 cells were injected into mouse blastocysts from the C57BL/6 strain. The experimental blastocysts were then transferred into the uteri of pseudopregnant foster mothers to allow further development. From a total of 212 blastocysts transplanted, 61 fetuses developed and were analysed for As3 contributions between the 10th and 18th day of gestation. Four fetuses at day 18 showed hybrid cell participation in their livers and a few organs of only endo-mesodermal origin, as judged from the presence of rat-specific enzyme variants. The enzymes were organ-specifically expressed (e.g., lactate dehydrogenase) or appeared newly during in situ differentiation while being absent in the original hybrid cells (e.g., glycerol-3-phosphate dehydrogenase). During short in vitro culture of the chimaeric organs, it was possible to select for the hybrid cells which reverted to an enzyme pattern simiar to but not identical with the As3 cell line and different to that observed in situ.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tissue preference and differentiation of malignant rat x mouse hybrid cells in chimaeric mouse fetuses. 718 53

The rapidly growing mouse Gaelstein hepatomas 22 and 22a and rat Zajdela hepatoma are characterized both by a high thymidine kinase activity, increased TTP pool and intense 14C-thymidine incorporation into DNA. This is indicative of an intensive thymidylate biosynthesis via a short, "salvage" pathway. The predominance of this pathway for thymidylate is also characteristic for the spleens of normal animals. On the contrast, in rat and mouse thymus, where the TTP pool was the highest of all normal tissues studied, the thymidine kinase activity and thymidine incorporation into DNA were relatively low. The growth of the three hepatomas under study induces involution of tumour carrier thymus, manifested in a decrease of the TTP pool and the rate of labelled thymidine incorporation into DNA, as well as in a 4-fold decrease of the thymidine kinase activity of rat thymus. In the spleen of mice carrying ascite 22a and solid 22 hepatomas an entirely opposite response to the tumour growth was observed, i. e. in the former case the organ weight and all indices of DNA synthesis were sharply reduced, while in the latter case they were substantially enhanced. In the spleen of Zajdela hepatoma carriers the DNA synthesis is suppressed as can be evidenced from the decrease of labelled thymidine incorporation into DNA and of TTP pool; the weight of organ and the thymidine kinase activity, however, exceed the normal level more than 2-fold.
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PMID:[Thymidine kinase activity, intracellular TTP content and DNA synthesis in transplantable hepatomas and lymphoid tissue of the host]. 721 50

Thymidine transport and phosphorylation were investigated in isolated rat hepatocytes and AS 30 D hepatoma cells. In contrast to hepatoma cells, hepatocytes exhibited a minimum of thymidine phosphorylation due to a 100-fold smaller thymidine kinase activity. In hepatocytes thymidine is transported by two transport systems: a specific concentrative "high affinity" system and an unspecific non-concentrative "low affinity" system. In hepatoma cells only the "low affinity" system could be detected. A single dose of 20 or 50 mg diethylnitrosamine/kg body weight induced in hepatocytes a remakable increas of thymidine kinase activity and a decrease of the transport by the "high affinity" system. Thymidine transport and phosphorylation by hepatocytes are considered to be sensitive markers for early recognition of toxin-induced liver regeneration.
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PMID:Thymidine transport in hepatocytes. An assay for hepatotoxicity. 738 98

Cells of the Morris hepatoma 7777 cultured in vitro have elevated levels of cytoplasmic thymidine kinase similar to those found in vivo. The cell-doubling time is slightly less than 24 hr. The addition of 5-fluorouracil to the culture medium (10 micrograms/ml) inhibits cell division, stimulates thymidine kinase production, and results in cell death which increases with time. Treated cells release significantly (p less than or equal to 0.01) more thymidine kinase into the culture medium than do untreated cells, and this effect can also be seen following a 60-min pulsed incubation of the cells with 5-fluorouracil. The total activity of thymidine kinase released is proportional to cell death and to the number of cells originally on the plate. These results suggest the possibility of monitoring tumor response to therapy in vivo by measuring serum levels of thymidine kinase.
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PMID:Effect of 5-fluorouracil on the release of thymidine kinase from hepatoma cells in vitro. 744 59

In the field of gene therapy using retroviral vectors, it appears impossible to introduce a foreign gene into all target cells. Therefore adjacent cell killing, the socalled bystander effect, caused by genetically modified cells provides therapeutic advantages for gene therapy against cancers. We retrovirally transduced the herpes simplex virus thymidine kinase (HSV-tk) gene into murine and rat hepatocellular carcinoma (HCC) cells. These HSV-tk gene-transduced HCC cells were cocultured with the corresponding parental cells in the presence of ganciclovir, at a concentration not at all cytotoxic to the parental cells. When parental HCC cells were cocultured with their HSV-tk gene-transduced counterparts at a high density at which most cells were in contact with one another, they were markedly eliminated. Conversely, when cocultured at a low density at which none of the cells were in contact, a weak but statistically significant bystander effect was observed. Addition of lysates of HSV-tk gene-transduced cells in the presence of ganciclovir did not cause and killing of parental cells. Furthermore, media conditioned by transduced cells with ganciclovir exhibited weak cytotoxic effects on parental cells. These results indicate that cell-cell contact plays a major causative role in the bystander effect and that minor contributors to this phenomenon are some cytotoxic substance released from transduced cells. Importantly, the bystander effect was induced in vivo as well as in vitro. When mixtures of transduced and untransduced HCC cells were implanted into the flank region of mice, intraperitoneal ganciclovir administration considerably inhibited tumor development, indicating the feasibility of gene therapy with HSV-tk gene and ganciclovir against HCC.
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PMID:Bystander effect caused by suicide gene expression indicates the feasibility of gene therapy for hepatocellular carcinoma. 748 96

The alpha-fetoprotein (AFP) gene is normally expressed in fetal liver and transcriptionally silent in adult tissues, but can be abnormally reactivated in hepatocellular carcinoma (HCC). We linked 7.6 kb of 5'-flanking DNA from the mouse AFP gene to the herpes simplex virus (HSV) thymidine kinase gene (tk), and a line of transgenic mice was produced that expressed TK in a pattern similar to endogenous AFP. When these AFP/tk transgenic mice were crossed to another transgenic line that develops multifocal HCC due to expression of a SV40 large T-antigen transgene under regulation of the albumin promoter/enhancer complex, a significant delay of tumor progression could be achieved by administration of ganciclovir (GCV), a cytotoxic compound that is a substrate for phosphorylation by viral, but not mammalian, TK. Control animals carrying only the tk gene were unaffected by GCV treatment. These results illustrate the feasibility of prophylactic gene therapy for ablation of cancer, utilizing a strategy in which the tk gene is regulated by a promoter expected to be active only in tumor cells.
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PMID:Delayed morbidity and mortality of albumin/SV40 T-antigen transgenic mice after insertion of an alpha-fetoprotein/herpes virus thymidine kinase transgene and treatment with ganciclovir. 751 48

The alpha-fetoprotein (AFP) gene is normally expressed in fetal liver and is transcriptionally silent in adult liver but is reactivated in hepatocellular carcinoma. It has been shown that the positive and negative transcriptionally regulatory elements of the human AFP gene, which play an important role in its developmental regulation, exist over the quite extended region (4 kb). We constructed a hybrid gene consisting of herpes simplex virus thymidine kinase (HSV-tk) gene under the control of the 0.3-kb human AFP gene promoter and inserted it into a retroviral vector. When AFP-producing hepatoma cells were infected with this recombinant retrovirus (LNAF0.3TK virus), the cells expressed HSV-tk gene and exhibited increased sensitivity to ganciclovir parallel with the ability of AFP production. On the other hand, the retroviral infection had little effect on ganciclovir-mediated cytotoxicity in AFP-nonproducing hepatoma or non-hepatoma cells. Moreover, the addition of dexamethasone increased the cytotoxicity of aciclovir to the virus-infected, AFP-producing cells through a glucocorticoid-responsive element in the AFP promoter, although aciclovir, by itself, had little cytotoxicity. These results demonstrate that the AFP promoter sequence alone can provide enough tumor-specific activity for therapeutic gene expression and induce selective growth inhibition by ganciclovir in the virus-infected, AFP-producing human hepatoma cells. In addition, it is possible that expression of the therapeutic gene is modulated by administration of dexamethasone or other agents that alter AFP promoter activity after gene transduction.
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PMID:Gene therapy for hepatoma cells using a retrovirus vector carrying herpes simplex virus thymidine kinase gene under the control of human alpha-fetoprotein gene promoter. 754 12

A retroviral vector carrying herpes simplex virus thymidine kinase gene was constructed, and transfected into the psi 2 packaging cells. The replication-defective retrovirus produced by this cell line (psi 2 tkn cells) was transduced into XC rat hepatoma cells, from which a cell line (XCtkn2) highly sensitive to ganciclovir was cloned. Ganciclovir suppressed the growth of XCtkn2 hepatoma and psi 2tkn cells. Both of these HSV-tk-carrying cells treated with ganciclovir showed potent 'bystander effect' on co-culturing with genetically unmodified XC hepatoma cells. In addition, intratumoral injection of XCtkn2 and psi 2tkn cells into the XC hepatomas transplanted in nude mice and subsequent ganciclovir administration suppressed in vivo growth of the hepatomas. Flow cytometry disclosed that the ganciclovir-treatment increased the relative number of XCtkn2 hepatoma and psi 2tkn cells at the G2 phase of the cell cycle. However, the nuclear fragmentation and internucleosomal DNA cleavage were not observed, indicating that the death of XCtkn2 hepatoma and psi 2tkn cells treated with ganciclovir was not apoptotic.
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PMID:Gene therapy of hepatoma: bystander effects and non-apoptotic cell death induced by thymidine kinase and ganciclovir. 755 97

The role of the proximal promoter and the far-upstream enhancer in the hepatocyte-specific and hormonal regulation of the carbamoyl-phosphate synthetase I (CPS) gene was investigated in transient transfection assays using primary rat hepatocytes, hepatoma cells, and fibroblasts. These experiments revealed that the activity of the promoter is comparable in all cells tested and is, therefore, not responsible for tissue-specific expression. The 5'-untranslated region of the mRNA is a major, non-tissue specific stimulator of expression in FTO-2B hepatoma cells, acting at the post-transcriptional level. A 469-base pair DNA fragment, 6 kilobase pairs upstream of the transcription start-site in the CPS gene, confers strong hormone-dependent tissue specific expression, both in combination with the CPS promoter and a minimized viral thymidine kinase promoter. Sequences similar to a cyclic AMP-responsive element and a glucocorticosteroid-responsive element were found in the isolated enhancer. Substitutional mutations in these sites strongly affected hormone-induced expression. Analysis of the interaction between the enhancer and parts of the CPS promoter revealed that, in addition to the TATA box, the GAG box, a motif similar to the GC box near the TATA motif, is instrumental in conferring the enhancer activity.
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PMID:The far-upstream enhancer of the carbamoyl-phosphate synthetase I gene is responsible for the tissue specificity and hormone inducibility of its expression. 755 19


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