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)

In the presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related chemicals, the Ah receptor nuclear translocator (Arnt) forms a heterodimeric complex with the ligand-bound Ah receptor, leading to recognition of dioxin-responsive elements within the enhancer of the CYP1A1 gene and transcription activation by an unknown mechanism. To understand the role of Arnt in transcription activation by the Ah receptor-Arnt heterodimer, we performed a deletion analysis of Arnt to locate domains that are directly involved in transcription activation. We showed that the C-terminal 34 amino acids of Arnt encode a transcription activation domain (TAD) that functions independently of other sequences in the Ah receptor complex when attached to the heterologous Gal4 DNA binding domain. Deletion of the C-terminal acidic-rich 14 amino acids completely abolishes activity. Sequences important in Arnt TAD function were independent of the glutamine-rich region which is an important structural feature in the TAD of other transcription factors. The strength of the Arnt TAD when compared with the strong TAD from the herpes simplex virus VP16 protein was cell-type specific. Both the Arnt and VP16 TAD were equally strong in COS-1 cells, but the Arnt TAD had weak activity in an Arnt-deficient mouse hepatoma cell line and was not needed for restoration of CYP1A1 activation. These results imply that for CYP1A1 activation the Ah receptor provides the dominant activation function for the heterodimer in hepatoma cells. The potential of the Arnt TAD to contribute to activation by the Ah receptor complex is likely determined by availability or activity of cell-specific factors with which the TAD interacts.
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PMID:Identification of a cell-specific transcription activation domain within the human Ah receptor nuclear translocator. 880 43

We investigated whether the glucocorticoid-mediated mechanisms controlling P-glycoprotein (pgp2 or mdr1b) are similar in normal hepatocytes compared with the H35 hepatoma cell line. In primary rat hepatocytes, dexamethasone (DEX) caused a dose- and time-dependent decrease in the amount of the pgp2 mRNA, which correlated with functional pgp2 expression (intracellular accumulation of [3H]vincristine). The suppression of pgp2 mRNA was specific for glucocorticoids because a representative estrogen and progestin were without effect, and DEX suppression of pgp2 mRNA could be reversed by cotreatment with an anti-glucocorticoid. DEX suppression of pgp2 mRNA appears to be posttranscriptional because following actinomycin D inhibition of new RNA synthesis, the pgp2 transcript disappeared at a faster rate in DEX treated versus untreated hepatocytes. Moreover, transcriptional activity of chloramphenicol acetyltransferase plasmids containing the pgp2 promoter in primary rat hepatocytes was unaffected by DEX treatment. Thus, suppression of pgp2 mRNA by glucocorticoids in primary hepatocytes is due to a decrease in pgp2 mRNA stability. In contrast, in the H35 hepatoma cell line, DEX dose dependently increased pgp protein and pgp2 mRNA, effects which parallel transcriptional activation of the pgp2 promoter. Activation of the pgp2 promoter was specific for glucocorticoids since a representative estrogen had no significant effect on transcription of the pgp2 promoter and RU486 blocked DEX activation of pgp2 transcription. Transcriptional activation of the pgp2 promoter was not due to a global up-regulation of basal transcription factors because DEX treatment did not activate either a herpes simplex virus thymidine kinase promoter or the SV40 early gene promoter. Further studies with a panel of pgp2 5' sequence deletion plasmids revealed that the minimal promoter (-66 bp) was not activated by DEX. In contrast, inclusion of sequences up to -177 bp restored DEX-dependent transcriptional activation. These are the first studies to demonstrate that glucocorticoids regulate pgp2 by different mechanisms in normal rat hepatocytes compared to the H35 hepatoma cell line.
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PMID:Divergent regulation of the class II P-glycoprotein gene in primary cultures of hepatocytes versus H35 hepatoma by glucocorticoids. 884 10

Transduction of the herpes simplex virus thymidine kinase (HSV-tk) gene into tumor cells followed by treatment with prodrugs is one of the most promising approaches for gene therapy in cancer. The choice of prodrugs is important in order to obtain maximum anticancer effects with minimum adverse reactions. We retrovirally transduced the HSV-tk gene into murine and rat hepatocellular carcinoma (HCC) cells, and investigated their sensitivity to ganciclovir and acyclovir. Retrovirally-mediated HSV-tk transduction did not affect cell proliferation, but led to both ganciclovir- and acyclovir-dependent cytotoxicity in the HCC cells. Ganciclovir exhibited much stronger cytotoxicity on HSV-tk transduced cells than acyclovir. Importantly, HSV-tk transduced cells were completely abrogated at a ganciclovir concentration which was lower than the minimum plasma level achieved in the clinical usage of ganciclovir. Furthermore, HSV-tk transduced cells induced stronger killing of neighboring untransduced cells in the presence of ganciclovir than acyclovir. Ganciclovir may be preferable to acyclovir in the HSV-tk transduction system.
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PMID:Evaluation of prodrugs ability to induce effective ablation of cells transduced with viral thymidine kinase gene. 891 61

Several classes of viruses are in use, or are being developed, as gene therapy vectors. Viruses with small genomes containing few essential genes have the advantage of requiring only simple complementation systems to allow packaging of foreign DNA, substituted for the entire viral coding sequences. Retroviruses and the dependent parvovirus AAV (adeno-associated virus) have been used in this way, and both possess an efficient integration mechanism which should allow long-term expression of transduced genes. In some situations, however, long-term persistence may be undesirable and there is a need for small, non-integrating viral vectors. Autonomous parvoviruses, such as LuIII, have potential as such vectors for short-term expression of therapeutic genes. We previously described recombinants of LuIII that transduced reporter genes, expressed using the viral constitutive promoter, P4. We have now generated several recombinants containing regulated promoters. A virus including a liver-specific enhancer directed 10- to 20-fold preferential expression of the luciferase reporter in transduced human hepatoma (HepG2) versus HeLa cells. In additional LuIII recombinants, the luciferase reporter was linked with chimeric promoters containing binding sequences for either the yeast GAL4 protein or the bacterial tetracycline repressor. Luciferase expression was strongly activated when these viruses were used to infect cells containing a cognate trans-activator (GAL4 or tTA, a tetracycline repressor fusion with VP16 of herpes simplex), introduced by transfection. The response to tTA could be abolished, or reduced in a graded manner, by exposure of the infected cells to tetracycline. Further results suggested that an increase in basal expression, apparently mediated by the viral left terminal inverted repeat, could be minimized by interposing polyadenylation signals between this sequence and the promoter. These results confirm that appropriate transcriptional regulation can be achieved for genes transduced by an autonomous parvovirus vector. Such vectors therefore show promise for the delivery of therapeutic genes in situations requiring cell-specific, short-term expression, eg in targeting suicide genes for ablation of cancer cells.
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PMID:Autonomous parvovirus transduction of a gene under control of tissue-specific or inducible promoters. 892 9

To improve the efficiency of retroviral transduction into human hepatoma cells, new liposomes were prepared using different cationic and neutral lipids. Their effect on the retroviral transduction was evaluated using PLC/PRF/5 hepatoma cells and Moloney murine leukemia virus-derived retrovirus carrying herpes simplex thymidine kinase gene. Those liposomes consisted of cationic lipids with a long spacer were highly efficient in enhancing retroviral transduction and also less cytotoxic. On the other hand, the length of hydrophobic domains of neutral lipids was not correlated with the efficiency in enhancing the retroviral transduction. These results suggest that liposomes which effectively enhance retrovirus transduction can be developed by using cationic lipids with new spacers.
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PMID:Structural characteristics of cationic liposomes with potent enhancing effect on retroviral transduction into human hepatoma cells. 894 15

Production of autologous tumor vaccines would be facilitated by the development of a rapid and efficient method for the transfer of genes into freshly isolated cells. To evaluate the potential of replication defective herpes simplex viral (HSV) amplicon vectors as gene transfer vehicles for tumor vaccine generation, a vector that expresses the human interleukin-2 (IL-2) gene (HSV-IL2) and one that expresses Escherichia coli beta-galactosidase (HSVlac) were tested in hepatoma cells of both murine and human origin. Gene transfer into murine hepatoma cells (HEPA 1-6) was both rapid and highly efficient: greater than 50% of cells expressed beta-Gal when infected at a multiplicity of infection (m.o.i.) of 1 with an exposure period of 20 min. Moreover, gene transfer was as efficient in tumor cells after irradiation with 10,000 rads as in nonirradiated tumor cells. Irradiated HEPA 1-6 cells infected with HSV-IL2 for 20 min secreted IL-2 at a rate of 1,200 +/- 160 ng/10(6) cells per day. C57B1/6J mice immunized with irradiated, HSV-IL-2-transduced tumor cells produced in this way demonstrated specific tumor immunity by in vitro splenocyte tumoricidal activity and by in vivo protection against tumor challenge. Human hepatobiliary tumor specimens harvested at the time of operation, irradiated, and infected with HSV-IL-2 also produced nanogram quantities of IL-2/10(6) cells per 24 hr. These results indicate that the HSV amplicon vector is a good candidate vehicle for gene transfer in the production of autologous tumor vaccines. By allowing rapid gene transfer to freshly harvested tumor specimens, these vectors bypass the requirement for cell culture and make feasible reinfusion of genetically modified and irradiated autologous cells within hours of tumor harvest.
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PMID:Rapid production of interleukin-2-secreting tumor cells by herpes simplex virus-mediated gene transfer: implications for autologous vaccine production. 895 12

The gene for liver-type arginase, an ornithine cycle enzyme, is induced by glucocorticoids in a delayed secondary manner. An enhancer element located around intron 7 of the rat arginase gene shows delayed glucocorticoid responsiveness, and it harbors two sites binding with members of the CCAAT/enhancer binding protein (C/EBP) family. Here, we investigate the role of these C/EBP binding sites in glucocorticoid response of the arginase gene. When inserted in front of the herpes simplex virus thymidine kinase promoter, these C/EBP sites exhibited glucocorticoid responsiveness in reporter transfection assay using rat hepatoma H4IIE cells. In footprint analysis using nuclear extracts of H4IIE cells, profiles of the protected areas of the two C/EBP sites changed when cells were treated with dexamethasone. In gel shift analysis, the complex formation for the two C/EBP sites was augmented in response to dexamethasone. Antibody supershift/inhibition analysis demonstrated that a major portion of the binding proteins induced by dexamethasone is C/EBPbeta. Induction of arginase mRNA by dexamethasone was preceded by augmentation of the C/EBP site-binding activities, which followed increase in C/EBPbeta mRNA. These results were consistent with the notion that the glucocorticoid response of the arginase gene is mediated by C/EBPbeta.
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PMID:The glucocorticoid-responsive gene cascade. Activation of the rat arginase gene through induction of C/EBPbeta. 901 25

In rats with diethylnitrosamine (DENA)-induced hepatocellular carcinoma (HCC), we studied in vivo gene transfer efficiency using intraportal injections of recombinant adenovirus carrying the lacZ reporter gene (AdCMVlacZ) and the therapeutic efficacy of adenovirus-mediated transfer of the thymidine kinase gene of the herpes simplex virus (HSV-tk) followed by ganciclovir (GCV) administration. DENA was very effective in inducing HCC but also stimulated nontumor cell replication, as shown by proliferating cell nuclear antigen (PCNA) staining. The study of in vivo gene transfer efficiency in tumor-bearing rats showed that nontumor tissue and small tumor nodules were transduced effectively whereas a poor transduction rate was noted in large tumor nodules. Concerning therapeutic efficacy, three groups of rats with established HCC were studied: group A and B received intraportally recombinant adenovirus carrying HSV-tk (AdCMVtk) or AdCMVlacZ, respectively, and 2 days after GCV was given intraperitoneally for 9 days; group C received only saline. Of the rats from groups B and C, 100% and 93% respectively, exhibited multiple HCC tumor nodules at end of the study. In contrast, a complete regression of tumor was observed in 63% of animals from group A. This group showed significant elevation of serum transaminases and a diffuse hepatotoxic lesion in liver tissue; histological signs of regeneration were observed in surviving animals. Nine out of 19 rats from group A died during the treatment period. We conclude that (i) in the DENA model of HCC, tumoral cells can be destroyed in vivo by the HSV-tk/GCV system despite poor transduction of large tumor nodules, suggesting that toxic metabolites generated by nontumor cells may exert a bystander effect on tumor tissue; (ii) significant hepatoxicity and a high mortality rate occurred in HSV-tk/GCV-treated rats; these side effects appear to be due to the fact that in DENA-treated livers enhanced cell proliferation was present not only in tumor nodules but also in nontumor parenchyma, leading to GCV sensitization of both tissues; (iii) our results have implications concerning the efficacy and potential risks of the HSV-tk/GCV system in the treatment of human HCC.
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PMID:Gene transfer and therapy with adenoviral vector in rats with diethylnitrosamine-induced hepatocellular carcinoma. 904 2

The efficacy of expression of the herpes simplex virus thymidine kinase (HSV-tk) gene under the transcriptional control of the liver-specific albumin gene promoter, followed by ganciclovir treatment, was investigated both in vitro and in vivo. Murine and rat hepatocellular carcinoma (HCC) cells infected with retroviruses carrying the HSV-tk gene under the control of the murine albumin gene promoter were selectively killed by ganciclovir treatment in vitro, whereas non-HCC cells, such as murine mammary tumor cells and fibroblast cells, which were infected with the same retroviruses, were not. Susceptibility of the retroviral-infected HCC cells to ganciclovir was more than 100-fold higher than that of the retroviral-infected non-HCC cells. When mice bearing a bulky HCC mass consisting of the retroviral-infected HCC cells were treated with systemic ganciclovir administration, complete regression of the tumors was observed without any signs of overt toxicity. Profound antitumor effects on preestablished murine HCCs were observed when wild-type HCC cells were implanted into animals with a small percentage of the retroviral-infected counterparts. When only 5% of the cells were infected with retroviruses carrying the HSV-tk gene, significant inhibition of tumor development was observed with systemic ganciclovir treatment. Importantly, animals that were treated with implantation of mixtures of the retroviral-infected and parental HCC cells, followed by ganciclovir administration, did not exhibit tumor formation and resisted subsequent rechallenge with wild-type HCC cells. Our results indicate the feasibility of combination therapy with the HSV-tk gene and ganciclovir for the treatment of HCC.
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PMID:Tissue-specific expression of HSV-tk gene can induce efficient antitumor effect and protective immunity to wild-type hepatocellular carcinoma. 913 86

Tissue- or cell-specific targeting of vectors is critical to the success of gene therapy. We describe a novel approach to virus-mediated gene therapy, where viral replication and associated cytotoxicity are limited to a specific cell type by the regulated expression of an essential immediate-early viral gene product. This is illustrated with a herpes simplex virus type 1 (HSV-1) vector (G92A) whose growth is restricted to albumin-expressing cells. G92A was constructed by inserting an albumin enhancer/promoter-ICP4 transgene into the thymidine kinase gene of mutant HSV-1 d120, deleted for both copies of the ICP4 gene. This vector also contains the Escherichia coli lacZ gene under control of the thymidine kinase promoter, a viral early promoter, to permit easy detection of infected cells containing replicating vector. In the adult, albumin is expressed uniquely in the liver and in hepatocellular carcinoma and is transcriptionally regulated. The plaquing efficiency of G92A is > 10(3) times higher on human hepatoma cells than on non-albumin-expressing human cells. The growth kinetics of G92A in albumin-expressing cells is delayed compared with that of wild-type HSV-1, likely due to aberrant expression of ICP4 protein. Cells undergoing a productive infection expressed detectable levels of ICP4 protein, as well as the reporter gene product beta-galactosidase. Confining a productive, cytotoxic viral infection to a specific cell type should be useful for tumor therapy and the ablation of specific cell types for the generation of animal models of disease.
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PMID:Transcriptional targeting of herpes simplex virus for cell-specific replication. 918 79


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