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)

Chimeric genes were constructed by fusion of various regions of the 5'-flanking sequence from the phosphoenolpyruvate carboxykinase (GTP) (PEPCK) gene to the chloramphenicol acetyltransferase-coding sequence and to simian virus 40 splice and polyadenylation sequences. These were used to demonstrate that two glucocorticoid regulatory elements (GREs) combine to confer glucocorticoid responsiveness upon the PEPCK gene in H4IIE hepatoma cells. Both elements, a distal one whose 5' boundary is located between -1264 and -1111 base pairs and a proximal one located between -468 and -420 base pairs relative to the transcription initiation site, act independently, in various positions and orientations, and upon the heterologous thymidine kinase promoter. Each element accounts for half of the maximal response of the chimeric genes. Therefore, two widely separated enhancerlike elements contribute equally to the response of the PEPCK gene to glucocorticoid hormones. Neither of the PEPCK GREs contains the TGTTCT consensus sequence associated with most other GREs.
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PMID:Location and characterization of two widely separated glucocorticoid response elements in the phosphoenolpyruvate carboxykinase gene. 342 1

In thymocytes of C3HA mice carrying the transplantable and ortoaminoazotoluene induced hepatomas at the time of their intense growth a drastic decrease in adenosine deaminase activity set in and 3-4-fold augmentation of intracellular concentration of dATP and dGTP, potential inhibitors of ribonucleoside diphosphate reductase was observed, leading to the reduction of the DNA synthesis. The latter event was evidenced by a suppressed 14C-thymidine incorporation into thymocytes DNA in vitro, decreased thymidine kinase activity, intracellular dTTP and depletion of dCTP pools. Only in the terminal period of hepatocarcinogenesis (12 months) a 4-fold increase in the corticosterone serum concentration was observed. As for the mice carrying transplantable 22a hepatoma, serum hormone levels augmented 4-fold as early as 24 h after tumor implantation and thereafter kept increased two fold. An elevated activity of terminal deoxynucleotidyl transferase in mouse thymocytes has been shown to be characteristic of the late periods of tumor growth reflecting the arrest of the immature cortical thymocyte differentiation. By the time hepatomas emerged in the course of hepatocarcinogenesis in spleen T and B lymphocytes a significant drop in the activity of adenosine deaminase (3-4-fold) and purine nucleoside phosphorylase (2-8-fold) was noted--the events directly correlated with the weakening of cell immune functions. The disorders described were accompanied by the accumulation of dGTP in spleen T lymphocytes, dATP in B lymphocytes and inhibition of DNA synthesis, predominantly in T lymphocytes. In the latter instance the pool of dCTP was found to be depleted. In spleen T and B lymphocytes of mice carrying solid 22a hepatoma when the peak of its growth was reached (day 5) the rate of DNA synthesis dropped. Later on (from day 8 to the animal death), however, in spite of the suppression of immune function and the decrease in adenosine deaminase activity a drastic stimulation of DNA synthesis in spleen T and B lymphocytes was observed. The increase in spleen T suppressor activity in the course of intense growth of the both types of hepatomas coincided in the time with the stimulation of the CTP-dependent thymidine kinase isoenzyme activity in total T lymphocyte population of the same organ.
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PMID:Some biochemical mechanisms underlying the impairment of T and B cell immunity in C3HA mice during hepatoma growth. 349 9

The initial rate of thymidine-(3)H incorporation into the acid-soluble pool by cultured Novikoff rat hepatoma cells was investigated as a function of the thymidine concentration in the medium. Below, but not above 2 microM, thymidine incorporation followed normal Michaelis-Menten kinetics at 22 degrees , 27 degrees , 32 degrees , and 37 degrees C with an apparent K(m) of 0.5 microM, and the V(max) values increased with an average Q(10) of 1.8 with an increase in temperature. The intracellular acid-soluble (3)H was associated solely with thymine nucleotides (mainly deoxythymidine triphosphate [dTTP]). Between 2 and 200 microM, on the other hand, the initial rate of thymidine incorporation increased linearly with an increase in thymidine concentration in the medium and was about the same at all four temperatures. Pretreatment of the cells with 40 or 100 microMp-chloromercuribenzoate for 15 min or heat-shock (49.5 degrees C, 5 min) markedly reduced the saturable component of uptake without affecting the unsaturable component or the phosphorylation of thymidine. The effect of p-chloromercuribenzoate was readily reversed by incubating the cells in the presence of dithiothreitol. Persantin and uridine competitively inhibited thymidine incorporation into the acid-soluble pool without inhibiting thymidine phosphorylation. At concentrations below 2 microM, thymidine incorporation into DNA also followed normal Michaelis-Menten kinetics and was inhibited in an apparently competitive manner by Persantin and uridine. The apparent K(m) and K(i) values were about the same as those for thymidine incorporation into the nucleotide pool. The over-all results indicate that uptake is the rate-limiting step in the incorporation of thymidine into the nucleotide pool as well as into DNA. The cells possess an excess of thymidine kinase, and thymidine is phosphorylated as rapidly as it enters the cells and is thereby trapped. At low concentrations, thymidine is taken up mainly by a transport reaction, whereas at concentrations above 2 microM simple diffusion becomes the principal mode of uptake. Evidence is presented that indicates that uridine and thymidine are transported by different systems. Upon inhibition of DNA synthesis, net thymidine incorporation into the acid-soluble pool ceased rapidly. Results from pulse-chase experiments indicate that a rapid turnover of dTTP to thymidine may be involved in limiting the level of thymine nucleotides in the cell.
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PMID:Thymidine transport by cultured Novikoff hepatoma cells and uptake by simple diffusion and relationship to incorporation into deoxyribonucleic acid. 434 49

cAMP stimulates the transcription of the gene for the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK) in rat liver. We have investigated the nucleotide sequences required for regulation of PEPCK gene expression by cAMP. A chimeric gene was constructed in which a 620-base pair fragment of the 5'-end of the PEPCK gene (including 547 base pairs of 5'-flanking sequence) was ligated to the herpes simplex virus thymidine kinase (TK) structural gene. The PEPCK promoter fragment was introduced either in the proper orientation for transcription of the TK gene or in the opposite orientation. These fusion genes and the parent vector, pOPF, which contains the intact TK gene, were transfected individually into TK-deficient FTO-2B rat hepatoma cells. FTO-2B cells contain an active endogenous PEPCK gene which is stimulated by cAMP. Cells were selected in HAT medium and grown either as mass cell cultures or as individual clones. Dibutyryl cyclic AMP (Bt2cAMP) plus theophylline (16 h) stimulated TK activity 1.6-6.1-fold in cell lines transfected with the PEPCK-TK fusion gene containing the PEPCK promoter fragment in the correct orientation. However, the intact TK gene was not induced by Bt2cAMP after transfection, nor was there any expression of the PEPCK-TK fusion gene in cells which contained the PEPCK promoter fragment in the wrong transcriptional orientation. Bt2cAMP also increased the levels of TK mRNA in cells transfected with the PEPCK-TK fusion gene, but not in cells transfected with the intact TK gene. The chimeric PEPCK-TK mRNA initiated at the PEPCK start site, as determined by S1 nuclease mapping. There was no relationship between the number of copies of the PEPCK-TK gene integrated in the various cell lines and either the basal level of TK activity or its inducibility of Bt2cAMP.
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PMID:Identification of a cAMP regulatory region in the gene for rat cytosolic phosphoenolpyruvate carboxykinase (GTP). Use of chimeric genes transfected into hepatoma cells. 609 Apr 58

The photosensitivity of bromodeoxyuridine (BrdU)-substituted cells is known to be markedly enhanced by the fluorochrome Hoechst 33258. Since the incorporation of BrdU into nucleic acids depends upon its prior phosphorylation via thymidine kinase (TK; EC 2.7.1.21), cells deficient in TK activity are refractory to photoinduced killing. These observations suggested that combined treatment with BrdU, Hoechst 33258, and visible light would constitute an efficient selective strategy for the recovery of TK- mutant cells. In this report we describe a single-step selection protocol which reduced the survival of TK+ cells by a factor of 10(5) without affecting the viability of TK- mutants. This procedure was used to isolate H4IIEC3 -derived rat hepatoma cells deficient in TK activity. The properties of several TK- hepatoma clones are discussed.
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PMID:Isolation of thymidine kinase-deficient rat hepatoma cells by selection with bromodeoxyuridine, Hoechst 33258, and visible light. 620 16

Activites of the enzymes DNA polymerase, thymidine kinase, thymidylate kinase, thymidylate synthase, and deoxycytidylate deaminase have been measured in rat and human normal and neoplastic liver, in human fetal liver, and in cell lines derived from human hepatomas and rat transplantable hepatomas. The activities of these enzymes were increased in rat transplantable hepatomas, relative to rat normal or host liver, to a degree corresponding to the rapid growth rate of these tumors. With the exception of thymidine kinase, which did not change, the activities of these enzymes increased in human hepatomas relative to the corresponding host liver (apparently normal liver tissue from the same patient) and to human normal liver. The increases in enzyme activity observed in human hepatomas were small in comparison with those found in the rapidly growing rat hepatomas. The activities of deoxycytidylate deaminase in both human and rat liver tissues were 2 to 3 orders of magnitude higher than those of the other enzymes assayed. Activities of the enzymes of DNA synthesis in a slow-growing cell line derived from a human hepatoma were similar to those in human hepatoma tissues. In the case of rapidly growing cell lines derived from rat and human hepatomas, enzyme activities were higher than those in the corresponding tissues.
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PMID:Activities of some enzymes of pyrimidine and DNA synthesis in a rat transplantable hepatoma and human primary hepatomas, in cell lines derived from these tissues, and in human fetal liver. 624 89

We have cloned circular unintegrated mouse mammary tumor virus (MMTV) DNA from infected rat hepatoma cells in bacteriophage lambda. Seven independent clones containing MMTV DNA of homogeneous length of 9 kb (five) or 10 kb (two) were identified. The five 9 kb clones had identical restriction maps consistent with that of 9 kb unintegrated DNA; the other two were aberrant. MMTV DNA inserts were purified, ligated and used for cotransfection of Ltk- cells together with a plasmid containing the thymidine kinase gene of herpes simplex virus. All Tk+ cell clones acquired new MMTV sequences and those transfected with the 9 kb MMTV DNA synthesized normal viral RNA and proteins. Viral gene expression was increased by the addition of dexamethasone.
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PMID:Cloned mouse mammary tumor virus DNA is biologically active in transfected mouse cells and its expression is stimulated by glucocorticoid hormones. 625 99

We have constructed a phage lambda library of liver DNA fragments from West African patient who died of liver failure due to advanced hepatocellular carcinoma. Four hepatitis B virus (HBV) DNA-carrying recombinants have been isolated, one clone (lambda IA22) being analyzed in greatest detail. It contains approximately 3.8 kb of HBV DNA without detectable deletions or rearrangements. One site of integration lies close to the nick in free viral DNA. The restriction map of the HBV sequences is close to those published for the ay subtype. Coconvection of mouse Ltk- cells with lambda IA22 and cloned thymidine kinase gene results in the expression of gene S and the excretion of hepatitis B surface antigen (HBsAg) particles into the culture supernatant.
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PMID:Organization and expression of hepatitis B sequences cloned from hepatocellular carcinoma tissue DNA. 630 20

Recombinant phage clones carrying integrated hepatitis B virus (HBV) DNA sequences have been isolated from two phage libraries made from human DNA of a hepatoma and a hepatoma-derived cell line. One clone from each library has been characterized both by restriction mapping and by electron microscopy. In one clone there is at least one complete and uninterrupted HBV genome, and in the other the HBV sequences are composed of two major subgenomic fragments inverted with respect to each other. The host-virus junctions are localized within the positions 1,700-2,600 base pairs on the physical map of the free viral genome. The pre-S/S (surface antigen gene) region is conserved between the two clones. The two clones do not have common cellular sequences nor do they contain cellular homologues to six retroviral oncogenes. For one clone, the hepatitis B surface antigen gene was found to be functional when introduced into mouse thymidine kinase-negative cells by transfection.
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PMID:Characterization of integrated hepatitis B viral DNA cloned from a human hepatoma and the hepatoma-derived cell line PLC/PRF/5. 630 89

Thymidine kinase was purified to near homogeneity by affinity chromatography from cytosol fraction of rat hepatoma 3924A. The enzyme had a Mr of 81,000 and was composed of two subunits of Mr = 44,000. Antiserum made against it neutralized the activities of thymidine kinase from both rat livers and hepatomas. Neutralization studies with the antiserum revealed that hepatic transformation resulted in 4-, 15- and 25-fold increase in the amount of cytosol thymidine kinase in hepatomas 16, 7787 and 3924A of slow, medium and fast growth rate, respectively.
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PMID:Increased concentration of thymidine kinase in rat hepatomas. 683 May 93


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