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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A substantial portion of the histone phosphorylating activity of bovine thymus chromatin can be isolated by extraction in 0.2 M NaCl. The specificity of this extract for either free histones or washed chromatin substrates was compared. The salt-extracted kinase enzymes favor H2b as the major acceptor when whole free histone is the substrate and H3 when the substrate is intact chromatin. The H3 kinase activity of bovine thymus tissue has been purified free from other detectable histone kinase activities by ammonium sulfate fractionation and is highly specific for H3 histone when assayed either with chromatin or isolated whole histone. The activity is cAMP-independent. Tryptic peptide mapping of the labeled H3 histone reveals a single site of phosphorylation. This site appears to be identical with the major site of metaphase-associated H3 phosphorylation in hepatoma tissue culture cells. No corresponding H3 phosphorylation has been detected in thymus tissue in vivo.
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PMID:An H3 histone-specific kinase isolated from bovine thymus chromatin. 20 51

Multiple protein kinase activities were isolated from nuclei of rat and hepatoma 3924A, and purified 40- to 140-fold, respectively. Hepatic protein kinase-I exhibited high activity with casein as substrate, but was relatively inactive with either liver and hepatoma chromatin or mixed histone. In contrast, hepatoma protein kinase-I showed equivalent activity with casein and liver chromatin. Protein kinase-IIA, -IIB and-IIC from both tissues were more active with liver chromatin in comparison to casein and hepatoma chromatin, and exhibited similar electrophoretic profiles of 32P-chromatin.
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PMID:Multiple nuclear protein kinase activities in rat liver and hepatoma 3924A. 21 Sep 25

The non-histone chromosomal proteins (NHCP) of a rapidly and slowly proliferating transplantable hepatocellular carcinoma (THC) were compared to those of normal and regenerating rat liver. The total quantity of NHCP is approximately threefold higher in the THCs than in either normal rat liver at 4 h and 44 h regenerating rat liver. Only those NHCP that can be extracted from chromatin by 0.35 M NaCl were further examined and it was observed that the proteins of this highly complex fraction could be further fractionated by their differential phenol-solubility. The phenol-soluble 0.35 NHCP contained protein(s) capable of stimulating the level of DNA-directed RNA synthesis in vitro. The total amount of this stimulatory activity was 5 times higher in the rapidly growing THC and 1.6 times higher in the slowly growing THC than in normal rat liver. In order to assess the contribution of cell-cycle dependent alterations on the increase in the amount of stimulatory activity in the THCs, 44 h regenerating rat livers were examined. This tissue represents a mix of cells in various stages of the cell cycle which is similar to that found in the THCs. It was found that the total quantity of NHCP in the 44 h regenerating rat liver was the same as in normal rat liver. The total amount of the stimulatory activity also was similar in both the normal and 44 h regenerating rat liver. The amount of the stimulatory activity was found to double in 4 h regenerating rat liver, however. These data suggest that the alterations observed in the NHCP of the THCs are not due solely to cell cycle dependent changes, but may represent malignancy dependent alterations.
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PMID:Comparison of transcription stimulating, phenol-soluble non-histone chromosomal proteins in normal rat liver and transplantable hepatocellular carcinomas. 21 97

The nature of nuclear proteins that are soluble in 8 M urea-50 mM phosphate, pH 7.6, was compared in rat liver and Morris hepatomas, Isoelectric focusing, using carrier ampholytes for a pH gradient of 3.5 to 10, indicated that with increasing growth rate of the hepatomas there was a progressive tendency for a decrease in nonhistone nuclear proteins with isoelectric points in the range 7.5 to 8.9 and an increase in the range 5.1 to 6.7. Studies on the influence of time on the pH gradient revealed that a nonuniform drift provided a better resolution of the pH range 7.5 to 8.9 at 7 hr than at 24 hr, while the latter time for electrofocusing gave an improved resolution of the pH range 5.1 to 6.7 Polyarcylamide gel electrophoresis in a urea-acetic acid system showed that 8 M urea-50 mM phosphate; pH 7.6 extracted a small part of the histones from nuclei of both liver and hepatomas. There was less extraction of histones from the hepatoma nuclei, especially in two rapidly growing hepatomas with the most notable difference being seen in the lysine-rich H1 histone. The results suggested that in addition to qualitative or quantitative changes in nonhistone nuclear proteins in liver cancer there are alterations in the binding of histones to chromatin.
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PMID:Nuclear protein changes in rat hepatomas correlating with growth rate. 23 25

A variety of 6- and 8-substituted analogs of cAMP (cyclic adenosine 3:5-monophosphate) have been tested for their ability to increase activity of tyrosine aminotransferase (EC 2.6.1.5) in cultured Reuber H35 hepatoma cells. Some analogs, particularly the 8-thio-substituted ones, produced effects approximately equivalent to those generated by N-6, O2'-dibutyryl cAMP. In contrast, cAMP and its O-2-monobutyryl derivative were relatively ineffective even at very high concentrations, whereas three other analogs actually depressed the activity of the aminotransferase. Changes in enzyme activity generated by the various analogs were paralleled closely by changes in the relative rate of aminotransferase synthesis. An excellent correlation was found to exist between the ability of any given analog to influence the activity of tyrosine aminotransferase and that of phosphoenolpyruvate carboxykinase (EC 4.1.1.32). A similar correlation was found to exist between the ability of various analogs to evelate the activity of these enzymes and to inhibit reversibly the growth of H35 cells. Only one of five inhibitors of cAMP phosphodiesterase activity tested produce any increase in aminotransferase activity when added alone. All of the 6- and 8-substituted analogs tested, including noniducers, stimulated f1 histone phosphorylation in crude rat liver extracts with approximately equal potencies. On the other hand, dibutyryl cAMP was only a weak activator of protein kinase in vitro, even though it is a potent enzyme inducer. A possible resolution of this apparent discrepancy has been provided by preliminary analyses of site-specific f1 histone phosphorylation in whole cells. Only compounds active as aminotransferase inducers are capable of stimulating phosphorylation of the serine-37 residue of endogenous f1 histone (3- to 10-fold).
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PMID:Effects of 6- and 8-substituted analogs of adenosine 3':5'-monophosphate on phosphoenolpyruvate carboxykinase and tyrosine aminotransferase in hepatoma cell cultures. 23 87

Injection of L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK) at a level of 10 mg/100 g body weight inhibited the incorporation of 3H-labeled amino acids into protein in Morris hepatomas 7777and 9618A2. The degree of inhibition was similar in cytoplasmic proteins and in histone and nonhistone nuclear protein fractions. There was no inhibitory effect on 3H-labeled amino acid incorporation in the livers of the tumor-bearing rats. The inhibitory effect of N-tosyl-L-lysine chloromethyl ketone (TLCK) on incorporation of 3H-labeled amino acids was observed in both the slowly growing hepatoma 7787 and the rapidly growing hepatoma 7777. In hepatoma 7777, TLCK (2.5 mg/100 g body wt) exerted a greater inhibitory effect on incorporation when administered 60 minutes before [3H]leucine injection than when injected simultaneously. Studies on tissue uptake of amino acids, thymidine, and phosphate indicated that inhibitory effects of TPCK and TLCK on active transport may be a major factor in the action of these drugs on macromolecular synthesis. The inhibitory effects of TPCK and TLCK seen in transplanted hepatomas and a colon tumor were not generally seen in normal tissues of the tumor-bearing rats.
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PMID:Selective effects of two chloromethyl ketones on amino acid and phosphate uptake in rat liver and tumors. 28 72

Hepatoma tissue culture (HTC) cell nuclei were digested with either DNase I or micrococcal nuclease and the nucleohistone digestion products fractionated by gel electrophoresis or exclusion chromatography. Under appropriate conditions, gel electrophoresis demonstrates that for both nucleases, only cleavages within the nucleosome spacer regions and not within the nucleosome core lead to freely migrating nucleohistone particles. These particles consist of nucleosome cores, nucleosomes and nucleosome oligomers. Following DNase I digestion and fractionation by exclusion chromatography, analysis of the histones indicates a direct relationship between increased spacer region susceptibility to nuclease and increased nucleosomal histone acetylation. Evidently digestion sites outside the regions of DNA protected by core histones can reflect the degree of acetylation of core histones. Such a relationship is not found when micrococcal nuclease is used to digest the samples.
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PMID:A correlation between nucleosome spacer region susceptibility to DNase I and histone acetylation. 42 5

Nuclei from hepatoma tissue culture (HTC) cells were isolated by standard methods and incubated in media commonly used for nuclease digestions (DNAase I and micrococcal nuclease) and for in vitro RNA synthesis. During the incubation, histones can be deacetylated from both control cells and cells treated with 6 mM sodium butyrate to enhance the levels of histone acetylation. Deacetylation of histone is much more apparent in nuclei isolated from sodium butyrate-treated cells. Inclusion of 6 mM sodium butyrate in the incubation medium effectively inhibits the endogenous deacetylase activity acting on histones H3 and H4, whereas sodium acetate at the same concentration has very little inhibitory effect.
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PMID:Histone deacetylation in nuclei isolated from hepatoma tissue culture cells. Inhibition by sodium butyrate. 42 71

Reuber H 35 hepatoma cells were synchronized by transfer in a serum free medium. Growth was re-initiated by addition of serum. Under these conditions DNA synthesis exhibited a maximum after 24 hours. Chromatin non-histone proteins prepared from cells at various phases of the cell cycle were incubated with [gamma-32P] ATP and the radioactive pattern of protein bound 32P was analysed by electrophoresis on polyacrylamide gels. No radioactive peak was observed in G0. Several peaks appeared 3 hours after the addition of serum. The radioactivity progressively increased until the cells reached the S phase. When most of the cells were in the S phase the radioactivity strongly decreased. Chromatin protein kinase activities were found to increase in late G1 and continued to increase in the S phase. The increase was 65% when phosvitin was the substrate, 100% with casein and histone H1. It is suggested that chromatin phosphorylated proteins could be involved in the mechanism which initiates DNA synthesis in G1 phase cells.
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PMID:Variations in some molecular events during the early phases of the Reuber H 35 cell cycle. II.-Chromatin protein phosphorylation and protein kinases. 51 30

We examined the ability of NaCl (at 0.15 to 3 M) to release non-histone proteins from chromatin of cultured rat hepatoma cells. The percentage of the non-histones released increased with increasing NaCl concentrations up to 0.75 M; 1 and 3 M NaCl were not significantly more effective. A maximum of 50% of the non-histone protein was recovered free of DNA. The release of non-histones from sheared and unsheared chromatin was similar. The electrophoretic patterns of the non-histone proteins released by NaCl resembled that of the non-histones released by sodium dodecyl sulfate, which indicates that many of the detectable components were at least partially released by NaCl. Some non-histones (especially low molecular weight polypeptides) were fully released by NaCl and other proteins were relatively resistant to NaCl release. Higher recoveries of NaCl-dissociated non-histones were obtained with sucrose gradient centrifugation than with centrifugation in the absence of sucrose.
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PMID:Analysis of the effectiveness of sodium chloride in dissociating non-histone chromatin proteins of cultured hepatoma cells. 57 60


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