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

Phenobarbital (PB) added to the medium of cultured rat hepatocytes alters epidermal growth factor (EGF) dependent mitogenesis in a biphasic manner; PB concentrations less than 1.5 mM are growth stimulatory but higher concentrations significantly inhibit normal hepatocyte proliferation. In contrast, the growth of putative preneoplastic cells is inhibited less by high concentrations of PB. Mechanistic studies designed to test the ability of PB to alter the early events of EGF signal transduction demonstrate that PB neither competes with EGF for binding to the EGF receptor nor alters EGF-induced receptor down-regulation. However, pretreatment with PB (greater than 1 mM) results in a transient inhibition of EGF binding to hepatocytes. The kinetics of this effect are similar to those obtained when hepatocytes are exposed to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), a skin tumor promoter and activator of Ca2+/phospholipid-dependent protein kinase C. However, several observations suggest that distinct mechanisms mediate the responses to these two tumor promoters. First, the inhibitory effects of PB and TPA on EGF binding are additive. Also down-regulation of EGF receptors in response to TPA occurs with hepatocytes, A431 epidermal carcinoma cells, HepG2 hepatoma cells, and rat liver epithelial cells, but only hepatocytes are sensitive to PB. Furthermore, translocation of protein kinase C to the membrane occurs in hepatocytes treated with TPA but not in those treated with PB. The chronic treatment of rats with PB further sensitizes hepatocytes to EGF receptor down-regulation by in vitro PB while desensitizing them to EGF receptor down-regulation by TPA. This latter effect is correlated with a decreased ability of TPA to induce translocation of protein kinase C to the membrane. PB significantly increases the intracellular concentration of TGF-beta 1 in periportal hepatocytes but not in putative preneoplastic cells. TGF-beta 1 may therefore have an important function in regulating early stages of cell cycle progression in proliferating hepatocytes.
 ...
PMID:Liver tumor promotion: effect of phenobarbital on EGF and protein kinase C signal transduction and transforming growth factor-beta 1 expression. 202 68

The human hepatoma cell line (Li-7A) possesses a high concentration of epidermal growth factor (EGF) receptors and exhibits ectoATPase activity in the presence of either MgATP or CaATP (Knowles: J. Cell. Physiol., 134:109-116, 1988). Growth for 96 hours in the presence of both EGF and cholera toxin or another cyclic AMP elevating agent induced an ectoATPase activity which was more active with CaATP and resistant to inhibition by the sulfydryl reagent, p-chloromercuriphenylsulfonate (pCMPS) (Knowles: Arch. Biochem. Biophys., 263: 264-271, 1988). In contrast, treatment of cells with butyrate, a short chain organic acid which can be derived from the analogue, dibutyryl cyclic AMP, resulted in a 4-7-fold increase of an ectoATPase which was more active with MgATP and highly sensitive to pCMPS inhibition. Maximal induction by butyrate required 48 hours and was dependent on butyrate concentration, but was independent of EGF and cyclic AMP elevating agents. Of six organic acids tested, butyrate was most effective in the induction of the ectoMg2(+)-ATPase. The increase in the ectoMg2(+)-ATPase activity could be prevented with actinomycin D and cycloheximide, indicating that both transcription and translation were necessary for induction. In addition to the induction of the ectoMg2(+)-ATPase, butyrate induced alkaline phosphatase activity, but had no effect on a third ectoenzyme 5'-nucleotidase. These data further support our proposal that two distinct ectoATPases exist in the plasma membrane of Li-7A hepatoma cells.
 ...
PMID:Butyrate induces an ectoMg2(+)-ATPase activity in Li-7A human hepatoma cells. 216 33

A mercurial-insensitive ectoATPase, which was more active with CaATP than with MgATP, was induced when human hepatoma (Li-7A) cells were cultured in the presence of epidermal growth factor (EGF) and cholera toxin. Cholera toxin could be replaced by forskolin, 8-Br-cAMP, butyryl-cAMP, and dibutyryl-cAMP. Requirement for EGF was specific, but EGF was ineffective if added more than 24 h after the addition of forskolin or cholera toxin. It was concluded that induction of the ectoCa2(+)-ATPase was a consequence of the synergistic actions of EGF and cyclic AMP. The tyrosine kinase activity of the EGF receptor was essential for the induction of ectoCa2(+)-ATPase, since enzyme induction was abolished by a tyrosine kinase inhibitor, genistein. Cycloheximide and actinomycin D were also inhibitory to enzyme induction, indicating that enhancement of enzyme activity by EGF and cAMP was not due to post-translational modification. The results of this and previous investigations established that the two ectoATPases of Li-7A cells are under different regulation.
 ...
PMID:Synergistic modulation of ectoCa2(+)-ATPase activity of hepatoma (Li-7A) cells by epidermal growth factor and cyclic AMP. 217 88

The anchorage-independent growth of Morris hepatoma 7777 (MH) cells in serum-free medium was examined. The influence of insulin, epidermal growth factor and transforming growth factor beta 1 (TGF-beta 1) on [3H]thymidine incorporation and colony formation of the investigated cells was described. Contrary to normal rat hepatocytes TGF-beta 1 plus EGF and insulin were found to stimulate MH cells proliferation in presented conditions. A simple, chemically-defined culture system suitable for research on mitogenic peptides was proposed.
 ...
PMID:Transforming growth factor-beta 1 stimulates proliferation of Morris hepatoma cells in serum-free soft agar culture system supplemented with EGF and insulin. 220 89

A radioimmunoassay for transforming growth factor alpha (TGF-alpha) using synthetic rat sarcoma transforming growth factor and its rabbit polyclonal antibody has been developed. Using radioimmunoassays, the urinary TGF-alpha and epidermal growth factor (EGF) concentrations in 31 patients with hepatocellular carcinoma (HCC), 15 probable HCC, four metastatic liver cancer, and 33 age, sex-matched healthy controls were determined. For the first time, we have shown that the average TGF-alpha concentration for HCC patients was 21.5 +/- 20.3 micrograms per g creatinine, significantly higher than that of healthy subjects, 4.9 +/- 2.8 micrograms per g creatinine (P less than 0.001). There was no statistical difference in the level of EGF between HCC patients and controls (40.9 +/- 29.3 versus 46.2 +/- 16.6 micrograms per g creatinine; P greater than 0.05). The ratio of EGF/TGF-alpha between HCC patients (3.37 +/- 4.42) and controls (15.5 +/- 13.0) was significantly different (P less than 0.001). Among patients, 65% (20 of 31) of HCC cases and 87% (13 of 15) of probable HCC cases showed a marked elevation of TGF-alpha levels. We found only 16% (five of 31) of HCC cases with increased EGF level. EGF excretion was inversely age related. Serum total protein concentration and alkaline phosphatase activity were positively correlated to EGF concentration (r = 0.522, P less than 0.01 and rt = 0.393, P less than 0.05, respectively). There was no correlation between biochemical functions of liver and TGF-alpha concentration in HCC patients. Our results also suggested that TGF-alpha may be a useful complementary tumor marker for management of patients with clinical manifestation of HCC who have low alpha-fetoprotein levels.
 ...
PMID:Elevation of transforming growth factor alpha and its relationship to the epidermal growth factor and alpha-fetoprotein levels in patients with hepatocellular carcinoma. 243 30

We isolated a cDNA clone, pAH1005, originating from the 6.8-kilobases mRNA of the rat ascites hepatoma cell line, AH60C. The sequence was highly expressed in various tumor tissues and tumor lines in rats, mice and humans. In rats, the expression of the sequence was also observed in fetal liver of 7 and 10 days of gestation, to some extent in the regenerating liver, yet was sparse in normal adult tissues. Additionally, this expression was induced when adult rat hepatocytes in primary monolayer cultures proliferated by the addition of epidermal growth factor and insulin. Southern blot analysis showed no major gene amplification and rearrangement between DNAs from hepatoma and normal liver of the same species. In addition, in vitro nuclear transcription assay revealed that a genomic clone corresponding to the pAH1005 hybridized to the nascent RNA from isolated nuclei of AH60C but not from those of normal rat liver. All these observations suggest that the expression of the conserved sequence we isolated is closely associated with cell growth and is regulated at the transcriptional level.
 ...
PMID:Isolation and characterization of a conserved sequence highly expressed in tumors and growing cells. 243 68

Increased concentrations of the fast-acting tissue-type plasminogen activator (t-PA) inhibitor attenuate the fibrinolytic activity of pharmacologically administered activators of the fibrinolytic system such as t-PA. Accordingly, it was hypothesized that augmentation of synthesis and elaboration of inhibitor from the liver, leading to increased concentrations of inhibitor in plasma, or from endothelial cells in the vicinity of thrombi undergoing lysis, leading to increased concentrations locally, may contribute to failure of pharmacologically induced thrombolysis or to early reocclusion. Because platelets are rich in transforming growth factor beta and epidermal growth factor-like activity, it was thought that release of growth factors from platelets activated in vivo could mediate increases of the inhibitor in plasma by stimulating its formation in the liver and its local release from endothelial cells in the vicinity of thrombi. If so, fibrinolysis might be rendered more effective by concomitant prevention of platelet growth factor release. Transforming growth factor beta, a major constituent of platelets, increased concentrations of the t-PA inhibitor messenger ribonucleic acid (mRNA) in human hepatoma cells in a specific and dose-dependent manner. A peak effect was seen with 5 ng/ml and a 10-fold increase in 6 hours. Release of inhibitor protein into conditioned media increased as well. Induction of the inhibitor mRNA increase was elicited by exposure as brief as 30 minutes. Cycloheximide, an inhibitor of protein synthesis, was not inhibitory. The mechanisms responsible differed from those seen with epidermal growth factor, shown previously in the laboratory to increase inhibitor mRNA. In addition, the 2 factors were synergistic. Platelet lysates elicited effects simulating those of the purified growth factors.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Potential attenuation of fibrinolysis by growth factors released from platelets and their pharmacologic implications. 249 73

Synthesis and metabolism of the epidermal growth factor (EGF) receptor are extensively regulated to modulate cellular responses to ligand. To study regulation of EGF receptor gene expression, the 5' region of the gene was isolated from a human placental genomic library. A 5' proximal 1.1-kilobase fragment (-1100 to -19 relative to the ATG translation start site) and subfragments of this were subcloned in both forward and reverse orientations into the luciferase expression vector pSVOAL delta 5' and transfected into human cell lines. Luciferase activity was stimulated by treatment of transfected HeLa cells with EGF, 12-O-tetradecanoylphorbol 13-acetate (TPA), (Bu)2 cAMP, retinoic acid, and dexamethasone. Deletion analysis indicated full retention of activity after removal of the -1100 to -485 region (-485 to -19 fragment), but a 5-fold reduction in activity on removal of the -485 to -153 region (-153 to -19 fragment). Despite a reduction in basal activity, the proximal 134-basepair fragment retained responses to all inducers. Additivity was observed in response to maximal concentrations of TPA plus retinoic acid and of TPA plus (Bu)2 cAMP; the response to a combination of four inducers exceeded that to the RSV-LTR strong promoter. Differences in stimulated responses were observed in various recipients, with hepatoma HepG2 cells lacking responses to (Bu)2 cAMP and glioblastoma T98G cells lacking responses to EGF and TPA. These results indicate that a 134-basepair DNA fragment closely adjacent to the translation start site contains elements responsible for directing basal and stimulated expression of the EGF receptor gene.
 ...
PMID:Regulation of epidermal growth factor receptor gene expression. 254 Apr 31

The culture system of hepatocellular carcinoma (HCC) has been established and the effect of hepatotrophic factors on these cell lines have been studied. During this study the effect of the human epidermal growth factor intensifying anti-tumor action of anti-tumor agents will be evaluated. HCC cell lines (C-HC-4, C-HC-20) show logarithmic growth in the serum-free medium. These growth curves after administration of 1 x 10(-12- -8) M of hEGF were measured, and the existence of the hEGF receptors was evaluated using the ABC method. The growth curve of HC-4 transplanted into nude mice was measured in 4 groups; the control group, the hEGF group, the gamma Interferon (gamma IFN) group, and the hEGF + gamma IFN group. The hEGF enhanced the cell growth of C-HC-4 and C-HC-20, and EGF receptors were confirmed immunohistologically. In the hEGF+ gamma IFN group, growth inhibition seems to be most important. The hEGF may intensify the anti-tumor action of the anti-tumor agents.
 ...
PMID:[Development of a new therapeutic method in hepatocellular carcinoma using a culture system--the intensifying effect of human epidermal growth factor (hEGF) on the antitumor action of antitumor agents]. 254 26

Data are presented from a comparative research on expression of epidermal growth factor (EGF) receptors and response to EGF of six independently established cell lines derived from human hepatoma. These lines differ in terms of the degree of differentiation, presence of hepatitis B virus (HBV) DNA copies in integrated form and expression of HBV genes. Our results indicate differential expression of membrane EGF receptors and differential response to EGF under serum- and hormone-free culture conditions. Furthermore, a significant difference in affinity could be detected between EGF receptors of the two highly dedifferentiated cell lines (HA22T/VGH and Li7A) whose replication is inhibited by EGF concentrations capable of stimulating more differentiated phenotypes.
 ...
PMID:Expression of high- and low-affinity epidermal growth factor receptors in human hepatoma cell lines. 254 52


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>