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)

The mechanism by which growth hormone-binding protein (GH-BP) is generated in humans remains unclear. To address this question, we analysed human GH-receptor/GH-BP gene expression in a human hepatoma cell line (HuH7). Northern hybridisation showed that HuH7 cells contain a single mRNA species hybridising with a probe for the sequences encoding the extracellular domain of the hGH-receptor/GH-BP. These data were confirmed by solution hybridisation methods. Thereafter, the cells were treated with r-hGH at physiological (12.5, 25, 50 ng/ml) and supra-physiological (150, 500 ng/ml) concentrations over the period of 48 h. At intervals, RNase protection assays were performed to determine GH-receptor/GH-BP mRNA levels, nuclear run-on assays were carried out to determine whether changes in mRNA levels represented changes in transcription rate, and a radio-ligand binding assay was performed to measure levels of GH-BP in the medium. We found that the r-hGH-regulated changes in GH-receptor/GH-BP mRNA levels detected with the probe for sequences encoding the extracellular domain of human GH-receptor/GH-BP were identical to those previously detected using a probe for the sequences encoding the transmembrane/intracellular domain of the human GH-receptor. In addition, we found that r-hGH had a rapid effect on the levels of GH-BP in the culture medium, which differed from its effect on the GH-receptor/GH-BP mRNA levels. Furthermore, lowering of temperature resulted in a decrease of GH-BP released into the medium implying that enzymes may be involved in the releasing mechanism. These data support the idea that GH-receptor and GH-BP are encoded by a single mRNA species in humans. In addition, they suggest that GH-BP levels are not an accurate reflection of GH-receptor/GH-BP mRNA levels, but that GH-BP production is subject to r-hGH-dependent post-transcriptional regulation, perhaps at the level of post-translational cleavage of the full-length GH-receptor protein. The notion that GH-BP measurements might represent GH-receptor status at the functional level must therefore be taken with caution.
 ...
PMID:Regulation of human growth hormone-binding protein production by human growth hormone in a hepatoma cell line. 755 80

Detoxication (phase 2) enzymes, such as glutathione S-transferases (GSTs), NAD(P)H:(quinone-acceptor) oxidoreductase (QR), and UDP-glucuronsyltransferase, are induced in animal cells exposed to a variety of electrophilic compounds and phenolic antioxidants. Induction protects against the toxic and neoplastic effects of carcinogens and is mediated by activation of upstream electrophile-responsive/antioxidant-responsive elements (EpRE/ARE). The mechanism of activation of these enhancers was analyzed by transient gene expression of growth hormone reporter constructs containing a 41-bp region derived from the mouse GST Ya gene 5'-upstream region that contains the EpRE/ARE element and of constructs in which this element was replaced with either one or two consensus phorbol 12-tetradecanoate 13-acetate (TPA)-responsive elements (TREs). When these three constructs were compared in Hep G2 (human) and Hepa 1c1c7 (murine) hepatoma cells, the wild-type sequence was highly activated by diverse inducers, including tert-butylhydroquinone, Michael reaction acceptors, 1,2-dithiole-3-thione, sulforaphane,2,3-dimercapto-1-propanol, HgCl2, sodium arsenite, and phenylarsine oxide. In contrast, constructs with consensus TRE sites were not induced significantly. TPA in combination with these compounds led to additive or synergistic inductions of the EpRE/ARE construct, but induction of the TRE construct was similar to that induced by TPA alone. Transfection of the EpRE/ARE reporter construct into F9 cells, which lack endogenous TRE-binding proteins, produced large inductions by the same compounds, which also induced QR activity in these cells. We conclude that activation of the EpRE/ARE by electrophile and antioxidant inducers is mediated by EpRE/ARE-specific proteins.
 ...
PMID:Electrophile and antioxidant regulation of enzymes that detoxify carcinogens. 756 53

The gene regulatory functions of the human IL-2 receptor (IL-2R) were reconstituted in transiently transfected hepatoma cells. The combination of IL-2R beta and -gamma mediated a strong stimulation via the cytokine response element of the alpha 1-acid glycoprotein gene and the hematopoietin receptor response element, but none via the IL-6 response element or the sis-inducible element. IL-2R alpha enhanced 10-fold the sensitivity of the IL-2R beta.gamma complex to respond to IL-2 or IL-15, but did not modify the specificity or the magnitude of maximal gene regulation. A homodimerizing chimeric receptor G-CSFR-IL-2R beta could mimic the IL-2R action. The IL-2R-mediated gene regulation was similar to that seen with receptors for IL-4 and IL-7, but differed from that for IL-6 type cytokines, thrombopoietin, erythropoietin, and growth hormone. The activation of STAT proteins by the IL-2R was assessed in transfected L-cells and COS-1 cells. Although IL-2R subunits were highly expressed in these cells, no STAT protein activation was detectable. Transient overexpression of JAK3 was unable to change the signaling specificity of the hematopoietin receptors in rat hepatoma, L-, and COS cells, but established a prominent activation of the IL-6 response elements by the IL-2R and IL-4R in HepG2 cells. The data support the model that the IL-2R and related hematopoietin receptors produce at least two separate signals which control gene expression.
 ...
PMID:The action of interleukin-2 receptor subunits defines a new type of signaling mechanism for hematopoietin receptors in hepatic cells and fibroblasts. 771 38

Ferritin synthesis is regulated at the translational level by iron, but it is likely that transcriptional regulation of H and L genes is responsible for tissue-specific distribution of H and L mRNAs. In order to define the regions important for transcriptional regulation of the mouse ferritin H gene, we have linked the promoter, including the transcription start site, and 5 kilobases of upstream sequence to a reporter gene (human growth hormone). This construct and a series of 5' deletion mutants have been used to transfect erythroid (K562, mouse erythroleukemia (MEL)) and hepatoma (HepG2) cell lines. Measurement of growth hormone in the culture medium and analysis of ferritin-growth hormone transcripts by a ribonuclease protection assay revealed that a 140-base pair minimal promoter is sufficient to confer a high level of expression to the reporter gene in both cell types. In addition, a 180-base pair fragment, lying 4.5 kilobases upstream of the ferritin transcription start site, functions like an inducible enhancer during N,N'-hexamethylene-bis-acetamide-induced differentiation of MEL cells. A perfect match to a consensus binding motif to the erythroid transcription factor NF-E2 is present in this regulatory element, but the mutant NF-E2 enhancer retains the inducible activity in stably transfected MEL cells, and the results from gel retardation assays suggest that protein-DNA complexes that form in vitro between the ferritin enhancer and MEL nuclear extracts do not contain NF-E2. Thus, nuclear factors that mediate inducibility of the ferritin enhancer remain to be identified.
 ...
PMID:Mouse ferritin H subunit gene. Functional analysis of the promoter and identification of an upstream regulatory element active in erythroid cells. 805 Nov 21

Calcipotriol (MC903) is a side chain analog of the vitamin D hormone calcitriol, containing a 22-23 double bond, a 24(S)-hydroxyl function, and carbons 25, 26, and 27 incorporated into a cyclopropane ring which has been developed for treating psoriasis. The in vitro metabolism of calcipotriol was studied in two keratinocyte cell models, HPK1A and HPK1A-ras. Calcipotriol was initially converted into the 24-ketone (MC1046) and its 22,23-hydrogenated derivative (MC1080), metabolites observed in osteosarcoma, kidney, and hepatoma cell lines. We also observed the formation of further metabolites, identified as the two 23-hydroxylated derivatives of MC1080 (MC1439 and MC1441), the two 23,24-dihydroxylated compounds (MC1575 and 1577), and the side chain-cleaved compounds, tetranor-1,23-(OH)2D3 and calcitroic acid, the end products of catabolism of calcitriol. These findings suggest that calcitriol and calcipotriol may share catabolic enzymes. The biological activity of each of the principal metabolites of calcipotriol, assessed using a growth hormone reporter gene transcriptional activation system and a vitamin D receptor assay, was found to be lower than that of calcipotriol. If the extensive in vitro metabolism of calcipotriol is also found in normal and psoriatic keratinocytes in vivo, then this may explain the lack of systemic calcemic activity of topically applied drug.
 ...
PMID:In vitro metabolism of the anti-psoriatic vitamin D analog, calcipotriol, in two cultured human keratinocyte models. 810 49

Hepatitis B viruses (hepadnaviruses) can cause chronic, productive infections of hepatocytes. Analyses of the enhancers and promoters of these viruses in cell lines have suggested a requirement of these elements for liver-enriched transcription factors. In this study, a minimum of seven factor-binding sites on the duck hepatitis B virus enhancer were detected by DNase I footprinting using duck liver nuclear extracts. Among the sites that were tentatively identified were one C/EBP-, one HNF1-, and two HNF3-binding sites. Mutations of the HNF1- and HNF3-like sites, which eliminated factor binding, as assessed by both DNase I footprinting and competitive gel shift assays, were evaluated for their effects on enhancer activity. Using a construct in which human growth hormone was expressed from the viral enhancer and core gene promoter, we found that all of the mutations, either alone or in combination, reduced expression two- to fourfold in LMH chicken hepatoma cells. The mutations in the HNF1 site and one of the HNF3 sites, when inserted into the intact viral genome, also suppressed virus RNA synthesis in primary hepatocyte cultures. Virus carrying the latter HNF3 mutation was also examined for its ability to infect and replicate in ducks. No significant inhibition of virus replication was observed in a short-term assay; however, virus with the HNF3 mutation was apparently unable to grow in the pancreas, a second site of duck hepatitis B virus replication in the duck.
 ...
PMID:Identification of factor-binding sites in the duck hepatitis B virus enhancer and in vivo effects of enhancer mutations. 813 13

In the present study effects of estrogens (natural estradiol and synthetic ethinyl estradiol) on liver derived proteins (angiotensinogen, IGF-I) were investigated in vivo in ovariectomized rats and in vitro in a rat hepatoma cell line (Fe33). The aim of this study was to establish both an animal and an in vitro model for quantification of the hepatic activity of given estrogenic compounds, and to study underlying mechanisms as regards the question of direct or indirect mode of estrogen action. In ovariectomized rats subcutaneous (s.c.)-treatment for 11 days with either estradiol (E2) or ethinyl estradiol (EE) (dose range 0.1-3 micrograms/animal/day) induced a comparable dose-dependent increase in uterine weight indicating a similar estrogenic potency of the two estrogens. Equipotency was also found as regards the effects on IGF-I plasma levels which dose-dependently decreased by about 50% at the highest dose tested (3 micrograms/animal/day). The decrease in IGF-I serum levels was accompanied by a significant 40% decrease in liver IGF-I mRNA. In contrast angiotensinogen plasma levels were affected only by EE (60% increase for the 3 micrograms/animal/day dose) but not by E2. When rats, in addition to ovariectomy, were also hypophysectomized (substituted with human growth hormone and dexamethasone) angiotensinogen again increased by 80% upon administration of 3 micrograms/animal/day EE, whereas IGF-I remained unaffected by EE. In a rat hepatoma cell line (Fe33) which is stably transfected with an estrogen receptor expression plasmid, 10 nmol/l EE for 24 h caused a 2.4-fold increase in angiotensinogen mRNA level. We conclude from our studies that estrogen effects on angiotensinogen serum levels in the rat are direct effects via the hepatic estrogen receptor, whereas estrogen effects on IGF-I serum levels are indirect effects, the primary target of estrogen action being probably the pituitary. The changes in angiotensinogen serum levels in the rat model are comparable to the situation in humans indicating the rat model and the Fe33 model to be useful tools to study the hepatic activity of estrogenic compounds.
 ...
PMID:Estrogen action on hepatic synthesis of angiotensinogen and IGF-I: direct and indirect estrogen effects. 814 96

In vitro studies have shown that insulin and IGF-1 releases the fibrinolytic inhibitor plasminogen activator inhibitor-1 (PAI-1) from cells of hepatic origin. To investigate the effects of IGF-1 on fibrinolysis: 1) cultured hepatoma cells were grown in the presence of IGF-1 and media collected for secreted PAI-1 and cells probed for PAI-1 mRNA, 2) 8 hypopituitary patients were treated with recombinant human growth hormone (rhGH) and 3) 5 type 2 diabetic patients were treated with recombinant human IGF-1 (rhIGF-1). Treatment of Hep G2 cells with IGF-1 (1000 ng/ml) increased secretion of PAI-1 from a median value of 80 ng/10(6) cells (range 21-91) to 144 ng/10(6) cells (range 128-169) after 24 h (p < 0.01). Synthesis of PAI-1 mRNA increased in a similar fashion. Treatment of hypopituitary patients with rhGH led to an increase in circulating IGF-1 from a mean value of 166 (range 41-324) ng/ml at baseline to 322 (77-575) ng/ml at 4 weeks and 259 (104-533) ng/ml after 8 weeks (p < 0.02). Despite this, no changes in circulating PAI-1 or fibrinolysis occurred. Type II diabetic patients treated with rhIGF-1 showed an increase in circulating IGF-1 from a mean value of 120 ng/ml (range 109-196), at baseline to 823 ng/ml (585-894) after 5 days. This also was not associated with changes in circulating PAI-1 or in fibrinolysis. The results confirm that IGF-1 induces the synthesis of PAI-1 in Hep G2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The effects of insulin-like growth factor-1 on plasminogen activator inhibitor-1 synthesis and secretion: results from in vitro and in vivo studies. 816 92

Nucleotide sequencing of cDNAs encoding human insulin-like growth factor I (IGF-I) predicts the existence of two different prohormone forms of IGF-I. The E peptide regions extend the carboxy-terminus of the 70 amino acid core IGF-I molecule (BCAD domains) by either an additional 35 (IGF-Ia) or 77 (IGF-Ib) amino acids. Employing antiserum directed against a peptide sequence unique to the E peptide region of IGF-Ia prohormone, we have identified EIa immunoreactive material (IR-EIa) in the conditioned medium of a human hepatoma cell line, HepG2. Human growth hormone (GH) had dose-dependent stimulatory effects on IR-EIa secretion; incubation of HepG2 cells with GH at maximal concentrations (1-5 micrograms/ml) increased specific IR-EIa in 24 h conditioned medium 3-fold. The addition of human placental lactogen, insulin, IGF-I, dexamethasone, beta-estradiol, or progesterone had no significant effect. Acid chromatography of HepG2 cell conditioned medium revealed a single elution peak of IR-EIa corresponding to M(r) = 12,000-20,000. There was no immunologically detectable 7500 M(r) IGF-I peptide in acid-chromatographed conditioned medium under either basal or stimulated conditions. Biosynthetic labelling of HepG2 cell products with [35S]Trans label and immunoprecipitation with antisera specific to the E or to the AD regions of the IGF-Ia molecule indicated a single species of approx. 14,000 M(r). These data indicate that the E peptide region of IGF-Ia is translated and released as part of the larger molecule in cultured HepG2 cells, and that the levels of this prohormone are regulated by GH.
 ...
PMID:Human hepatoma cells synthesize and secrete insulin-like growth factor Ia prohormone under growth hormone control. 826 8

4-Methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione (oltipraz) and several other dithiolethiones protect against the acute toxicities of many xenobiotics and are effective inhibitors of experimental carcinogenesis. These protective effects are mediated, in part, through elevation of glutathione S-transferase, NAD(P)H: quinone reductase and UDP-glucuronosyltransferase activities in the liver and other target tissues. The induction of these phase 2 enzymes by oltiprax results from enhanced transcription. In the present study, the molecular mechanisms of these inductions were analyzed utilizing a construct containing a 41 bp enhancer element derived from the 5'-upstream region of the mouse liver glutathione S-transferase Ya subunit gene ligated to the 5' end of the isolated promoter region of this gene, and inserted into a plasmid containing a human growth hormone reporter gene. When this construct was transfected into murine Hepa 1c1c7 hepatoma cells, the concentrations of 25 dithiolethiones and related analogs required to double growth hormone production were determined and spanned a range nearly three orders of magnitude. Concentrations of dithiolethiones required to double the specific activity of NAD(P)H: quinone reductase were also determined in Hepa 1c1c7 cells. There was a positive correlation (r = 0.78) between the potencies of the 21 active compounds as inducers of both NAD(P)H: quinone reductase activity and growth hormone production. Moreover, no dithiolethiones were inactive in only one system. It is probable, therefore, that the induction of NAD(P)H: quinone reductase and other phase 2 enzymes by oltipraz and other dithiolethiones is mediated entirely through the 41 bp enhancer element.
 ...
PMID:Regulation of phase 2 enzyme induction by oltipraz and other dithiolethiones. 831 5


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