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

We have used H-35 rat hepatoma cells to test whether the type II insulin-like growth factor (IGF) receptor mediates metabolic responses to IGF-II. On the basis of both affinity cross-linking experiments and competition binding experiments, H-35 cells display insulin and type II IGF receptors, but not type I IGF receptors. IGF-II and multiplication-stimulating activity (MSA; the rat homolog of IGF-II) stimulate tyrosine aminotransferase, amino acid transport, and glycogen synthase activities to the same magnitude as insulin. However, MSA and IGF-II stimulate these metabolic responses only at high concentrations, indicating that these peptides are acting through the insulin receptor. Incubation of H-35 cells with MSA also induces a state of unresponsiveness to the further actions of both MSA and insulin. There is no associated loss of either insulin or IGF-II binding, indicating that desensitization occurs at a postbinding step in hormone action. The high concentration of MSA necessary to induce desensitization is also consistent with MSA acting through the insulin receptor. We conclude that in H-35 cells, the insulin receptor, rather than the type II IGF receptor, mediates the metabolic responses stimulated by MSA and IGF-II as well as the MSA-induced desensitization to insulin and MSA action.
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PMID:Mediation of insulin-like growth factor actions by the insulin receptor in H-35 rat hepatoma cells. 287 66

Insulin caused a rapid, dose-dependent increase in the binding of 125I-insulin-like growth factor-II (IGF-II) to the surface of cultured H-35 hepatoma cells. The [32P]phosphate content of the IGF-II receptors, immunoprecipitated from extracts of H-35 cell monolayers previously incubated with [32P]phosphate for 24 h, was decreased after brief exposure of the cells to insulin. Analysis of tryptic digests of labeled IGF-II receptors by bidimensional peptide mapping revealed that the decrease in the content of [32P]phosphate occurred to varying degrees on three tryptic phosphopeptides. Thin layer electrophoresis of an acid hydrolysate of isolated IGF-II receptors revealed the presence of [32P] phosphoserine and [32P]phosphothreonine. Insulin treatment of cells caused a decrease in the labeled phosphoserine and phosphothreonine content of IGF-II receptors. The ability of a number of highly purified protein kinases (cAMP-dependent protein kinase, protein kinase C, phosphorylase kinase, and casein kinase II) to catalyze the phosphorylation of purified IGF-II receptors was examined. Casein kinase II was the only kinase capable of catalyzing the phosphorylation of the IGF-II receptor on serine and threonine residues under the conditions of our assay. Bidimensional peptide mapping revealed that the kinase catalyzed phosphorylation of the IGF-II receptor on a tryptic phosphopeptide which comigrated with the main tryptic phosphopeptide found in receptors obtained from cells labeled in vivo with [32P]phosphate. IGF-II receptors isolated by immunoadsorption from insulin-treated H-35 cells were phosphorylated in vitro by casein kinase II to a greater extent than the receptors isolated from control cells. Similarly, IGF-II receptors from plasma membranes obtained from insulin-treated adipocytes were phosphorylated by casein kinase II to a greater extent than the receptors from control adipocyte plasma membranes. Thus, the insulin-regulated phosphorylation sites on the IGF-II receptor appear to serve as substrates in vivo for casein kinase II or an enzyme with similar substrate specificity.
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PMID:Insulin action inhibits insulin-like growth factor-II (IGF-II) receptor phosphorylation in H-35 hepatoma cells. IGF-II receptors isolated from insulin-treated cells exhibit enhanced in vitro phosphorylation by casein kinase II. 296 23

A monoclonal antibody was identified which equally inhibits 125I-labeled insulin and insulin-like growth factor I (IGF-I) binding to their respective receptors in human IM-9 lymphoid cells and solubilized placenta receptor preparations. In contrast, this monoclonal antibody inhibits insulin but not IGF-I binding to human hepatoma (HepG2) cells, fibroblasts and muscle cells. These results indicate that there are two distinct species of the type I insulin-like growth factor receptor (which we have named type IA and type IB) and suggest that this monoclonal antibody may be useful in determining whether different biological effects are mediated through these two receptors.
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PMID:Identification of a monoclonal antibody which can distinguish between two distinct species of the type I receptor for insulin-like growth factor. 301 41

Insulin treatment enhances casein kinase II (CKII) activity in 3T3-L1 mouse adipocytes and H4-IIE rat hepatoma cells, the magnitude of the activation varying from 30% to 150%. Activation of CKII was apparent after 5 min of exposure of 3T3-L1 cells to insulin, was maximal by 10 min, and persisted through 90 min. The insulin-stimulated activity was inhibited by low concentrations of heparin and was stimulated by spermine. Activation of CKII was effected by physiological concentrations of insulin (EC50 = 0.15 nM), suggesting that the effect is a true insulin response and not one mediated through insulin-like growth factor receptors. Epidermal growth factor (100 ng/ml for 10 min) also activated CKII in A431 human carcinoma cells, which is consistent with other observations that insulin and epidermal growth factor may have some common effects. Insulin stimulation of CKII activity was due to an increase in the maximal velocity of the kinase; the apparent Km for peptide substrate was not altered. Enhanced activity did not appear to result from increased synthesis of CKII protein, because cycloheximide did not block the effect and because an immunoblot developed with antiserum to CKII showed no effect of insulin on the cytosolic concentration of CKII. Because insulin-stimulated CKII activity was maintained after chromatography of cell extracts on Sephadex G-25, it is unlikely that the effect is mediated by a low-molecular-weight activator of the kinase. Rather, the results are consistent with the possibility that insulin activates CKII by promoting a covalent modification of the kinase.
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PMID:Activation of casein kinase II in response to insulin and to epidermal growth factor. 332 Oct 56

The role of the insulin receptor tyrosine kinase (protein-tyrosine kinase, EC 2.7.1.112) in various rapid insulin effects was studied by injecting four different cell types (by osmotic lysis of pinocytotic vesicles) with a monoclonal antibody that specifically inhibits the kinase activity of the insulin receptor and the closely related receptor for insulin-like growth factor (IGF)-I. Injection of this inhibitory antibody resulted in a decreased ability of insulin to stimulate the uptake of 2-deoxyglucose in Chinese hamster ovary cells and freshly isolated rat adipocytes, ribosomal protein S6 phosphorylation in CHO cells, and glycogen synthesis in the human hepatoma cell line HepG2. The ability of insulin, IGF-I, and IGF-II to stimulate glucose uptake in TA1 mouse adipocytes was also inhibited. Studies with CHO cells demonstrated that these effects of the inhibitory antibody were specific, since there was no change in phorbol ester-stimulated glucose uptake and injection of a noninhibiting antibody to the kinase had no effect on insulin action. These studies indicate that the tyrosine kinase activity of the insulin receptor is important in mediating several rapid insulin effects in a variety of different cell types.
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PMID:Acute insulin action requires insulin receptor kinase activity: introduction of an inhibitory monoclonal antibody into mammalian cells blocks the rapid effects of insulin. 354 Sep 58

The immunoglobulin fraction prepared from the serum of a rabbit immunized with purified type II insulin-like growth factor (IGF) receptor from rat placenta was tested for its specificity in inhibiting receptor binding of 125I-IGF II and for its ability to modulate IGF II action on rat hepatoma H-35 cells. The specific binding of 125I-IGF II to plasma membrane preparations from several rat cell types and tissues was inhibited by the anti-IGF II receptor Ig. Affinity cross-linking of 125I-IGF II to the Mr = 250,000 type II IGF receptor structure in rat liver membranes was blocked by the anti-receptor Ig, while no effect on affinity labeling of insulin receptor with 125I-insulin or IGF I receptor with 125I-IGF I or 125I-IGF II was observed. The specific inhibition of ligand binding to the IGF II receptor by anti-receptor Ig was species-specific such that mouse receptor was less potently inhibited and human receptor was unaffected. Rat hepatoma H-35 cells contain insulin and IGF II receptor, but not IGF I receptor, and respond half-maximally to insulin at 10(-10) M and to IGF II at higher concentrations with increased cell proliferation (Massague, J., Blinderman, L.A., and Czech, M.P. (1982) J. Biol. Chem. 257, 13958-13963). Addition of anti-IGF II receptor Ig to intact H-35 cells inhibited the specific binding of 125I-IGF II to the cells by 70-90%, but had no detectable effect on 125I-insulin binding. Significantly, under identical conditions anti-IGF II receptor Ig was without effect on IGF II action on DNA synthesis at both submaximal and maximal concentrations of IGF II. This finding and the higher concentrations of IGF II required for growth promotion in comparison to insulin strongly suggest that the Mr = 250,000 receptor structure for IGF II is not involved in mediating this physiological response. Rather, at least in H-35 cells, the insulin receptor appears to mediate the effects of IGF II on cell growth. Consistent with this interpretation, anti-insulin receptor Ig but not anti-IGF II receptor Ig mimicked the ability of growth factors to stimulate DNA synthesis in H-35 cells. We conclude that the IGF II receptor may not play a role in transmembrane signaling, but rather serves some other physiological function.
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PMID:The type II insulin-like growth factor receptor does not mediate increased DNA synthesis in H-35 hepatoma cells. 609 44

Insulin stimulates a 2-fold increase in the amount of tyrosine aminotransferase and a 5-10-fold increase in the rate of amino acid transport in dexamethasone-treated rat hepatoma cells. In order to determine whether these effects are mediated by insulin receptors or receptors for insulin-like growth factors, we have examined the binding of 125I-labeled insulin and 125I-labeled multiplication-stimulating activity, a prototype insulin-like growth factor, and compared the biological effects of these polypeptides. Insulin and multiplication-stimulating activity cause an identical increase in transaminase activity and transport velocity; half-maximal biological effects were observed at 35 ng/mg (5.5 nM) insulin and 140 ng/ml multiplication-stimulating activity. The hepatoma cells display typical insulin receptors of appropriate specificity; half-maximal displacement of tracer insulin binding occurred at 33 ng/ml unlabeled insulin, but only at 2500 ng/ml unlabeled multiplication-stimulating activity. Specific multiplication-stimulating activity receptors also were demonstrated with which insulin did not interact even at 10 micrograms/ml. Half-maximal displacement of tracer multiplication-stimulating activity occurred at 200 ng/ml unlabeled multiplication-stimulating activity. We conclude that insulin cannot act via the multiplication-stimulating activity receptor and presumably acts via typical insulin receptors. The effects of multiplication-stimulating activity on enzyme induction and amino acid transport are probably mediated primarily via the multiplication-stimulating activity receptor.
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PMID:Induction of tyrosine aminotransferase and amino acid transport in rat hepatoma cells by insulin and the insulin-like growth factor, multiplication-stimulating activity. Mediation by insulin and multiplication-stimulating activity receptors. 610 9

Insulin-like growth factor II (IGF II) regulated tissue-specific gene expression in hepatoma cell lines, but had no effect on expression of tissue-specific genes in primary cultures of E14 and newborn rat liver cells depleted of erythroid cells. No change was observed in these primary cultures with respect to alpha-fetoprotein (alpha-FP), albumin, cytokeratin 19 (CK19), gamma-glutamyltranspeptidase (GGT), and IGF II receptors. Two well-differentiated hepatoma, HepG2 and FTO-2B, and a poorly differentiated hepatoma, H4AzC2, did not show increased proliferation in the presence of IGF II, yet showed gene expression changes in response to IGF II. In HepG2 cells, IGF II increased albumin mRNA levels and resulted in a shift from clusters of cells positive to 100% of the cells expressing immunohistochemically detectable albumin. The transcription factor HNF-3 beta mRNA and protein levels of the bile duct markers, CK19 and GGT, were also increased in the presence of IGF II. Other genes tested were not affected, including alpha-1-antitrypsin, and two liver-specific transcription factors, HNF-4 and HNF-3 alpha. In FTO-2B cells, IGF II increased the expression of albumin, CK19, and GGT, without accompanying changes in albumin and GGT mRNAs. In H4A7C2 cells, IGF II reduced CK19 and OC.3 protein levels and GGT, transferrin, and HNF-3 beta mRNAs. The effects of IGF II on H4AZC2 cells were not blocked in the presence of an anti-rat IGF II receptor antibody. We conclude that IGF II affects tissue-specific gene expression of hepatomas and qualitative and quantitative aspects of its influence on the hepatomas is dependent on their degree of differentiation.
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PMID:Insulin-like growth factor II regulation of gene expression in rat and human hepatomas. 752 37

The rate of transcription of the hepatic phosphoenolpyruvate carboxykinase (PEPCK) and insulin-like growth factor-binding protein 1 (IGFBP-1) genes is stimulated by glucocorticoids and inhibited by insulin. In both cases, the effect of insulin is dominant, since it suppresses both basal and glucocorticoid-stimulated PEPCK or IGFBP-1 gene transcription. Analyses of both promoters by transfection of PEPCK or IGFBP-1-chloramphenicol acetyltransferase fusion genes into rat hepatoma cells has led to the identification of insulin response sequences (IRSs) in both genes. The core IRS, T(G/A)TTTTG, is the same in both genes, but the PEPCK promoter has a single copy of this element whereas the IGFBP-1 promoter has two copies arranged as an inverted palindrome. The IGFBP-1 IRS and PEPCK IRS both bind the alpha and beta forms of hepatic nuclear factor 3 (HNF-3), although the latter does so with a sixfold-lower relative affinity. Both the PEPCK and the IGFBP-1 IRSs also function as accessory factor binding sites required for the full induction of gene transcription by glucocorticoids. A combination of transient transfection and DNA binding studies suggests that HNF-3 is the accessory factor that supports glucocorticoid-induced gene transcription. In both genes, the HNF-3 binding site overlaps the IRS core motif(s). A model in which insulin is postulated to mediate its negative effect on glucocorticoid-induced PEPCK and IGFBP-1 gene transcription indirectly by inhibiting HNF-3 action is proposed.
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PMID:Hepatic nuclear factor 3- and hormone-regulated expression of the phosphoenolpyruvate carboxykinase and insulin-like growth factor-binding protein 1 genes. 753 83

In biological fluids, insulin-like growth factor binding proteins (IGFBPs) interact with the IGFs and modulate their effects. In this study, changes in IGFBP-1 expression were investigated under the influence of insulin and cAMP which may regulate expression of the IGFBP-1 gene in vivo during the perinatal period. Western ligand blot analysis of IGFBPs secreted by HepG2 human hepatoma cells showed that 24 h treatment with forskolin increased IGFBP-1 secretion by approximately 100%, whereas similar treatment with insulin resulted in a 50% reduction. After 24 h, the amounts of IGFBP-1 mRNA (measured by Northern blotting) were increased 2.5 times by forskolin and decreased by 65% by insulin. Transient transfection experiments showed that forskolin enhanced IGFBP-1 promoter activity by 70%, suggesting that stimulation of IGFBP-1 gene expression by cAMP is transcriptional, via a protein recognizing the cAMP responsive element (CRE) consensus sequence (nt -268 to -248). In contrast, modulation of gene expression by insulin is more complex, probably involving several levels of regulation. Complementary experiments (site-directed mutagenesis and/or use of a heterologous promoter) will be needed to confirm the functionality of the proteins interacting with the IRE (nt -285 and -276) and the CRE (between nt -268 and -248) described.
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PMID:Transcriptional regulation of insulin-like growth factor binding protein-1 expression by insulin and cyclic AMP. 754 54


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