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)

Haemopexin receptors from mouse hepatoma (Hepa) cells were affinity-labelled by cross-linking to haem-125I-haemopexin complexes using two homo-[disuccinimidyl suberate (DSS) and 3,3'-dithiobis(succinimidyl propionate) (DTSSP)] and one hetero-[sulphosuccinimidyl 4-(p-maleimidophenyl)butyrate (sulpho-SMPB)] bifunctional cross-linking agents. Analysis of the cross-linked products by SDS/PAGE in the absence of reducing agents revealed that 125I-haemopexin was cross-linked specifically to a protein of apparent molecular mass 85-90 kDa. Upon reduction, haemopexin remained cross-linked to a protein of 20 kDa, suggesting that the murine haemopexin receptor has a subunit structure. Two subunits were identified: alpha (p65) and beta (p20). Furthermore, because haemopexin was cross-linked by all three agents to p20, the shortest cross-linker arm being 1.1 nm (11 A), we propose that the haem-haemopexin-binding site resides on this subunit. In addition, a cysteine residue of p20 is located near the haemopexin-binding site, since haemopexin, which has no free thiol groups, is cross-linked to this subunit by the hetero-bifunctional agent sulpho-SMPB. Exposure of Hepa cells to the tumour-promoting phorbol ester 4 alpha-phorbol 12-myristate 13-acetate (PMA) causes a rapid redistribution of haemopexin receptors from the cell surface to the cell interior. Within 2-4 min of incubation with 100 nM-PMA, there was an approx. 50% decrease in cell-surface haemopexin receptors, as judged by ligand binding at 0 degrees C and affinity labelling of the receptor. This time- and dose-dependent down-regulation was fully reversible within 60-90 min after removal of PMA, and the affinity of the remaining receptors was unaltered by PMA. The specificity of PMA was demonstrated by comparison with the non-tumour-promoter 4 alpha-phorbol, which did not affect any of the parameters examined. The amine H-7, a specific inhibitor of protein kinase C, antagonised the receptor redistribution effect of PMA, suggesting that the down-regulation of haemopexin receptors on the cell surface was a consequence of protein kinase C activation. The PMA-induced decrease in surface haemopexin receptors was due to a 2-fold increase in the rate of internalization (from 0.73 min-1 to 1.32 min-1), whereas the rate of exocytosis (0.6 min-1) was unchanged. PMA treatment, like binding of the natural ligand, haem-haemopexin, results in a lower steady-state level of surface haemopexin receptors independent of receptor synthesis, and the receptors were not degraded but were recycled back to the cell surface.
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PMID:The murine haemopexin receptor. Evidence that the haemopexin-binding site resides on a 20 kDa subunit and that receptor recycling is regulated by protein kinase C. 164 99

Mouse serum amyloid A proteins (SAA) are encoded by multiple genes and the expression of these SAA genes is highly induced during inflammation. We demonstrate that the expression of one of SAA genes (SAA3) is induced by interleukin-1 (IL-1), and that other inflammatory cytokines such as IL-6 and leukemia inhibitory factor, while they themselves are without any effects, enhanced IL-1 induced SAA3 gene expression. The results of mutational analysis on the SAA3 promoter indicate that both the NF-kappa B and C/EBP transcription factor-binding motifs are essential for cytokine-induced SAA3 gene expression in Hep3B cells. To study further roles of NF-kappa B and C/EBP transcription factor family members in SAA3 gene activation, expression vectors for NF-kappa B subunits (p50 and p65) and C/EBP family members (C/EBP-alpha and NFIL-6, also called C/EBP-beta) were co-transfected into Hep3B hepatoma and F9 embryonic carcinoma cells. The results show that, while the expression of p65 alone strongly transactivated a SAA3 gene, p50 did not induce a significant transactivation, and NFIL-6 and C/EBP-alpha induced only a marginal transactivation when expressed alone. However, the co-expression of p50 or p65 with C/EBP family members did result in the efficient induction of SAA3 gene expression, indicating that the synergy between NF-kappa B and C/EBP transcription factor families is essential for SAA3 gene expression during inflammation.
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PMID:NF-kappa B and C/EBP transcription factor families synergistically function in mouse serum amyloid A gene expression induced by inflammatory cytokines. 795 7

To understand the mechanisms by which large increases in serum amyloid A (SAA) occur during the acute phase response, human hepatoma cells were transfected with SAA2 gene reporter plasmids and stimulated with combinations of cytokines. Although interleukin-1 (IL-1) and interleukin-6 (IL-6) stimulated transcription from this promoter individually, addition of both mediators produced a response between two and nine times greater than the expected additive response. This synergistic activation was dependent on the integrity of at least two cis-acting sequences in the SAA2 enhancer. The SAA2 NF-kappa B site was required functionally for the response to both IL-1 and IL-6 alone as well as for synergistic activation; however, IL-6 did not directly induce binding of nuclear proteins to the NF-kappa B sequence. A NF-IL6 site was required for full induction by IL-1 and IL-6, and also mediated strong transactivation by recombinant NF-IL6. Furthermore, transfected NF-IL6 synergized strongly with co-transfected NF-kappa B, particularly with RelA (p65). However synergy between IL-1 and IL-6 was only partly reduced by mutation of the NF-IL6 site, indicating further levels of interaction in addition to the NF-kappa B/NF-IL6 cooperativity.
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PMID:The role of NF-kappa B and NF-IL6 transactivating factors in the synergistic activation of human serum amyloid A gene expression by interleukin-1 and interleukin-6. 824 97

Tyrosine phosphorylation of cellular proteins is an early and key step after activation of the insulin receptor kinase (IRK). The study of the properties of these proteins should contribute to our understanding of insulin action. In rat hepatoma cells overexpressing human insulin receptors (HTC-IR), insulin treatment resulted in rapid tyrosine phosphorylation of proteins of 180, 94, 68, and 60 kDa. When lysates from insulin-treated cells were immunoprecipitated with anti-Syp antibody, subsequent immunoblotting identified p65 and p68, which reacted with anti-Syp, and p6O and p68, which reacted with antiphosphotyrosine antibody. Thus, insulin treatment yielded tyrosine phosphorylation of both Syp and a Syp-associated p6O molecule. When lysates from insulin-treated cells were adsorbed with a glutathione S-transferase (GST)-Syp-Src homology-2 (SH2) fusion protein, tyrosine- phosphorylated p6O was sequestered. After subjecting lysates to SDS-PAGE, the GST-SypSH2 fusion protein was found to bind to p18O, p94, and p6O. Thus, Syp associates directly with a 60-kDa IRK substrate via its SH2 domains. Syp-associated p6O differed from the 60- to 62-kDa proteins, associating with ras guanosine triphosphatase-activating protein, which also underwent modest tyrosine phosphorylation in response to insulin. Preadsorption of cell lystates with antibody against the 85-kDa subunit (p85) of phosphatidylinositol 3-kinase substantially reduced the amount of p60 subsequently immunoprecipitated by anti-Syp. Thus, p60 associates with both Syp and p85. The amount of tyrosine-phosphorylated p60 exceeded that of p180 in anti-Syp immunoprecipitates, whereas their proportion was comparable in anti-p85 immunoprecipitates. Grb2 was also observed in the anti-Syp immunoprecipitates. When lysates from insulin-treated cells were adsorbed with GST-p85SH2 domains or GST-Grb2, the subsequent eluates contained tyrosine-phosphorylated p60, as determined by immunoblotting with antiphosphotyrosine. Membrane binding assays using GST fusion proteins showed that these associations were direct. Studies in rat liver, muscle, and adipose tissue identified insulin-dependent association of Syp, Grb2, and p85 with tyrosine-phosphorylated p60 in adipose tissue only. We conclude that insulin treatment of HTC-IR cells and rat adipose tissue results in the tyrosine phosphorylation of p60, which might participate in the recruitment of downstream effectors involved in insulin signal transduction.
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PMID:A 60-kilodalton protein in rat hepatoma cells overexpressing insulin receptor was tyrosine phosphorylated and associated with Syp, phophatidylinositol 3-kinase, and Grb2 in an insulin-dependent manner. 877 Aug 81

The "long pentraxins" are an emerging family of genes that have conserved in their carboxy-terminal halves a pentraxin domain homologous to the prototypical acute phase protein pentraxins (C-reactive protein and serum amyloid P component) and acquired novel amino-terminal domains. In this report, a genomic fragment of 1371 nucleotides from the human "long pentraxin" gene PTX3 is characterized as a promoter on tumor necrosis factor-alpha (TNFalpha) and interleukin (IL)-1beta exposure in transfected 8387 human fibroblasts by chloramphenicol acetyltransferase and RNase protection assays. In the same cells, the PTX3 promoter does not respond to IL-6 stimulation. Furthermore, IL-1beta and TNFalpha responsiveness is not seen in the Hep 3B hepatoma cell line. The minimal promoter contains one NF-kappaB element which is shown to be necessary for induction and able to bind p50 homodimers and p65 heterodimers but not c-Rel. Mutants in this site lose the ability to bind NF-kappaB proteins and to respond to TNFalpha and IL-1beta in functional assays. Sp1- and AP-1 binding sites lying in proximity to the NF-kappaB site do not seem to play a major role for cytokine responsiveness. Finally, cotransfection experiments with expression vectors validate that the natural promoter contains a functional NF-kappaB site.
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PMID:Characterization of the promoter for the human long pentraxin PTX3. Role of NF-kappaB in tumor necrosis factor-alpha and interleukin-1beta regulation. 907 34

The expression of P-glycoproteins encoded by the mdr gene family is associated with the emergence of multidrug resistance phenotype in animal cells. However, the mechanisms controlling the expression of these genes have not been well elucidated. Here, we report that the expression of rat mdr1b gene in cultured H-4-II-E hepatoma cells can be induced by insulin. Transient transfection assays using reporter gene constructs containing various 5' mdr1b sequences showed that the sequence located between base pairs -243 and -163 is important for insulin's induction of mdr1b promoter activity. Further analyses revealed that a NF-kappaB-binding site (located between base pairs -167 and -158) is required for insulin-induced promoter activity. Gel mobility shift assay demonstrated that insulin stimulates the binding of nuclear p50/p65 subunits to the mdr1b NF-kappaB sequence. Cotransfection of plasmids expressing either the p50/p65 NF-kappaB subunits or Raf-1 kinase or both resulted in increased expression of the gene containing wild-type but not NF-kappaB site-mutated mdr1b promoter. Finally, expression of either the antisense p65 subunit of NF-kappaB or dominant negative Raf-1 kinase blocked insulin's induction of the mdr1b promoter activity. Taken together, our results suggest that the insulin-induced mdr1b expression is mediated by transcription factor NF-kappaB via the Raf-1 kinase signaling pathway.
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PMID:NF-kappaB-mediated induction of mdr1b expression by insulin in rat hepatoma cells. 918 39

We have tested the expression of a 65-kDa oncofetal protein (p65) after combined treatment with menadione and methotrexate in hamsters transplanted with Kirkman-Robins hepatoma. The treatment of tumor-bearing animals with these compounds significantly inhibited both the tumor development and the expression of p65. This inhibition in tumor tissue was calculated from densitograms of Western blots. The inhibition of p65 expression was also confirmed in the serum of hepatoma bearing animals by using solid-phase radioimmunoassay (RIA) to quantify the specificity of polyclonal antibodies to fetal p65 molecules. Additionally, p65 was shown to localize both in cytoplasm and in the nuclear extracts prepared from hepatoma tissue.
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PMID:Expression of 65-kDa oncofetal protein in experimental hepatoma after anticancer therapy. 920 Dec 86

In fibroblasts and hepatoma cells, interleukin-1 (IL-1) treatment results in the rapid nuclear accumulation of the transcription factor NF-kappaB, present largely as p65 (RelA)/p50 heterodimers. It is well established that this process is dependent in large part upon the phosphorylation and subsequent degradation of the cytosolic inhibitor IkappaB. We looked for other IL-1-induced modifications of NF-kappaB components and found that, in both cell types, IL-1 stimulation led, within minutes, to phosphorylation of both NF-kappaB p65 and p50. Phosphorylation of p65 was sustained for at least 30 min after addition of the cytokine and occurred principally upon serine residues. Immunoprecipitates of NF-kappaB complexes contained an associated protein kinase, the biochemical characteristics of which were indistinguishable from casein kinase II (CKII). Purified CKII efficiently phosphorylated p65 in vitro, apparently on the same major sites that became phosphorylated in intact IL-1-treated cells. Although IL-1 treatment caused little apparent stimulation of total cellular CKII activity, the fraction that was specifically associated with NF-kappaB complexes was markedly elevated by the cytokine. The association of CKII with NF-kappaB occurred in the cytoplasm, suggesting that this phosphorylation might be involved either in control of translocation of the activated complex or in modulation of its DNA binding properties.
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PMID:Activation of nuclear transcription factor NF-kappaB by interleukin-1 is accompanied by casein kinase II-mediated phosphorylation of the p65 subunit. 940 76

Interleukin 6 (IL-6) is a pleiotropic cytokine that induces many biological activities, including some aspects of the immune reaction and inflammatory responses. In the liver, IL-6 regulates the synthesis of a broad spectrum of acute-phase proteins. IL-6 is also known to be a factor involved in the immunoregulatory perturbations in patients with chronic liver diseases (CLDs). Here, we report that IL-6 can be induced by hepatitis B virus (HBV)-X protein, as evidenced by high levels of serum IL-6 in patients with CLD with HBV infection, IL-6 productions observed in HBV-X-transfected cells, and transcriptional transactivations of the IL-6 gene by HBV-X. We determined serum levels of IL-6 in patients with chronic hepatitis B (CH-B), chronic hepatitis C (CH-C), liver cirrhosis (LC) caused by hepatitis B, and LC with hepatocellular carcinoma (HCC) caused by hepatitis B (LC+HCC). Mean serum levels of IL-6 in all CLD patients were higher than those in normal controls, and the difference was statistically significant (P < 0.05). Mean IL-6 levels of LC and LC+HCC patients were significantly higher than those of CH-B patients (P < 0.05). Because the etiological factor in all cases except CH-C (CH-B, LC, and LC+HCC) was HBV, we checked the possibility of HBV-transactivator-X activation of IL-6 promoter. Using deletion constructs of 5'-flanking regulatory regions of the IL-6 gene linked to the chloramphenicol acetyltransferase gene as a reporter, we found that the binding of nuclear factor-kappaB to a cis element is essential and sufficient for the induction of the IL-6 gene by HBV-X. We also found that HBV-X enhances the binding of two subunits of nuclear factor-kappaB (p65 and p52) to their target DNA binding sequences. These observations are relevant, in that HBV-X might play an important role in hepatic inflammation and diseases by up-regulating IL-6 production, which can eventually lead to LC and HCC.
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PMID:Human interleukin 6 gene is activated by hepatitis B virus-X protein in human hepatoma cells. 967 46

The transcriptional regulation of the fibronectin (FN) gene in hepatoma cells by phorbol myristate acetate (PMA) was investigated. PMA increased the synthesis and mRNA levels of FN and its promoter activity in Hep3B hepatoma cells. The PMA-induced activation of FN expression was blocked by a protein kinase C (PKC) inhibitor and did not require a new protein synthesis. Deletion analysis revealed that the sequence between positions -69 and +136 of the FN gene was responsible for the PMA induction. Two PMA-inducible nuclear protein complexes were found to bind to a putative NF-kappaB site at -41 and were identified as a p65/p50 heterodimer and a p50/50 homodimer of NF-kappaB family. Mutations in the -41 NF-kappaB site, however, did not block the PMA induction of the FN promoter but rather enhanced it. Overexpression of p65 increased the FN promoter activity. While overexpression of p50 alone did not affect the promoter activity, it decreased the p65-induced activation of the FN promoter. Mutations in the -41 NF-kappaB site attenuated the p50-mediated suppression of the p65 transactivation of the FN promoter. Deletion of the sequence between +1 and +136 decreased the basal and PMA-induced activities of the FN promoter. This study shows that PMA induces the transcription of the FN gene in hepatoma cells via the PKC pathway. The DNA sequence between +1 and +136 is responsible, at least in part, for the PMA-induced activation of the FN gene, while the -41 NF-kappaB binding site plays as a negative regulatory element for it. In addition, this study is the first to show a role for NF-kappaB p65 in the transcriptional activation of the FN gene.
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PMID:Transcriptional regulation of fibronectin gene by phorbol myristate acetate in hepatoma cells: a negative role for NF-kappaB. 1064 41


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