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)

Using RNA blot analysis, we examined the relatedness of gene expression of several rat ascites hepatoma lines (AH) to azo-dye-induced primary hepatomas (PH). Four cDNA clones previously defined as containing sequences abundantly expressed in various tumor lines showed virtually the same pattern on both RNA blots of an AH line, AH60C and of PH, thereby indicating that the tumor-abundant expression of the sequences is also well retained in PH. Expression of ras and myc oncogenes in AH was the same as that in PH. However, liver-specific mRNAs such as albumin and apoprotein A-1 mRNA were expressed in normal liver and PH, but to a much lesser extent in AH60C. alpha-Fetoprotein was expressed in PH, but little in the normal liver and, if any, very little in AH60C. alpha 2u-Globulin was not expressed in either AH60C or PH. Semiquantitative RNA dot blot analyses revealed that the different expressions of certain genes between AH60C and PH observed above also hold true, even in case of other AH lines and a solid tumor line, Morris hepatoma 5123D. Southern blot analyses of the genomic DNAs showed that the different expressions might have occurred, with no major alteration in the gene structure.
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PMID:Difference in gene expression between azo-dye-induced primary hepatomas and corresponding transplantable ascites hepatoma lines in rats. 244 19

A total of six established human hepatoma-derived cell lines, including Hep3B, NPLC/PRF/5 (NPLC), Tong/HCC, Hep 10, huH1, and huH2, were screened for their ability to accumulate significant quantities of lipoproteins in serum-free medium. Only two cell lines, Hep3B and NPLC, secreted quantitatively significant amounts of lipoproteins. In a 24-h period the accumulated mass of apolipoproteins (apo) A-I, A-II, B, and E and albumin for Hep3B cells was 1.96, 1.01, 1.96, 1.90, and 53.2 micrograms/mg cell protein per 24 h, respectively. NPLC cells secreted no detectable albumin but the 24-h accumulated mass for apolipoproteins A-I, A-II, B, and E was 0.45, 0.05, 0.32, and 0.68 micrograms/mg cell protein per 24 h, respectively. Twenty four-hour serum-free medium of Hep3B cells contained lipoproteins corresponding to the three major density classes of plasma; percent protein distribution among the lipoprotein classes was 4%, 41%, and 56% for very low density lipoprotein ("VLDL"), low density lipoprotein ("LDL"), and high density lipoprotein ("HDL"), respectively. NPLC was unusual since most of the lipoprotein mass was in the d 1.063-1.235 g/ml range. Hep3B "LDL", compared with plasma LDL, contained elevated triglyceride, phospholipid, and free cholesterol. Nondenaturing gradient gel electrophoresis revealed that Hep3B "LDL" possessed a major component at 25.5 nm and a minor one at 18.3 nm. Immunoblots showed that the former contained only apoB while the latter possessed only apoE. Like plasma VLDL, Hep3B "VLDL" particles (30.5 nm diameter) isolated from serum-free medium contained apoB, apoC, and apoE. "HDL" harvested from Hep3B and NPLC medium were enriched in phospholipid and free cholesterol and poor cholesteryl ester which is similar to the composition of HepG2 "HDL." "HDL" from Hep3B and NPLC culture medium on gradient gel electrophoresis had peaks at 7.5, 10, and 11.9 nm which were comparable to major components found in HepG2 cell medium. Hep3B cells, in addition, possessed a particle that banded at 8.2 nm which appeared to be an apoA-II without apoA-I particle by Western blot analysis. The cell line also produced a subpopulation of larger-sized "HDL" not found in HepG2 medium. NPLC "HDL" had a distinct peak at 8.3 nm which by Western blot was an apoE-only particle. Electron microscopy revealed that "HDL" harvested from Hep3B and NPLC medium consisted of discoidal and small, spherical particles like those of HepG2. The "HDL" apolipoprotein content of each cell line was distinct from that of HepG2. ApoA-II at 35% of apolipoprotein distinguishes Hep3B "HDL" from HepG2, which contains only 10%.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Isolation and characterization of lipoproteins produced by human hepatoma-derived cell lines other than HepG2. 255 86

The rat hepatoma cell line Fu5AH has the unusual property of accumulating massive amounts of cholesteryl ester upon incubation with hypercholesterolemic serum, and especially when incubated with beta-very low density lipoproteins (beta-VLDL) from cholesterol-fed dogs. The present study was designed to identify and characterize the lipoprotein receptors that mediate the cholesteryl ester accumulation. The beta-VLDL and cholesterol-induced apolipoprotein (apo) E-containing high density lipoproteins (apoE HDLc) bound to Fu5AH cells with very high affinity (Kd approximately equal to 10(-10) M), whereas low density lipoproteins (LDL) bound with unusually low affinity (Kd approximately equal to 10(-8) M). Receptor binding activity of 125I-labeled beta-VLDL, 125I-labeled apoE HDLc, and 125I-labeled LDL was abolished by incubation in the presence of an excess of unlabeled LDL or of a polyclonal antibody to the bovine adrenal apoB,E(LDL) receptor. The receptors were completely down-regulated by preincubating Fu5AH cells with beta-VLDL, but much higher levels of beta-VLDL were required than for down-regulation of fibroblast apoB,E(LDL) receptors. Receptor binding was abolished by reductive methylation of the lysyl residues of the apolipoprotein of the beta-VLDL and by an apoE monoclonal antibody (1D7) that blocks receptor binding. The Fu5AH receptor was further characterized by using the bovine adrenal apoB,E(LDL) receptor antibody. A single protein (Mr approximately equal to 130,000) was identified in Triton extracts of whole cells, and two proteins (Mr approximately equal to 130,000 and 115,000) were found in Fu5AH cell membranes disrupted by homogenization. The Mr approximately equal to 115,000 protein was released from the membranes and did not react with an antibody to the carboxyl-terminal (cytoplasmic) domain of the apoB,E(LDL) receptors. These studies indicate that Fu5AH cells express apoB,E(LDL) receptors that have unusually low affinity for apoB-continuing lipoproteins, require large amounts of cholesterol to induce down-regulation, and are susceptible to specific proteolysis in cell homogenates. These apoB,E(LDL) receptors are responsible for the receptor-mediated uptake of beta-VLDL and chylomicron remnants by Fu5AH cells.
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PMID:Characterization of lipoprotein receptors on rat Fu5AH hepatoma cells. 282 2

The regulation of lipoprotein assembly and secretion at a molecular level is incompletely understood. To begin to identify the determinants of apoprotein synthesis and distribution among lipoprotein classes, we have examined the effects of chylomicron remnants which deliver triglyceride and cholesterol, and beta very low density lipoprotein (beta VLDL), which deliver primarily cholesterol, on apolipoprotein synthesis and secretion by the human hepatoma Hep G2. Hep G2 cells were incubated with remnants or beta VLDL for 24 h, the medium was changed and the cells then incubated with [35S]methionine. The secreted lipoproteins were separated by gradient ultracentrifugation and the radiolabeled apoproteins were isolated by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and counted. Remnants caused a 14-fold, and beta VLDL a 7-fold, increase in VLDL apoprotein (apo) secretion; the apoB/apoE ratio in this class was unchanged. Preincubation with either of the lipoproteins also stimulated low density lipoprotein apoB secretion. Preincubation with beta VLDL, but not with remnants, significantly increased apoE and apoA-I secreted in high density lipoprotein (HDL). In addition, the apoE/apoA-I ratio precipitated from the HDL of beta VLDL-treated cells by anti-apoE was 2.2-fold higher than that precipitated by anti-apoA-I. There was no difference in the ratios precipitated from control HDL. This was due to the secretion of a lipoprotein, subsequently isolated by immunoaffinity chromatography, that contained predominantly apoE. When Hep G2 cells were preincubated with oleic acid alone, total apoprotein secretion was not altered. However, cholesterol-rich liposomes stimulated secretion of newly synthesized apoE, but not apoB, while apoA-I secretion was variably affected. Cholesterol-poor liposomes had no effect. Thus, lipid supply is a determinant of apoprotein synthesis and secretion, and cholesterol may be of particular importance in initiating apoprotein synthesis.
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PMID:Regulation of apoprotein synthesis and secretion in the human hepatoma Hep G2. The effect of exogenous lipoprotein. 284 42

The consumption of long chain polyunsaturated fatty acids by fish oils leads to profound lowering of plasma triacylglycerol but not of plasma cholesterol. Reasons for this were investigated with the human hepatoma cell line, the Hep G2 cell. Incubations with oleic acid (18:1 n9), linoleic acid (18:2 n6) and the characteristic marine fatty acid eicosapentaenoic acid (EPA, 20:5 n3) enriched cellular triacylglycerol mass, though least with EPA. However, secretion of very low density lipoprotein (VLDL) triacylglycerol and apoprotein B (measured by formation from [3H]glycerol and [3H]leucine) was markedly inhibited by EPA. Preincubation with linoleic acid reduced VLDL triacylglycerol but not apo B secretion in comparison with oleic acid which stimulated both. A possible effect on low density lipoprotein (LDL) removal was studied by measuring [125I]LDL binding. Preincubation with either EPA or linoleic acid inhibited the saturable binding of LDL, observed with oleic acid and control incubations. The binding of lipoproteins containing chylomicron remnants was not affected by any of the fatty acids.
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PMID:Eicosapentaenoic acid inhibits the secretion of triacylglycerol and of apoprotein B and the binding of LDL in Hep G2 cells. 303 33

The role of the low density lipoprotein (LDL) receptor in the binding of chylomicron remnants to liver membranes and in their uptake by hepatocytes was assessed using a monospecific polyclonal antibody to the LDL receptor of the rat liver. The anti-LDL receptor antibody inhibited the binding and uptake of chylomicron remnants and LDL by the poorly differentiated rat hepatoma cell HTC 7288C as completely as did unlabeled lipoproteins. The antireceptor antibody, however, decreased binding of chylomicron remnants to liver membranes from normal rats by only about 10%. This was true for intact membranes and for solubilized reconstituted membranes and with both a crude membrane fraction as well as with purified sinusoidal membranes. Further, complete removal of the LDL receptor from solubilized membranes by immunoprecipitation with antireceptor antibody only decreased remnant binding to the reconstituted supernatant by 10% compared to solubilized, nonimmunoprecipitated membranes. Treatment of rats with ethinyl estradiol induced an increase in remnant binding by liver membranes. All of the increased binding could be inhibited by the antireceptor antibody. The LDL receptor-independent remnant binding site was not EDTA sensitive and was not affected by ethinyl estradiol treatment. LDL receptor-independent remnant binding was competed for by beta-VLDL = HDLc greater than rat LDL greater than human LDL (where VLDL is very low density lipoprotein, and HDL is high density lipoprotein). There was weak and incomplete competition by apoE-free HDL, probably due to removal of apoE from the remnant. The LDL receptor-independent remnant-binding site was also present in membranes prepared from isolated hepatocytes and had the same characteristics as the site on membranes prepared from whole liver. In contrast, when chylomicron remnants were incubated with a primary culture of rat hepatocytes, the anti-LDL receptor antibody prevented specific cell association by 84% and degradation of chylomicron remnants completely. Based on these studies, we conclude that although binding of chylomicron remnants to liver cell membranes is not dependent on the LDL receptor, their intact uptake by hepatocytes is.
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PMID:Role of low density lipoprotein receptor-dependent and -independent sites in binding and uptake of chylomicron remnants in rat liver. 317 May 77

We have shown that the Fao cell, a differentiated rat hepatoma line, is an excellent model for the study of the synthesis of lipoproteins (Scarino, M L & Howell, K E, Exp cell res 170 (1987) 1 [1]. Here we demonstrate that variation of the lipid composition of the growth medium significantly modulates the composition and quantity of particles formed. Three growth conditions were compared: normal, lipid-depleted, and lipid-supplemented. The synthesis of both the protein and lipid moieties of the lipoproteins was quantitated using the radioactive metabolic precursors [35S]methionine and [14C]acetate. The total secretion of the cells was collected and fractionated into four density classes equivalent to plasma lipoproteins and a bottom fraction equivalent to plasma proteins. Each density class was evaluated for the apoprotein distribution after separation by SDS-PAGE and for lipid distribution and composition after lipid extraction. ApoE accounts for approx. 15% of the total protein synthesized and is the major apoprotein. The amount synthesized remains relatively constant under all growth conditions. In contrast, the amount of apoB synthesis varies over 600-fold. In lipid-depleted conditions, only 0.01 times the normal amount was synthesized, while in lipid-supplemented conditions 6.2 times the normal amount was synthesized. ApoB was associated with the lighter fraction; therefore the modulation increased the quantity of low-density particles formed. A similar but far less pronounced variation of the heavier particles and the apoA-I concentration was obtained. Under lipid-depleted conditions, 0.75 times the normal amount was synthesized, while under lipid-supplemented conditions 2.6 times the normal quantity was synthesized.
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PMID:The Fao cell. A tissue culture model for lipoprotein synthesis and secretion. II. Modulation by lipid depletion and supplementation. 356 29

The uptake and internalization of a triglyceride emulsion by rat hepatocytes in culture less than 24 hr was either inhibited or uninfluenced by apoE. ApoE significantly increased the uptake of these emulsions in later cultures. Specific low density lipoprotein (LDL) binding was similar for hepatocyte monolayers prior to and after 24 hr. Rat hepatocytes in culture for 2 days, which were treated with collagenase, detached and then replated within 1 hr and were apoE-responsive in 2 hr. Heparin inhibited the apoE stimulation in both hepatocytes and hepatoma monolayers. Heparin wash of hepatocytes or hepatoma cells incubated with apoE-[14C]triolein emulsions at 4 degrees C resulted in a considerable loss in radiolabeled cell lipid. A similar wash after 37 degrees C incubations produced little loss suggesting internalization. Hepatocytes had lower affinity but similar apoE-emulsion binding capacity compared to hepatoma cells. Triolein emulsions with apoE were significantly more rapidly metabolized by the hepatocyte than unsupplemented emulsions. The apoE-mediated hepatocyte lipid uptake was inhibited by apoC proteins. High molar ratios of free fatty acid/albumin also suppressed hepatocyte apoE-mediated lipid uptake. Both rat high density lipoprotein (HDL) and LDL inhibited with a potency directly related to their content of apoE. Human LDL and HDL without apoE also inhibited the interaction with less potency than the rat lipoproteins. Human HDL inhibition was diminished after removal of apoC proteins.
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PMID:Effect of apoE on triglyceride emulsion interaction with hepatocyte and hepatoma G2 cells. 362 37

Oncomodulin, the parvalbumin-like calcium-binding protein frequently expressed in tumor tissue, was isolated from Morris hepatoma 5123tc and studied using the luminescent lanthanide ions, Eu3+ and Tb3+. Titrations of the apoprotein - whether monitored by indirect excitation of bound Tb3+, by direct laser excitation of bound Eu3+, or by quenching of the intrinsic tyrosine fluorescence - all indicated the presence of two high-affinity binding sites for lanthanide ions, as in parvalbumin. Moreover, the appearance of the Eu3+ 7F0----5D0 excitation spectrum of Eu2-oncomodulin was found to be highly pH-dependent, as previously observed with parvalbumin. At pH 5.0, it consists of a single peak centered at 5796 A, having a linewidth of approximately 6 A. At higher pH values, this spectrum is replaced by a broader, more symmetric peak at 5782 A. Oncomodulin, however, was found to differ from parvalbumin in at least one important respect: In contrast to the muscle-associated protein, the affinities of the CD site in oncomodulation for Tb3+ and Ca2+ were found to be rather similar, with KCa/KTb approximately equal to 11 +/- 2.
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PMID:Lanthanide-binding properties of rat oncomodulin. 373 Mar 94

Hepatic lipase can enhance the delivery of high-density lipoprotein (HDL) cholesterol to cells by a process which does not involve apoprotein catabolism. The incorporation of HDL-free (unesterified) cholesterol, phospholipid, and cholesteryl ester by cells has been compared to establish the mechanism of this delivery process. Human HDL was reconstituted with 3H-free cholesterol and [14C]sphingomyelin, treated with hepatic lipase in the presence of albumin to remove the products of lipolysis, reisolated, and then incubated with cultured rat hepatoma cells. Relative to control HDL, modification of HDL with hepatic lipase stimulated both the amount of HDL-free cholesterol taken up by the cell and the esterification of HDL-free cholesterol but did not affect the delivery of sphingomyelin. Experiments utilizing HDL reconstituted with 14C-free cholesterol and [3H]cholesteryl oleoyl ether suggest that hepatic lipase enhances the incorporation of HDL-esterified cholesterol. However, the amount of free cholesterol delivered as a result of treatment with hepatic lipase was 4-fold that of esterified cholesterol. On the basis of HDL composition, the cellular incorporation of free cholesterol was about 10 times that which would occur by the uptake and degradation of intact particles. The preferential incorporation of HDL-free cholesterol did not require the presence of lysophosphatidylcholine. To correlate the events observed at the cellular level with alterations in lipoprotein structure, high-resolution, proton-decoupled 13C nuclear magnetic resonance spectroscopy (90.55 MHz) was performed on HDL3 in which the cholesterol molecules were replaced with [4-13C]cholesterol by particle reconstitution.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of the hepatic lipase induced accumulation of high-density lipoprotein cholesterol by cells in culture. 389 72


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