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)

Valine-depleted amino acid imbalance, while having a suppressive effect on tumor growth, may induce fatty liver. We administered valine-depleted total parenteral nutrition (TPN) solution to rats subcutaneously transplanted with ascites containing hepatoma AH-109A and examined the time course of the development of fatty liver. An accumulation of fatty vacuoles was observed in hepatocytes on day 4. To prevent the development of fatty liver in tumor-bearing rats, we administered a small amount of valine in addition to the valine-depleted imbalance solution via the central vein. Such treatment, however, resulted in neither the prevention of fatty liver development nor the suppression of tumor growth. To supply valine to the liver, we administered a low concentration of valine via the portal vein simultaneously with central venous administration of valine-depleted TPN solution. As a result, the peripheral blood valine level of these rats was < 0.5 that of the control group, but the valine in the liver was maintained at the same level as that of the control group, and accumulation of triacylglycerols in the liver was slight. However, the suppressive effect on tumor growth was maintained, as the tumor weight was suppressed to almost the same degree as that of rats administered only the valine-depleted solution.
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PMID:Effect of valine-depleted total parenteral nutrition on fatty liver development in tumor-bearing rats. 958 71

We examined the inhibitional and nutritional effects of total parenteral nutrition (TPN) containing D-amino acids (D-phenylalanine, D-Phe; D-valine, D-Val; D-leucine, D-Leu; D-methionine, D-Met) on tumor growth in AH109A hepatoma-bearing rats. Five experimental groups were examined: a control amino acid solution group (control group), D-Phe group, D-Val group, D-Leu group and D-Met group. The analysis of tumor volume and weight revealed significant tumor growth inhibition in the D-Val group as compared with the control group. In the D-Val group, decreases of DNA and protein contents in the tumor tissues were also observed. The D-Leu and D-Met groups showed a tendency toward tumor growth inhibition. The protein content in the liver tissues of these two groups was significantly higher as compared with the control group. The DNA content in the liver tissue was also significantly higher in the D-Met group. The body weight including the tumor (on the final day of TPN) was significantly lower in the D-Val group as compared with the control group, but there was no significant difference in the groups for body weights not including tumors (carcass body weight). The hematocrit and hemoglobin values, indicators of anemia, were significantly higher in the D-Val group as compared with the control group. From these results, regarding tumor growth inhibition, the D-Val solution had the strongest inhibitory effect with no negative influence on the host, and improvement of nutritional status was also suggested in the rats that received the D-Leu or D-Met solutions.
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PMID:Tumor growth inhibition and nutritional effect of D-amino acid solution in AH109A hepatoma-bearing rats. 959 Dec 36

Cirrhosis and hepatocellular carcinoma occur as long-term complications of chronic hepatitis B virus (HBV) infection. Antiviral therapy is potentially a successful approach for the treatment of patients with HBV infection, which includes the nucleoside analog, lamivudine [(-)2'-deoxy-3'-thiacytidine, 3TC]. Although resistance to lamivudine therapy has been reported in several HBV-infected patients, the pattern of resistance-associated mutations in HBV has not been fully characterized. We report a DNA sequence database that includes a 500-base pair region of the HBV polymerase gene from 20 patients with clinical manifestations of lamivudine resistance. Analysis of the database reveals two patterns of amino acid substitutions in the tyrosine, methionine, aspartate, aspartate (YMDD) nucleotide-binding locus of the HBV polymerase. HBV DNA from the sera of patients in Group I exhibits a substitution of valine for methionine at residue 552, accompanied by a substitution of methionine for leucine at residue 528. Patients in Group II had only an isoleucine-for-methionine substitution at position 552. Reconstruction of these mutations in an HBV replication-competent plasmid was performed in a transient transfection cell assay to determine the function/relevance of these mutations to lamivudine resistance. Both Group I and Group II mutations resulted in a substantial decrease in sensitivity to lamivudine treatment (> 10,000-fold shift in IC50 over wild-type [wt] IC50), strongly indicating that these mutations were involved in resistance to lamivudine. A hypothetical model of the HBV reverse transcriptase has been generated for further study of the role of these mutations in lamivudine resistance.
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PMID:Identification and characterization of mutations in hepatitis B virus resistant to lamivudine. Lamivudine Clinical Investigation Group. 962 Mar 41

Familiar Amyloid Polyneuropathy (FAP), an autosomal dominant inherited multisystemic disorder was first observed by Corino de Andrade, a Portuguese neurologist, in 1939. This disease of Portuguese origin was probably spread by fishermen, mainly to Sweden and Japan. It is characterized by a progressive peripheral polyneuropathy and autonomic neuropathy (erectile sexual disfunction, gastrointestinal disfunction, bladder dysfunction and cardio vascular disease) and malnutrition. There are neural and systemic amiloid deposits. Type I FAP, of Portuguese origin, is the most common variety. The amyloid protein is the variant transthyretin (TTR) in which methionine (MET) is a substitute for valine in position 30 (TTR MET 30). It is mainly produced by the liver (90%) and, in small amounts, by the choroidal plexus. Symptoms usually start in the 3rd and 4th decade of life and the patients usually die within 10-15 years. From the therapeutic options--plasmapheresis, immunoadsorption and liver transplantation; the latter seems to be the only one, which stops the production of TTR MET 30 in a permanent way, by means of the liver. The lack of any other effective therapy and the success of the first liver transplantation performed in Sweden arouse great hope. So far, around 300 patients have been transplanted all over the world. A hundred and thirty of them were transplanted in Portugal. A Kaplan Meier survival curve of the Portuguese patients shows a survival rate of 78% at 5 years. However, in spite of the progression of the disease being halted, the irreversibility of some neurological lesions seems to persist. This fact raises the problem of the timing of the transplantation. It seems that the patients should be transplanted as soon as the symptoms start, since mortality and severe morbidity seems to mainly involve those in whom symptomatic disease has lasted longer than six years. As the explanted liver is a morphologic normal liver, a sequential (domino) transplant has been carried out in 16 cases so far done--by one of the authors (ALF) on patients with either hepatocellular carcinoma or liver metastatic disease.
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PMID:Liver transplantation for familial amyloid polyneuropathy. 984 68

The enantioselectivity of 4-hydroxylation of bunitrolol (BTL), a beta-adrenoceptor blocking drug, was studied in microsomes from human liver, human hepatoma (Hep G2) cells expressing CYP2D6, and lymphoblastoid cells expressing CYP2D6. Kinetics in human liver microsomes showed that the Vmax value for (+)-BTL was 2.1-fold that of (-)-BTL, and that the Km value for (+)-BTL was lower than that for the (-)-antipode, resulting in the intrinsic clearance (Vmax/Km) of (+)-BTL being 2.1-fold over its (-)-antipode. CYP2D6 (CYP2D6-met) expressed in Hep G2 cells had a methionine residue at position 373 of the amino acid sequence and a rat-type N-terminal peptide (MELLNGTGLWSM) instead of the human-type (MGLEALVPLAVIV), and showed enantioselectivity of [(+)-BTL < (-)-BTL] for the rate of BTL 4-hydroxylation. In contrast, enantioselectivity [(+)-BTL > (-)-BTL] for Hep G2-CYP2D6 (CYP2D6-val) with a human-type N-terminal peptide that had a valine residue at 374, which corresponds to the methionine of the CYP2D6-met variant, was the same as that for human liver microsomes. We further confirmed that CYP2D6-met and CYP2D6-val expressed in human lymphoblastoid cells, both of which have methionine and valine, respectively, at position 374 and a human-type N-terminal peptide, exhibited the same enantioselectivities as those obtained from CYP2D6-met and CYP2D6-val expressed in the Hep G2 cell system. These results indicate that the amino acid at 374 of CYP2D6 is one of the key factors influencing the enantioselectivity of BTL 4-hydroxylation.
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PMID:Enantioselectivity of bunitrolol 4-hydroxylation is reversed by the change of an amino acid residue from valine to methionine at position 374 of cytochrome P450-2D6. 991 47

Recently, lamivudine used to treat patients with hepatitis B virus (HBV) infection was revealed to have potent antiviral activity. However, HBV resistance to lamivudine has been reported and shown to have amino acid substitutions in the methionine residue of the conserved tyrosine (Y), methionine (M), aspartate (D), aspartate (D) motif of RNA-dependent DNA polymerase. To explore the consequences of substitutions in this motif (YMDD), we made 7 variants by substituting the methionine of the YMDD motif with isoleucine (I), valine (V), alanine (A), leucine (L), lysine (K), arginine (R), and threonine (T). Replication ability of these variants was evaluated by transfection into human hepatoma cells. Sensitivity to lamivudine was tested for replication-competent variants. Four variants with hydrophobic substitutions (I, V, A, and L) remained replication-competent, whereas 3 others with hydrophilic substitutions (K, R, and T) exhibited impaired replication. Of the 4 replication-competent variants, 2 (I and V) were resistant, and 2 (A and L) were sensitive to lamivudine. Because the polymerase and the surface gene overlap, the introduction of these mutations affected the secretion of hepatitis B surface antigen (HBsAg), namely 4 variants (I, V, L, and R) secreted HBsAg, whereas 3 variants (A, K, and T) did not. Our study elucidated that only one amino acid substitution in the YMDD motif was sufficient to cause lamivudine resistance in vitro. As a result of replication competence and lamivudine sensitivity, only viruses having YIDD or YVDD sequences may appear during treatment with lamivudine. This in vitro system could be used to study HBV mutations, replication competence, and their susceptibility to antivirals.
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PMID:YMDD motif in hepatitis B virus DNA polymerase influences on replication and lamivudine resistance: A study by in vitro full-length viral DNA transfection. 1005 1

Mechanisms of methylmercury (MeHg) and inorganic mercury (Hg) uptake were examined in HepG2 cells, a human hepatoma-derived cell line. MeHg uptake was faster when it was present as the l-cysteine complex, as compared to the glutathione (GSH), CysGly, gamma-GluCys, d-cysteine, N-acetylcysteine, l-penicillamine, or albumin complexes. Uptake of MeHg-l-cysteine was independent of Na(+), stereoselective, and was inhibited by the amino acid transport system l substrates l-leucine, l-valine, and l-phenylalanine (5 mM). Moreover, [(3)H]l-leucine uptake was inhibited by MeHg-l-cysteine, suggesting that MeHg-l-cysteine is transported into HepG2 cells by an l-type amino acid carrier. Uptake of MeHg as the GSH complex (MeHg-SG) was dependent on the extracellular GSH concentration, and was diminished when cellular gamma-glutamyl transpeptidase activity was inhibited. Inorganic mercury uptake was slower than that of MeHg, but was also sensitive to the type of thiol ligand present. These findings demonstrate that mercury uptake by HepG2 cells is dependent on the chemical structure of the mercury compound, the thiol ligand, and the activity of gamma-glutamyl transpeptidase. gamma-Glutamyl transpeptidase appears to play a key role in the disposition of MeHg-SG by facilitating the formation of MeHg-l-cysteine, which is readily transported into the cells on an amino acid-type carrier.
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PMID:gamma-Glutamyl transpeptidase and l-cysteine regulate methylmercury uptake by HepG2 cells, a human hepatoma cell line. 1100 Jan 2

An A-->T substitution in cDNA nucleotide 1197 (c.1197A/T) of the human phenylalanine hydroxylase (PAH) gene has been regarded as a silent mutation, because both the wild-type (GUA) and the mutant (GUU) alleles encode a valine residue at codon 399 (V399 V). The nucleotide c.1197 is located at the 3'-end of exon 11at position -3 of the exon-intron junction. To explore whether the substitution exerts any effects on the processing of the PAH mRNA, illegitimate PAH transcripts from lymphoblast cultures of a phenylketonuria (PKU) patient heterozygous for c.1197A/T were analyzed by the polymerase chain reaction following reverse-transcription (RT-PCR). mRNAs with an exon 11 deletion were revealed. Furthermore, by using an R408 W mutation in the paternal allele as a marker, sequence analysis of the RT-PCR products indicates that virtually all PAH transcripts from the maternal allele with the c. 1197A/T substitution do not contain exon 11. To address whether this substitution is the main determinant for exon skipping, PAH minigenes with or without the substitution were constructed and transfected to a human hepatoma cell line. Analysis of the transcription products by S1 nuclease mapping clearly indicated that such exon 11 skipping was directly associated with the c.1197A/T substitution. Thus, this study demonstrates that the c.1197A/T substitution in the PAH gene is not just a neutral polymorphism but a mutation that induces post-transcriptional skipping of exon 11 leading to a PKU phenotype.
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PMID:A silent mutation induces exon skipping in the phenylalanine hydroxylase gene in phenylketonuria. 1121 2

Mutated constituents of the DNA replication complex might contribute to the mutational load of the genome during tumor development by impairing DNA synthesis as well as cell cycle-related control of DNA replication. To prove or disprove this hypothesis, we looked for mutations in the cDNA sequences of the four subunits of DNA polymerase alpha-primase from both highly malignant Novikoff hepatoma cells and regenerating normal rat liver and compared physicochemical and catalytic properties of the DNA polymerase alpha-primase complexes purified from both sources. Sequence analysis showed two mutations in subunit B from Novikoff cells: one in nucleotide position 855 (CCG-->CCA) that did not result in an amino acid exchange and one in position 862 (GTG-->ATG) that caused a change of valine to methionine in codon 288. No mutation was found in the three other subunits. The wild-type and mutated sequences of subunit B were cloned and expressed in vitro. Sedimentation analysis of the expressed polypeptides revealed different sedimentation constants, indicating that the amino acid exchange affected the conformation of subunit B. The analysis of the purified DNA polymerase alpha-primase complexes showed a sedimentation value that was significantly higher for the enzyme complex from normal liver than for that from Novikoff cells. In addition, DNA polymerase alpha-primase complexes from Novikoff cells showed higher sensitivity to camptothecin, topotecan, and structurally related compounds (such as (R,S)-7-ethyl-10-hydroxy camptothecin, 9-aminocamptothecin, and 10-hydroxycamptothecin) than the enzyme from normal rat liver. Thus, the amino acid change found in subunit B appears to result in a conformational change of the DNA polymerase alpha-primase complex from Novikoff hepatoma cells. Whether this mutation influences genetic instability or tumor development needs to be explored.
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PMID:A mutation in subunit B of the DNA polymerase alpha-primase complex from Novikoff hepatoma cells concomitant with a conformational change and abnormal catalytic properties of the DNA polymerase alpha-primase complex. 1153 67

A cDNA that encodes a novel Na+-independent neutral amino acid transporter was isolated from FLC4 human hepatocarcinoma cells by expression cloning. When expressed in Xenopus oocytes, the encoded protein designated LAT3 (L-type amino acid transporter 3) transported neutral amino acids such as l-leucine, l-isoleucine, l-valine, and l-phenylalanine. The LAT3-mediated transport was Na+-independent and inhibited by 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, consistent with the properties of system L. Distinct from already known system L transporters LAT1 and LAT2, which form heterodimeric complex with 4F2 heavy chain, LAT3 was functional by itself in Xenopus oocytes. The deduced amino acid sequence of LAT3 was identical to the gene product of POV1 reported as a prostate cancer-up-regulated gene whose function was not determined, whereas it did not exhibit significant similarity to already identified transporters. The Eadie-Hofstee plots of LAT3-mediated transport were curvilinear, whereas the low affinity component is predominant at physiological plasma amino acid concentration. In addition to amino acid substrates, LAT3 recognized amino acid alcohols. The transport of l-leucine was electroneutral and mediated by a facilitated diffusion. In contrast, l-leucinol, l-valinol, and l-phenylalaninol, which have a net positive charge induced inward currents under voltage clamp, suggesting these compounds are transported by LAT3. LAT3-mediated transport was inhibited by the pretreatment with N-ethylmaleimide, consistent with the property of system L2 originally characterized in hepatocyte primary culture. Based on the substrate selectivity, affinity, and N-ethylmaleimide sensitivity, LAT3 is proposed to be a transporter subserving system L2. LAT3 should denote a new family of organic solute transporters.
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PMID:Identification of a novel system L amino acid transporter structurally distinct from heterodimeric amino acid transporters. 1293 Aug 36


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