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)

Teleocidin, a phorbol ester-type tumor promoter, enhanced actin redistribution, vacuole formation and c-fos expression of PLC/PRF/5 hepatoma cells. This tumor promoter also inhibited calcium mobilization induced by epidermal growth factor (EGF). Thapsigargin, a specific inhibitor of endoplasmic reticulum Ca(2+)-ATPase, elevated cytosolic calcium, enhanced c-fos expression and antagonized the vacuole formation induced by teleocidin without interfering with actin redistribution and Lucifer yellow uptake. On the other hand, a calcium ionophore ionomycin elevated both cytosolic Ca2+ and c-fos mRNA but could not antagonize the vacuole formation induced by teleocidin. From these results it was speculated that the Ca2+ leak from the endoplasmic reticulum rather than the elevation of cytosolic Ca2+ appeared to be responsible for the specific inhibition of vacuole formation by thapsigargin.
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PMID:Thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase, enhances c-fos expression but antagonizes vacuole formation of human hepatoma cells induced by teleocidin. 848 67

1. This study was designed to determine the role of sodium-potassium adenosine triphosphatase (Na(+)-K(+)-ATPase) in the regulation of human corpus cavernosum smooth muscle contractility by nitric oxide (NO). In addition, we determined if the modulation of Na(+)-K(+)-ATPase activity by NO is dependent on the increase in intracellular cyclic GMP concentration. 2. The effect of NO donors, sodium-nitroprusside (SNP) and S-nitroso-glutathione (S-NO-Glu), and a permeable cyclic GMP analogue, 8-bromo-cyclic GMP, on Na(+)-K(+)-ATPase activity (measured as ouabain-sensitive 86Rb-uptake) was studied in human cultured corpus cavernosum smooth muscle cells (HCCSMC). In addition, the effect of the cyclic GMP lowering agent, methylene blue, on NO-induced increase in Na(+)-K(+)-ATPase activity was studied. 3. SNP (1 microM) caused time-dependent increases in ouabain-sensitive Rb-uptake (33-72%) over 2-20 min in HCCSMC. The stimulation of ouabain-sensitive Rb-uptake by SNP was concentration-dependent (30 and 102% with 0.1 and 1 microM SNP, respectively). Similarly, significant increases in ouabain-sensitive Rb-uptake were obtained with 1 and 10 microM S-NO-Glu. In contrast, incubation of HCCSMC with 8-bromo-cyclic GMP (100 microM) did not increase ouabain-sensitive Rb-uptake. 4. S-NO-Glu induced-increase in intracellular cyclic GMP synthesis, but not the increase in ouabain-sensitive Rb-uptake, was completely inhibited by methylene blue in HCCSMC. 5. The Na(+)-K(+)-ATPase inhibitor, ouabain, caused a concentration-dependent increase in tension (0.5 to 2 fold) in tissues contracted with 15 mM KCl. SNP and S-NO-Glu caused a concentration-dependent relaxation (concentration required to cause half maximal relaxation (ED50) = 0.04 and 0.2 microM, respectively) of HCC strips contracted with 15 mM K+. Ouabain (0.1 to 10 microM) inhibited the response to SNP and S-NO-Glu by shifting the concentration-response curves to the right and preventing full smooth muscle relaxation.6. These results indicate that the activity of Na+-K+-ATPase modulates the contractility of HCC smooth muscle, and that NO stimulates Na+-K+-ATPase activity in HCCSMC independently of its ability to increase the intracellular cyclic GMP concentration. They also suggest that stimulation of Na+-K+-ATPase activity plays an important role in NO-induced relaxation of HCC smooth muscle
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PMID:Possible role of Na(+)-K(+)-ATPase in the regulation of human corpus cavernosum smooth muscle contractility by nitric oxide. 856 49

DNA polymerases alpha, delta and epsilon from normal regenerating rat liver and Novikoff hepatoma cells were purified about 300-fold, characterized, and checked for sensitivity towards drugs known to inhibit cell proliferation. Characterization included (a) identification of associated proteins, (b) measurement of physiochemical constants (including sedimentation coefficients, diffusion coefficients, calculation of relative molecular masses), (c) quantification of catalytic activities using specific DNA primer templates (Km values) and specific inhibitors (Ki values), and (d) discrimination between DNA polymerases from normal cells and those from malignant cells using inhibitors of cell proliferation. (a) DNA primase associated with DNA polymerase alpha, and 3'-5' exonuclease accompanying DNA polymerases delta and epsilon had similar activities. (b) Comparison of physicochemical and catalytic properties of DNA polymerases from both sources revealed similarities but also some important differences. Sedimentation and diffusion coefficients of DNA polymerases alpha and epsilon from malignant cells differed significantly. (c) The DNA-binding domain of DNA polymerases alpha and epsilon from hepatoma cells was altered since Km values, determined with several specific DNA primer-templates, were higher. Furthermore, dNTP-binding sites of DNA polymerases from malignant cells, when probed with specific inhibitors (aphidicolin, butylphenyl-dGTP, carbonyldiphosphonate, and dideoxy-TTP) showed significantly lower Ki values, indicating lower affinity to deoxyribonucleoside 5'-triphosphates. (d) Sixteen drugs representative of various modes of interaction with DNA and protein were chosen. Dose/response experiments were performed and the concentration at which the polymerizing activity was reduced to 50% was calculated (K50 values). Preferential inhibition of DNA polymerases alpha, delta, and epsilon from Novikoff hepatoma cells was found for: the intercalating drugs doxorubicin, daunorubicin, amsacrine, mitoxantrone, quinacrine and ethidium bromide, the minor-groove binders distamycin and netropsin, the ATPase-blocking agents novobiocin and coumamycin, and the topoisomerase I inhibitors camptothecin and topotecan. When the sensitivity of polymerases delta and epsilon was measured using poly(dA.dT) as a primer-template, the preferential inhibition of the enzymes from malignant cells was even more pronounced. Drugs known to trap the DNA-topoisomerase-II complex, etoposide, nalidixic acid, teniposide, and merbarone did not affect DNA polymerases irrespective of the source. Since the majority of the inhibitors used, particularly intercalators and minor-groove binders, act by modification of the primer-template, inhibition of DNA synthesis must have occurred through weakening of non-covalent bonds between DNA and catalytic polypeptides. Consequently, preferential inhibition of DNA polymerases from malignant cells seems to be indicative of abnormally diminished binding of the enzymes to their primer-templates. This effect may be caused by conformational alterations in polymerases from malignant cells which affect the DNA binding domains. Similarly, changes in physicochemical and kinetic constants are indicative of alterations of dNTP-binding domains.
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PMID:Preferential inhibition of DNA polymerases alpha, delta, and epsilon from Novikoff hepatoma cells by inhibitors of cell proliferation. 857 84

Plasma membrane P-glycoprotein is known as an ATP-dependent drug efflux pump that confers multidrug resistance to tumor cells. None of the reported purification procedures worked properly for our P-glycoprotein-overproducing cell lines, i.e. murine lymphoid leukemia P388/ADR25, rat hepatoma AS30-D/COL10, and human lymphoblastic leukemia CEM/VLB5 cells. We have thus developed a general procedure for efficient purification of P-glycoprotein by combining solubilization with sodium dodecyl sulfate and chromatography on ceramic hydroxyapatite. This procedure was successful for the three cell lines and yielded 70% of the P-glycoprotein present in the starting plasma membranes with more than 99% purity. After exchanging sodium dodecyl sulfate into dodecyl maltoside and reconstitution into liposomes, purified P-glycoprotein exhibited a specific ATPase activity of about 200 nmol/min/mg, which was very similar to that obtained for P-glycoprotein solubilized and purified with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid. This ATPase activity was sensitive to orthovanadate inhibition and stimulated by verapamil and other drugs. More importantly, drug transport properties of the reconstituted P-glycoprotein were comparable with those of P-glycoprotein embedded in plasma membranes. Since it is virtually devoid of lipids, this preparation is suitable for both functional and structural investigations.
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PMID:Efficient purification and reconstitution of P-glycoprotein for functional and structural studies. 891 May 34

L-Asparagine stimulates bi-directional Ca(2+) flows and induces ornithine decarboxylase in Reuber H-35 hepatoma cells. Previously it has been shown that these effects are completely, but reversibly inhibited by lanthanum chloride. In this study we examined the role(s) of Ca(2+) flows using more specific Ca(2+) flow inhibitors. It was shown that ornithine decarboxylase induction was inhibited by CdCl(2) and verapamil at concentrations above 1 mu M and 100 mu M respectively, but was unaffected by as much as 300 mu M NiCl(2), 1 mM nifedipine, or 10 mu M omega-conotoxin. Enzyme induction was blocked by the Ca(2+)-ATPase pump antagonists vanadate and Compound 48/80 in a dose-dependent manner. These results, taken together with the observations that extracellular Ca(2+) is essential for enzyme induction but a substantial elevation of cytoplasmic [Ca(2+)] is not, suggest that Ca(2+) inflow independent of the receptor-activated Ca(2+) channels, and the Ca(2+)-ATPase mediated Ca(2+) out-flow, are both important factors in the action of L-asparagine.
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PMID:Characterization of Ca(2+) flows essential in ornithine decarboxylase induction by L-asparagine in rat hepatoma cells using Ca(2+) flow inhibitors. 913 51

Cancer cells, despite growing aerobically, have the propension to utilize the glycolytic pathway as energy source. This biochemical phenotype is accompanied by a decreased content of mitochondria and, paradoxically, by enhanced transcription of nuclear and mitochondrial-encoded genes for the enzymes of oxidative phosphorylation (OXPHOS). The role of OXPHOS enzymes in normal and neoplastic cell growth has been studied in liver regeneration and human hepatocellular carcinoma. In early liver regeneration characterized by active mtDNA replication, a decrease in the content and activity of ATP synthase occurs while transcription of the ATPsyn beta nuclear gene is activated. Translation of ATP synthase subunits seems, on the contrary, to be less effective in this phase. In the second replicative phase of liver regeneration, the repression of ATPsyn beta translation is relieved and normal cell growth starts. In this replicative phase the recovery of the liver mass appears to be directly related to the recovery of the OXPHOS capacity. Mitochondria isolated from biopsies of human hepatocellular carcinoma exhibit a decreased rate of respiratory ATP synthesis (OXPHOS) and a decreased ATPase activity. The decline in the activity of the ATP synthase is found to be associated with a decreased content of the ATPsyn beta in the inner mitochondrial membrane. In neoplastic tissue the ATPase inhibitor protein (IF1) is overexpressed. This could contribute to prevent hydrolysis of glycolytic ATP in cancer cells. A peptide segment of IF1 (IF1-(42-58)-peptide), constructed by chemical synthesis, proved to be equally effective as IF1 in inhibiting the ATPase activity of the ATP synthase complex in the mitochondrial membrane deprived of IF1. The synthetic peptide might turn out to be a useful tool to develop immunological approaches for the control of neoplastic growth.
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PMID:Oxidative phosphorylation enzymes in normal and neoplastic cell growth. 938 98

P-gp (Pgp) is a cell surface ATPase which confers resistance to many of the most active chemotherapy drugs, including taxol, doxorubicin, and vinca alkaloids. Pgp can be detected in human cancers by immunohistochemistry, RNA probes, or by functional assays utilizing transported fluorescent dyes such as rhodamine. The expression of Pgp in untreated human cancers is highly variable, being almost universal in colon, hepatocellular carcinoma, and renal cell cancers, less common in breast, ovarian, and lymphoid malignancies. At least part of the heterogeneity is attributable to different definitions of positivity even with a given method of detection. In chemotherapy naive cancers, resistant cells may not occur very frequently. Whilst the Goldie-Coldman hypothesis predicts treatment failure if 1 cell in 10(6) expresses a resistance mechanism, no method of detection yet described can reliably achieve this. The field has reached a stage in which it may be possible to detect Pgp accurately in advanced cancers which have failed chemotherapy allowing phase II clinical trials to be performed in Pgp-positive tumors. In terms of which Pgp inhibitors are selected for clinical study it is likely that selection of Pgp inhibitors with nM potency to bind to Pgp will be important. Such drugs should undergo extensive phase I trial evaluation to assess pharmacokinetic interactions with a range of cytotoxic drugs before entering randomized trials. In randomized clinical trials Pgp detection may be less important, as disease-free survival and overall survival would be the key end-points, but the Pgp positivity of relapsed disease would indicate if treatment with inhibitors of Pgp-eliminated Pgp-expressing clones. The accurate detection of Pgp in human cancers is being refined and will be an essential component of future Pgp inhibitor clinical trials. Finally, these trails must be of sufficient size (> 500 patients per arm) to reliably detect clinically meaningful differences.
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PMID:Testing the role of P-glycoprotein expression in clinical trials: applying pharmacological principles and best methods for detection together with good clinical trials methodology. 947 46

Composition and amount of 45Ca2+-binding proteins in the inner membrane fraction of rat liver and Zajdela hepatoma mitochondria were determined. In the inner membrane of liver mitochondria, three major 45Ca2+-binding polypeptides: a protein of approximately 130 kDa (carbamoyl-phosphate synthetase), a glycoprotein of 43-44 kDa (previously considered as the calcium uniporter), and 29-30 kDa protein were found. These components were absent (130 kDa component) or relatively reduced (43-44 kDa and 29-30 kDa components) in the inner membrane of hepatoma mitochondria. Previously unknown low molecular mass polypeptides, having very high Ca2+-binding ability, were found in the inner membrane of hepatoma mitochondria. One of them might be the natural Ca2+-binding inhibitor of H+-ATPase.
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PMID:Calcium binding to polypeptides of rat liver and Zajdela hepatoma mitochondrial inner membranes. 950 39

We studied the effects of bafilomycin A1, a potent and specific inhibitor of vacuolar H+ ATPase (V-ATPase), on the process of autophagy in rat hepatoma cell line, H-4-II-E cells. To induce autophagy, cells were transferred from Dulbecco's modified Eagle medium containing 12% fetal calf serum into Hanks' balanced salt solution. When bafilomycin A1 was added to Hanks' balanced salt solution, endogenous protein degradation was strongly inhibited and numerous autophagosomes accumulated in H-4-II-E cells, whereas autolysosomes decreased in number. Acid phosphatase activity was not detected in the autophagosomes which accumulated in the presence of bafilomycin A1, suggesting that fusion between autophagosomes and lysosomes was disturbed by this drug. Inhibition of the fusion was reversible, and the autophagosomes changed into autolysosomes after the removal of the inhibitor. Bafilomycin A1 also prevented the appearance of endocytosed HRP in autophagic vacuoles. These results suggested that acidification of the lumenal space of autophagosomes or lysosomes by V-ATPase is important for the fusion between autophagosomes and lysosomes.
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PMID:Bafilomycin A1 prevents maturation of autophagic vacuoles by inhibiting fusion between autophagosomes and lysosomes in rat hepatoma cell line, H-4-II-E cells. 963 28

The polarized rat hepatoma/human fibroblast hybrid cell line, WIF-B, forms apical vacuoles into which cholephilic substances are secreted. We studied expression, localization, and function of the apical conjugate export pump, Mrp2, in WIF-B cells. Mrp2, the apical isoform of the multidrug resistance protein, alternatively termed canalicular Mrp (cMrp) or canalicular multispecific organic anion transporter (cMoat), is a 190-kd membrane glycoprotein mediating adenosine triphosphate (ATP)-dependent transport of glucuronides, glutathione S-conjugates, and other amphiphilic anions across the hepatocyte canalicular membrane into bile. Expression of the rat mrp2 gene in WIF-B cells was shown by reverse-transcription polymerase chain reaction (PCR), followed by sequencing of the amplified 789-bp fragment. Immunoblotting, using antibodies reacting with the amino-terminal or with the carboxyl-terminal sequence of rat Mrp2, detected the 190-kd glycoprotein in WIF-B cell homogenates. Immunofluorescence microscopy localized Mrp2 to the apical membrane domain. Preloading of WIF-B cells with a membrane-permeable ester of the calcium-dependent fluorescent indicator, Fluo-3, was followed by Mrp2-mediated secretion of the amphiphilic anion, Fluo-3, into the apical vacuoles. This transport was potently inhibited by cyclosporin A added to the culture medium. Direct measurements of ATP-dependent transport into Mrp2-containing plasma membrane vesicles in comparison with Mrp2-deficient vesicles established that Fluo-3 is transported by Mrp2 with a Km value of 3.7 micromol/L. Our results indicate that the polarized WIF-B cells express the rat ortholog of the apical conjugate-transporting ATPase, Mrp2. The function of Mrp2 as well as the action of inhibitors can thus be analyzed by use of the fluorescent amphiphilic anion, Fluo-3.
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PMID:Expression of the apical conjugate export pump, Mrp2, in the polarized hepatoma cell line, WIF-B. 979 19


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