Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N1-S1/FdUrd Novikoff hepatoma cells, which lack thymidine kinase activity, are resistant to 5-fluorouracil (FUra) as well as 5-fluorodeoxyuridine (FdUrd), suggesting that the pathway, FUra leads to FdUrd leads to FdUMP, is utilized for the conversion of FUra to FdUMP. However, the inhibition of thymidylate synthetase activity, the presumed target of FdUMP, by 1 X 10(-4) M FUra in intact N1-S1 Novikoff hepatoma cells, which have significant levels of thymidine kinase activity, is completely eliminated by 5 X 10(-4) M hydroxyurea, which is a potent inhibitor of ribonucleotide reductase. These results imply that the formation of ribonucleotides and does not involve thymidine kinase. This apparent dichotomy can be explained by the fact that, in addition to the well known lack of thymidine kinase activity, [14C]FUra conversion to ribonucleotides is greatly depressed in the N1-S1/FdUrd cells. Hence, the formation of FdUMP from FUra in Novikoff hepatoma cells apparently proceeds primarily via the intermediate formation of ribonucleotides. The decreased conversion of FUra to ribonucleotides in N1-S1/FdUrd cells decreases not only the ability of the analog to inhibit DNA synthesis, but also its effect on RNA metabolism. FUra, at a concentration of 1 X 10(-5) M, inhibits rRNA maturation in N1-S1 cells, but not in N1-S1/FdUrd cells. Since N1-S1/FdUrd cells are completely resistant to 1 X 10(-5) M FUra, whereas N1-S1 cells are completely inhibited by 1 X 10(-5) M FUra, even in the presence of 1 X 10(-4) M thymidine, the effects of FUra on RNA metabolism appear to contribute significantly to the cytotoxicity of the analog at higher drug concentrations.
 ...
PMID:Metabolism of 5-fluorouracil in sensitive and resistant Novikoff hepatoma cells. 19 Feb 17

Fractions of heavy and light mitochondria are isolated from homogenates of homologous rat tissues (intact liver, regenerating liver within 24 hours after hepatectomy and 27 hepatoma) by means of differential centrifugation. It is found that tumour mitochondria have higher heterogeneity and lower buyoant density than mitochondria from normal hepatocytes. The activity of two enzymes of DNA precursors synthesis (ribonucleotide reductase and thymidine kinase) in subcellular fractions is demonstrated to correlate with the tissue growth rate. A single injection of cyclic AMP into hepatectomised rats resulted in the retardation of the regeneration process, and the activity of both enzymes reached its normal level in all the fractions studied after 24 hours after the operation. Thymidine kinase and ribonucleotide reductase are located mainly in the mitochondrial matrix, however, pronounced enzyme activity is observed also in membrane fractions. The activity of the enzymes in the fraction of external mitochondria membranes in rapidly growing tissues is 2--3 times as high as in the same fraction from normal rat liver.
 ...
PMID:[Mitochondrial thymidine kinase and ribonucleotide reductase from rat liver and rat hepatoma 27]. 19 36

Inosine dialdehyde (INOX), the periodate oxidation product of inosine, inhibited the proliferation of various tumor cell lines in suspension culture in a concentration-dependent manner. A concentration of about 1 mM was required to completely inhibit the proliferation of Novikoff rat hepatoma and mouse L-cells, whereas about 0.1 mM completely inhibited the proliferation of L1210 and P388 mouse leukemia and Chinese hamster ovary cells. INOX inhibited in a similar time- and concentration-dependent manner the synthesis of protein, RNA, and DNA, as measured by the incorporation of labeled amino acid, uridine, and thymidine, into acid-insoluble material, without significantly affecting the incorporation of these precursors into the acid-soluble pool. Flow microfluorometric analyses showed that many of the INOX-treated cells became arrested in G2 + M. The results are consistent with the view that INOX affects multiple metabolic steps. The effects of INOX were quite different from those caused by typical inhibitors of ribonucleotide reductase, hydroxyurea, and 2,3-dihydro-1H-pyrazolo(2,3-a)imidazole, which very rapidly inhibited DNA synthesis and caused arrest of the cells in G1, with minimal effects on RNA and protein synthesis.
 ...
PMID:Mechanism of action of inosine dialdehyde (NSC 118994) in the inhibition of proliferation of tumor cells in culture. 19 37

Epitope-specific antibodies to the M1 and M2 subunits of mammalian ribonucleotide reductase were prepared using peptides predicted to have a high antigenic index. Western blotting demonstrated that the anti-M1 antibody was specific for the 89-kilodalton M1 subunit (and its degradation fragments) and the anti-M2 antibody specifically recognized the 45-kilodalton M2 subunit. Both antibodies inhibited the CDP-reductase activity of the holoenzyme. Using these antibodies, both the M1 and M2 subunits were shown to be localized in the cytoplasm and in the nuclear regions of a number of cell types, including B77 avian sarcoma virus transformed NRK cells, T51B rat liver cells, 5123tc hepatoma cells, and rat liver cells in vivo. In addition, the M1 subunit was found to be localized as a halo around isolated rat liver nuclei. Biochemical analysis of the cytoplasmic fraction of liver cells and a Triton X-100 wash of nuclei from these cells confirmed the location of the enzyme activity in these cellular compartments. The M1 subunit appears to be glycosylated, as indicated by its retention on a Affi-Gel-concanavalin A affinity column. Therefore, in mammalian cells ribonucleotide reductase appears to be not only in the cytoplasm, but is also associated with the nuclear membrane or nuclear lamina. The activity of the enzyme in the membrane fraction changes dynamically during the cell cycle.
 ...
PMID:Evidence that mammalian ribonucleotide reductase is a nuclear membrane associated glycoprotein. 220 48

Although they are proliferatively quiescent, the cells in the intact adult rat liver express the gene coding for the M1 subunit of ribonucleotide reductase. But since they do not need deoxyribonucleotides, they promptly inactivate the 88 to 90 kDa M1 products and degrade them into 40 kDa fragments. Partial hepatectomy signals the remaining cells to start proliferating. Two hours before the onset of DNA replication, around 16 to 18 hr after partial hepatectomy, the cells start accumulating a large pool of functional ribonucleotide reductase M2 subunits. Near the end of the G1 build-up the cells step up M1 gene expression, stop inactivating, and reduce the degradation of the M1 products. The accumulating functional 88 to 90 kDa M1 subunits, each with more than one catalytic site, couple with functional M2 subunits to produce active ribonucleotide reductase holoenzyme which accumulates in the outer nuclear membrane from which they supply deoxyribonucleotide precursors to intranuclear replication enzymes. At the end of the S phase, the cell reduces M1 gene expression and resumes degrading 88 to 90 kDa M1 subunits. At least some of the 40 kDa M1 fragments are still active and can form partially active "holoenzymes" when mixed with a standard preparation of functional M2 subunits. The M1 control mechanism appears not to operate in hepatoma cells and Ehrlich ascites tumor cells, both of which maintain a pool of undegraded 88 to 90 kDa M1 components.
 ...
PMID:Ribonucleotide reductase--new twists in an old tale. 269 42

Minimal deviation hepatoma (Hepa) cells, from the mouse hepatoma B7756, synthesize and secrete haemopexin and express both the haemopexin receptor and the membrane haem-binding protein (MHBP) associated with the receptor, making this cell line the first available for detailed study of both haemopexin metabolism and hepatic transport. The 17.5 kDa MHBP was detected in Triton X-100 extracts of Hepa cells by immunoblotting with goat anti-rabbit MHBP. Scatchard-type analysis of haem-125I-haemopexin binding at 4 degrees C revealed 35,000 receptors per cell of high affinity (Kd 17 nM). Haemopexin-mediated haem transport at 37 degrees C is saturable, having an apparent Km of 160 nM and a Vmax. of 7.5 pmol of haem/10(6) cells per h during exponential growth. Haem-transport capacity is highest in the period just before the cells enter their exponential phase of growth and slowest in stationary phase. Interestingly, haem-haemopexin serves as effectively as iron-transferrin as the sole source of iron for cell growth by Hepa cells. Furthermore, depriving Hepa cells of iron by treatment with desferrioxamine (DF) increases the number of cell-surface haemopexin receptors to 65,000 per cell and consequently increases haemopexin-mediated haem transport. The effects of DF do not appear to require protein synthesis since they are not prevented by cycloheximide. Treatment of Hepa cells with hydroxyurea, an inhibitor of the iron-requiring enzyme ribonucleotide reductase that is obligatory for DNA synthesis, enhanced haemopexin-mediated haem transport. Thus, these studies provide the first evidence for regulation of haem transport by the iron status of cells and suggest a linkage between haemopexin, iron homeostasis and cell growth.
 ...
PMID:Expression of the haemopexin-transport system in cultured mouse hepatoma cells. Links between haemopexin and iron metabolism. 285 10

We measured both pyridine nucleotide levels and ribonucleotide reductase-specific activity in Yoshida ascites hepatoma cells as a function of growth in vivo and during recruitment from non-cycling to cycling state in vitro. Oxidized nicotinamide adenine dinucleotide (NAD+) and reduced nicotinamide adenine dinucleotide (NADP) levels remained unchanged during tumour growth, while NADP+ and reduced nicotinamide adenine dinucleotide phosphate (NADPH) levels were very high in exponentially growing cells and markedly decreased in the resting phase. Ribonucleotide reductase activity paralleled NADP(H) (NADP+ plus NADPH) intracellular content. The concomitant increase in both NADP(H) levels and ribonucleotide reductase activity was also observed during G1-S transition in vitro. Cells treated with hydroxyurea showed a comparable correlation between the pool size of NADP(H) and ribonucleotide reductase activity. On the basis of these findings, we suggest that fluctuations in NADP(H) levels and ribonucleotide reductase activity might play a critical role in cell cycle regulation.
 ...
PMID:Relationship between pyridine nucleotide levels and ribonucleotide reductase activity in Yoshida ascites hepatoma AH130. 353 72

3, 4, 5-Trihydroxybenzohydroxamic acid (VF 122), an inhibitor of ribonucleotide reductase, killed rat hepatoma 3924A cells in tissue cultured after 7 days of incubation. A concentration of 15 microM caused 50% inhibition of colony-forming ability (IC50). Under the same conditions, hydroxyurea, also an inhibitor of ribonucleotide reductase, had an IC50 of 52 microM. Treatment for 1 hr with VF 122 of exponentially growing culture resulted in a biphasic exponential dose-response curve (Do = 0.5 mM, IC50 = 0.75 mM, and Do = 1.8 mM, IP = 0.8 mM). In plateau-phase cells, a threshold exponential curve was obtained (Do = 2.2 mM, Dq = 1.7 mM, and IC50 = 2.7 mM). Exponentially growing hepatoma 3924A cells were more sensitive to VF 122 than were plateau-phase cultures. In contrast, hydroxyurea killed only exponentially growing 3924A hepatoma cells, exhibiting an exponential plateau dose-response curve without achieving achieving an IC50 value at concentrations from 1 to 200 mM. In synchronized cultures, VF 122 (1 MM for 1 hr) was toxic for cells in mid and late G1 phase, in early and mid S phase, and, to a lesser degree, in G2 phase, Hydroxyurea (10 mM for 1 hr) killed cells only in S phase. Proliferating and resting hepatoma 3924A cells recovered from sublethal and potentially lethal damage induced by VF 122.
 ...
PMID:Cytotoxic and cell kinetic effects of 3,4,5-trihydroxybenzohydroxamic acid (VF 122) in hepatoma 3924A cells. 713 48

Iron is essential for the growth of all living cells. One of the most important intracellular roles of iron is the activation of ribonucleotide reductase, which is indispensible to the production of deoxyribonucleotide necessary for DNA synthesis. Deferoxamine (DFO) is an iron chelating agent and has been known to have an antiproliferative effect in various malignant cells including hepatocellular carcinoma and the effect seems to be related to depletion of iron. This study was undertaken to investigate the effect of DFO on preneoplastic lesions in chemically induced hepatocarcinogenesis. The resistant hepatocyte model was used and Sprague Dawley rats were divided into the following groups; I: normal control, II: carcinogen administered group, III: carcinogen and DFO administered group. Rats were sacrificed at 3 days, 1 week, 2 weeks, 3 weeks, 4 weeks and 8 weeks after partial hepatectomy (PH). DFO (50 mg/kg/day, I.P.) was daily injected from 3 weeks before administration of carcinogen to the time when rats were sacrificed. Hepatic iron content was higher in group II than in group III, especially at 3 days and 1 week after PH. Hyperplastic lesions of resistant hepatocytes were less well developed in group III than in group II. Bromodeoxyuridine labelling indices of oval cells and hyperplastic lesions of resistant hepatocytes were higher in group II than in group III except for rats examined at 3 days after PH. The results suggest that DFO has an antiproliferative effect on preneoplastic lesions in hepatocarcinogenesis and it might be related to reduction of the hepatic iron.
 ...
PMID:The effect of deferoxamine on the preneoplastic lesions in the chemically induced hepatocarcinogenesis. 787 42

The ribonucleotide reductase inhibitor, hydroxyurea (HU), augments the cytotoxic effects of 5-fluorouracil (5FU) in vitro; both drugs are synergistic with interferon-alpha (IFN) in vitro. The aim of this phase I study was to determine the maximal duration of HU, 4.3 g/m2, administered as a parenteral infusion in combination with 5FU, 2.6 g/m2 administered over 24 hrs each week, + IFN, 9 MU, subcutaneously three times per week. There were 26 patients enrolled and evaluable. This included 14 patients with colorectal cancer of whom 13 had been previously treated, and 12 patients with other refractory malignancies (pancreas, cholangiocarcinoma, hepatocellular carcinoma, renal cell carcinoma, and others), of whom 10 were previously untreated. The dose-limiting toxicity of this regimen was myelosuppression. This prohibited dose escalation of HU above the starting dose (24 hrs) on a 6-weeks-on, 2-weeks-off therapy schedule. When filgrastim, 480 microg, was administered subcutaneously on days 3-6, the duration of HU could be extended to 48 hrs on a 2-weeks-on, 1-week-off therapy schedule. There were two instances of fatal infection, one in a patient with a rectovaginal fistula with neutropenic sepsis and the second in a patient with non-neutropenic Clostridium septicum sepsis. All therapy was administered in the ambulatory setting. There were three responders, all among previously untreated patients. High-dose parenteral hydroxyurea, 4.3 g/m2 administered over 24 hrs, can be safely combined with high-dose weekly 5FU, 2.6 g/m2 over 24 hrs + IFN, 9 MU subcutaneously three times per week, without filgrastim in the ambulatory setting. Parenteral hydroxyurea, 4.3 g/m2 over 24 hrs daily x 2 can also be combined with high-dose 5FU + IFN, but requires the addition of filgrastim to avoid severe myelosuppression.
 ...
PMID:Phase I trial of high-dose infusional hydroxyurea, high-dose infusional 5-fluorouracil and recombinant interferon-alpha-2a in patients with advanced malignancies. 882 49


1 2 Next >>