Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibition by different p-alkoxyphenol derivatives of the growth-regulating enzyme ribonucleotide reductase (RR) in purified Escherichia coli and mouse R2 protein preparations was studied by EPR spectroscopy. The inhibitor-induced inactivation of the catalytic subunit protein R2 was measured at 77 degrees K by observing the decrease of the typical EPR signal from the functionally essential protein-linked tyrosyl free radical. p-Methoxy-, p-ethoxy-, p-propoxy-, and p-allyloxyphenol were about 2 orders of magnitude more effective in inhibiting mouse R2, compared with E. coli R2. Among the p-alkoxyphenols studied, p-propoxyphenol was the most effective inhibitor of mouse R2 (IC50, 0.7 microM) and p-methoxyphenol was the least effective (IC50, 11 microM); p-ethoxy- and p-allyloxyphenol were intermediate. The observed half-maximal inhibition values characterized p-alkoxyphenols as a new class of strong inhibitors of the R2 protein of mammalian RR. p-Propoxy-, p-ethoxy-, and p-allyloxyphenol could be considered as new candidates for anticancer drugs. A special cellular inhibition assay of RR in proliferating tumor cells, in which the tyrosyl radical of R2 at natural concentration was monitored by EPR, showed that the four para-substituted alkoxyphenols also inhibited the enzyme with high efficiency in tumor cells (IC50, between 0.5 microM and 5 microM). Our results with inactivation of protein R2 of RR imply that the cytostatic effect of p-alkoxyphenols on melanoma cells, which has been hitherto explained by inhibition of tyrosinase [Melanoma Res. 2:295-304 (1992)], may be caused at least partly by inhibition of RR. Protein R2 of RR may be considered as an additional target that could be used for future cancer chemotherapy.
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PMID:p-Alkoxyphenols, a new class of inhibitors of mammalian R2 ribonucleotide reductase: possible candidates for antimelanotic drugs. 818 56

The present study was designed to determine the mechanism by which orotic acid, a rat liver tumor promoter, inhibits DNA synthesis in normal hepatocytes in primary culture. Our results indicate that orotic acid inhibited the epidermal growth factor induced expression (mRNA) of both M1 and M2 subunits of ribonucleotide reductase while the expression of c-fos, c-myc, c-Ha-ras and beta-actin was not inhibited to any significant extent. These studies suggest that ribonucleotide reductase may be one target for orotic acid-induced mitoinhibition.
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PMID:Ribonucleotide reductase: a possible target for orotic acid induced mitoinhibition in normal hepatocytes in primary culture. 822 27

Polypeptide growth factors are a diverse group of biological regulators. Because they are fundamentally involved in the cellular processes that are important for transformation and progression to malignancy, alterations in growth factor control and in their signal pathways are often observed in tumor cells. In this review, we consider the participation of growth factors and the mechanisms by which they effect tumor progression, using as examples members of the transforming growth factor beta (TGF-beta) and fibroblast growth factor (FGF) families. We explore the hypothesis that although abrogation of TGF-beta negative growth regulation is necessary for transformation, in the later stages of tumor progression, TGF-beta plays a direct role in the enhancement of invasion and metastasis as an autocrine stimulator of these processes. In addition, we present evidence that demonstrates both the potential and the importance of members of the FGF family in transformation and induction of metastasis. Several models of growth factor regulation of malignancy are presented in which we demonstrate (1) a link between TGF-beta 1 mitogenic stimulation of malignant cells and alterations in the expression of ribonucleotide reductase, a key rate-limiting step in the synthesis of DNA and in cell proliferation; (2) autocrine and/or intracrine FGF mitogenic stimulation of malignant cell proliferation and metastasis; and (3) autocrine TGF-beta regulation of malignant cell locomotion and invasion through elevated proteolytic activity and increased synthesis of hyaluronan and RHAMM, a novel hyaluronan cell surface receptor.
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PMID:Transforming growth factor beta and fibroblast growth factor as promoters of tumor progression to malignancy. 824 21

2',2'-Difluorodeoxycytidine (Gemcitabine, dFdCyd) is a cytotoxic agent which is active toward a variety of tumor cells. It has been shown that there are multiple intracellular sites of action which include ribonucleotide reductase and DNA polymerase. In these studies, the effects of dFdCyd on wild-type mouse leukemia L1210 cells and variant L1210 cell lines which had alterations at the ribonucleotide reductase site or at the deoxyribonucleoside kinase site were studied. For cell growth, the IC50 value for dFdCyd in wild-type L1210 cells was 3.1 nM. In the variant cell lines, the IC50 values were: hydroxyurea-resistant (HU), 3.3 nM; deoxyadenosine-resistant (Y8), 1.8 nM; pyrazoloimidazole/deoxyadenosine-resistant (ED2), 1.9 nM; and deoxyguanosine-resistant (dGuo-R), 44.7 nM. The dGuo-R cell line had a relatively specific loss of the deoxyribonucleoside kinase responsible for phosphorylating deoxyguanosine and cytosine arabinoside with little loss of the deoxycytidine kinase activity. DFdCyd had no effect on the total uptake of [14C]cytidine into the cells or incorporation into RNA. DFdCyd inhibited the conversion of [14C]cytidine to deoxycytidine nucleotides and incorporation into DNA. However, the incorporation of cytidine into DNA was inhibited to a greater extent than was the inhibition of in situ ribonucleotide reductase activity. Ribonucleotide reductase activity in cell-free extracts prepared from L1210 cells treated with dFdCyd (20 nM) overnight was reduced by 50%. These results show that cell lines which have increased levels of ribonucleotide reductase activity (HU and ED2) or loss of feedback inhibition by dATP (ED2 and Y8) are still sensitive to dFdCyd. The findings indicate that ribonucleotide reductase is not the primary site of inhibition by dFdCyd.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of 2',2'-difluorodeoxycytidine (Gemcitabine) on wild type and variant mouse leukemia L1210 cells. 836 54

Using ESR spectroscopy, the ability of enzyme inhibitors to quench protein-derived tyrosyl radicals was studied in two different enzymes, prostaglandin H synthase and ribonucleotide reductase. The prostaglandin H synthase inhibitors indomethacin, eugenol, and MK-410 effectively prevent the formation of tyrosyl radicals during the oxidation of arachidonic acid by prostaglandin H synthase from ram seminal vesicles. A direct reaction with preformed tyrosyl radicals was observed only with eugenol. The other prostaglandin H synthase inhibitors were ineffective. The ribonucleotide reductase inhibitors hydroxyurea and 4-hydroxyanisole, which effectively inactivate the tyrosyl radical in the active site of ribonucleotide reductase present in tumor cells, exhibit a different reactivity with tyrosyl radicals formed by prostaglandin H synthase. Hydroxyurea quenches preformed tyrosyl radicals in prostaglandin H synthase weakly, whereas 4-hydroxyanisole does not quench tyrosyl radicals in prostaglandin H synthase at all. Eugenol, which quenches preformed prostaglandin H synthase-derived tyrosyl radicals, also quenches the tyrosyl radical in ribonucleotide reductase. The results suggest that the reactivity of protein-linked tyrosyl radicals in ribonucleotide reductase and those formed during prostaglandin H synthase catalysis are very different and have unrelated roles in enzyme catalysis.
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PMID:ESR studies on reactivity of protein-derived tyrosyl radicals formed by prostaglandin H synthase and ribonucleotide reductase. 838 Sep 61

Time-related changes have been studied in the content of extracellular DNA, Fe(3+)-transferrin (TF), and Cu(2+)-ceruloplasmin (CP) in the blood plasma and the activity of ribonucleotide reductase (RR) in the tumor cells and spleen of mice during the development of acute lympholeukosis P-388 and after ionizing irradiation. At the initial stages of leucosis P-388, the content of extracellular DNA increases, the TF and CP pools in the blood plasma enlarge, and the RR activity in the tumor cells and spleen of tumoral mice markedly increases. A dose-dependent increase in RR activity was also recorded in the spleen of 5-day-old rats within 15-30 min after irradiation. The causes of these changes and the possibility for these indices to be used in estimating leucosis risk are discussed. Radiation-induced increases in RR activity are discussed in relation to the SOS-response to DNA damage; an increased pool of deoxyribonucleotides is necessary for repair of DNA. The mean contents of extracellular DNA, TF and CP in the blood plasma were obtained from children of different ages degrees of radioactive contamination suffering the consequences of the accident at the Chernobyl' Nuclear Power Station (n = 155). Groups of children have been isolated with increased, sharply decreased, and close to normal levels of extracellular DNA, TF, and CP. The lowered TF pool was observed in children with thyroid glands damaged by incorporated radioactive iodine with the degree of suppression determined by the dose. For most children subject to general irradiation, the TF and CP pools in the blood were higher than in the control, suggesting an adaptive response to irradiation.
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PMID:[Markers of the metabolic changes arising as a result of ionizing radiation exposure]. 854 87

MDL 101,731, (E)2'-fluoromethylene-2'-deoxycytidine, is an irreversible inhibitor of ribonucleotide diphosphate reductase and causes regression of human tumors in nude mouse models. Messenger RNA levels for testosterone-repressed prostatic message-2 (TRPM-2), a transcript that increases in human tumor xenografts undergoing programmed cell death, were analyzed by in situ hybridization. Xenografts derived from a human prostate tumor cell line (PC-3) regressed following treatment with MDL 101,731 and the relative levels of TRPM-2 mRNA increased up to threefold in drug-treated animals. Apoptosis in the tumor xenografts was further indicated by in situ labeling of DNA strand breaks by incorporation of biotinylated-dUTP with terminal deoxynucleotidyl transferase. In vitro, PC-3 cells incubated with MDL 101,731 showed evidence of apoptosis based on flow cytometry and DNA laddering. These data support the hypothesis that MDL 101,731 stimulates programmed cell death in regressing PC-3 xenografts.
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PMID:A ribonucleotide reductase inhibitor, MDL 101,731, induces apoptosis and elevates TRPM-2 mRNA levels in human prostate tumor xenografts. 854 73

Mammalian ribonucleotide reductase is a highly regulated activity essential for DNA synthesis and repair. The 3'-untranslated region (3'-UTR) of mammalian ribonucleotide reductase R2 mRNA has been implicated in the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate-mediated stabilization of mouse BALB/c 3T3 R2 message. We investigated the possibility that the 3'-UTR contains regulatory information for R2 mRNA turnover. Using 3'-end-labeled RNA in gel shift and UV cross-linking analyses, we detected in the 3'-UTR a novel 9-nucleotide cis-element, 5'-UCGUGUGCU-3', which interacted with a widely distributed cellular cytosolic protease-sensitive factor(s) in a sequence-specific manner to form a 45-kDa R2 binding protein complex. The binding activity was redox-sensitive and down-regulated by 12-O-tetradecanoylphorbol-13-acetate and okadaic acid in a dose-dependent manner. Insertion of a 154-base pair fragment containing the cis-element led to markedly reduced accumulation of chloramphenicol acetyltransferase hybrid mRNA relative to the same insert carrying a series of G --> A mutations within this element that eliminated binding. We suggest that the 9-nucleotide region functions as a destabilizing element. These results provide a model for ribonucleotide reductase gene expression through a novel and specific mRNA cis-trans-interaction involving a phosphorylation signal pathway that leads to changes in the stability of R2 message.
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PMID:Defining a novel cis-element in the 3'-untranslated region of mammalian ribonucleotide reductase component R2 mRNA. cis-trans-interactions and message stability. 870 35

Mammalian ribonucleotide reductase is rate limiting for the synthesis of DNA. The active enzyme is composed of two dissimilar components called R1 and R2, encoded by different genes. The 3' untranslated regions (3' UTRs) of R1 and R2 messages contain sequences that are important in regulating gene expression through changes in message stability. We have constructed expression plasmids containing the R1 or R2 mRNA 3' UTRs, and we show that transfection of these plasmids into highly malignant mouse 10 T1/2 cells significantly suppresses the tumorigenic properties of these cells in syngeneic mice when compared with cells transfected with the same plasmid lacking R1 or R2 3' UTR sequences or when compared with cells transfected with the same plasmid expressing a heterologous sequence as a control. Furthermore, cells expressing the R2 3' UTR exhibit significantly reduced potential to disseminate to the lungs of syngeneic animals in experimental metastasis assays. The tumor-suppressive effects of the mouse R1 and R2 3' UTRs were not confined to mouse cells, because human HeLa cells transfected with expression plasmids containing either RI or R2 3' UTRs were also significantly less tumorigenic in assays using BALB/c nu/nu mice. These studies demonstrate that the untranslated regions of ribonucleotide reductase mRNAs can function as modifiers of tumor cell development and for the more complex process of tumor dissemination. We propose that these malignancy-suppressive effects are mediated through RNA interactions with cellular components involved in growth regulation through mechanisms of posttranscriptional control of gene expression. In addition, these observations emphasize the enormous potential of untranslated RNA to act directly as modifiers of biological characteristics relevant to mechanisms of malignancy.
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PMID:Suppression of malignancy by the 3' untranslated regions of ribonucleotide reductase R1 and R2 messenger RNAs. 881 26

The present study investigated the ability of a recombinant herpes simplex virus type 1 (HSV) vector to deliver genes into disseminated brain tumor foci through intrathecal injection of the vector. The animal model was designed to simulate brain tumors with cerebrospinal fluid (CSF) metastases, which are found especially in the pediatric population. 9L gliosarcoma cells were injected both into the right frontal lobe and in through the cisterna magna of adult rats. The HSV vector, hrR3, was inoculated intrathecally 5 days later. This vector is defective in the gene for ribonucleotide reductase, and, therefore, replicates preferentially in dividing cells; it retains an intact HSV-thymidine kinase gene (HSV-tk). Two days after injection of the vector, immunohistochemical staining for HSV thymidine kinase (HSV-TK) revealed expression in frontal tumors, as well as in leptomeningeal tumor foci along the entire neuroaxis. HSV-TK-immunopositive cells were most frequent in small tumors contacting the CSF pathways. Frontal lobe tumors showed the highest density of HSV-TK-immunopositive cells around their periphery with little expression in central parts. Some paraventricular neurons temporarily showed HSV-TK-immunolabeling at this early time point. The number of HSV-TK-immunopositive tumor cells markedly decreased 5 days after injection of the HSV vector. In all animals, some toxicity was observed in the first 2-4 days after virus injection with extensive leptomeningeal inflammation. In conclusion, intrathecal application of HSV vectors can mediate widespread transfer of the therapeutic HSV-tk gene into disseminated tumors throughout the brain and CSF pathways. Although there was marked toxicity associated with intrathecal injection of this vector, this mode of gene delivery offers a promising approach for treatment of CSF-metastases in conjunction with development of less toxic vectors.
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PMID:Herpes vector-mediated delivery of marker genes to disseminated central nervous system tumors. 883 17


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