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)

A comparison of the cytidine 5'-diphosphate (CDP) and adenosine 5'-diphosphate (ADP) reductase activities from Ehrlich tumor cells was made to determine if the properties of the enzyme for these substrates were the same, except for the allosteric effector. It was observed that various purification steps did not result in an enzyme fraction that had a constant ratio of CDP:ADP reductase activities. The optimal Mg2+ ion concentration for CDP reduction was 3 to 4 mM, while the optimal Mg2+ ion concentration for ADP reduction was 0.1 mM inhibited ADP reduction. CDP reduction was relatively insensitive to the presence of dimethylformamide or dimethyl sulfoxide in the reaction mixture, but ADP reduction was decreased in the presence of these two compounds. Periodate-oxidized adenosine 5'-monophosphate, on incubation with the enzyme, had a greater effect on CDP reduction but little or no effect on ADP reduction. The response of the CDP and ADP reductase activities to the same negative effector was essentially the same. Both CDP and ADP reductions showed similar decreases in the presence of various concentrations of deoxyadenosine 5'-triphosphate. These data suggest that the Ehrlich tumor cell reductase enzyme system could consist of at least two different enzymes that may be regulated by the same allosteric protein.
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PMID:Comparison of the cytidine 5'-diphosphate and adenosine 5'-diphosphate reductase activities of mammalian ribonucleotide reductase. 16 52

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.
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PMID:Mechanism of action of inosine dialdehyde (NSC 118994) in the inhibition of proliferation of tumor cells in culture. 19 37

It had been shown previously that the ribonucleotide reductase from mouse tumor consisted of two nonidentical components (Tris and dye fractions, each prepared from the 20 to 40% (NH/)2SO4 protein fraction containing the ribonucleotide reductase activity by blue dextran-Sepharose chromatography). The individual components either separated or present in the intact enzyme can be specifically and independently inhibited by different compounds. The Tris fraction component was inhibited by 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone while the dye fraction component was inactivated by pyridoxal phosphate:BH4- and the dialdehyde derivative of inosine (Inox) and 5'-deoxyinosine prepared by the periodate oxidation of inosine and 5'-deoxyinosine. The intact enzyme could be completely inhibited by any of these compounds. Reductase activity was restored by reconstitution with the exogenous components. The individual components of the reductase in the intact Ehrlich tumor cell could also be specifically inhibited. Activity in the crude cell-free extracts prepared from 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone- or Inox-treated cells was restored by the addition of the appropriate exogenous component. These data suggest that combinations of inhibitors of ribonucleotide reductase which specifically inhibit the components may be useful in the treatment of cancer.
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PMID:Specific inhibitors directed at the individual components of ribonucleotide reductase as an approach to combination chemotherapy. 49 90

Ribonucleotide reductase from Ehrlich tumor cells was separated by chromatography on blue dextran/Sepharose into two protein fractions (Tris and Dye fractions). Neither fraction alone had reductase activity, but when combined, constituted an active enzyme system. Heat treatment of either fraction resulted in an inactive combination. The approximate molecular size of the active component of the Tris and Dye fractions was determined to be 5.7 S and 6.5 S, respectively, compared to 9 S for the intact enzyme. The Tris fraction was inactivated by hydroxylamine while the dye fraction was inactivated by pyridoxal phosphate/BH4-treatment. The inactivation of the Dye fraction was prevented by ATP. These data would indicate that the Tris and Dye fractions were comparable in function to the B2 and B1 proteins, respectively, of the Escherichia coli ribonucleotide reductase.
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PMID:Reconstitution of the ribonucleotide reductase enzyme from Ehrlich tumor cells. 56 57

The chemical class of drugs known as the nitrosoureas are a recently developed group of very active alkylating-agent anticancer drugs which are best represented by BCNU, CCNU, and methyl-CCNU (meCCNU). The nitrosoureas are among the most active, if not the most active, anticancer drugs both quantitatively (log kill of sensitive tumor cells in vivo) and qualitatively (spectrum of mouse, rat, and hamster tumors responding to treatment). Therapeutic anticancer activity of the nitrosoureas has been consistently observed with oral as well as parenteral administration. The nitrosoureas are clearly the most active group of anticancer drugs observed against experimental meningeal leukemias and intracerebrally implanted transplantable primary tumors of central nervous system origin (eg, gliomas, ependymoblastomas, and astrocytomas in mice and hamsters). The nitrosoureas have been observed to be less than additive in lethal toxicity for vital normal cells in the mouse in combination with representatives of the other major classes of anticancer agents, eg, purine antagonists, pyrimidine antagonists, inhibitors of DNA polymerase(s) or ribonucleotide reductase(s), mitotic inhibitors, drugs that bind to or intercalate with DNA, and other alkylating agents. Therapeutic synergism against one or more transplantable or spontaneous tumors of mice, rats, or hamsters with one of several nitrosoureas in two-drug combinations with representatives of most of the major classes of anticancer agents listed above has been reported. With a number of advanced-stages mouse tumors, generally considered to be refractory to treatment with most anticancer agents, long-term cures have been obtained with combination-drug or combined-modality (surgery plus chemotherapy) treatment. The demonstrated lack of cross-resistance of several leukemias and solid tumors of mice selected for resistance to BCNU, meCCNU, or other alkylating agents suggests that the widely held opinion that all alkylating agents are very similar in biologic mechanism of action, and therefore resistance to one alkylating agent probably predicts cross-resistance to all alkylating agents, may no longer be tenable. If not, then alkylating-agent drug combinations, either used alone or combined with other treatment modalities (eg, surgery) which have been reported to result in therapeutic improvement in a number of experimental murine tumor systems, may be indicated for serious consideration as surgical adjuvant chemotherapy by surgeons or as primary therapy by medical oncologists.
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PMID:Nitrosoureas: a review of experimental antitumor activity. 78 94

Periodate-oxidized inosine (Inox; NSC 118994) and periodate-oxidized 5'-inosinic acid (PI-IMP) were prepared and studied for their effects on ribonucleotide reductase activity in partially purified extracts from Ehrlich tumor cells and on nucleic acid synthesis in intact tumor cells in culture. Ribonucleotide reductase activity in cell-free extracts from Ehrlich tumor cells was inhibited by Inox and PI-IMP. PI-IMP was more inhibitory to the reductase activity than was Inox. Furthermore, the inhibition of ribonucleotide reductase activity by Inox and PI-IMP was greater for cytidine-5'-diphosphate reductase activity than for adenosine-5'-diphosphate reductase activity. The ribonucleotide reductase activity in cell-free extracts prepared from Ehrlich tumor cells treated with Inox or PI-IMP in culture was decreased compared with the activity in the extracts from untreated cells. Incorporation of labeled cytidine into the RNA and DNA of Ehrlich tumor cells in culture was inhibited by both Inox and PI-IMP. The conversion of cytidine to deoxycytidine nucleotides in the acid-soluble pool was likewise inhibited. These data indicate that Inox and PI-IMP inhibit the ribonucleotide reductase step as one of the sites of action of these compounds. However, the inhibition of RNA synthesis indicates that there must be additional sites of action of these nucleoside analogs.
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PMID:Inhibition of ribonucleotide reductase activity and nucleic acid synthesis in tumor cells by the dialdehyde derivatives of inosine (NSC 118994) and inosinic acid. 98 50

Ribonucleotide reductase activity in a partially purified enzyme preparation from Ehrilich tumor cells was inhibited by the dialdehyde derivatives of adenosine, 5-adenylic acid, and adenosine 5-triphosphate (prepared by the periodate oxidation of adenosine 5-adenylic acid, and adenosine 5-triphosphate). The borohydride-reduced derivative of periodate-oxidized adenosine was not inhibitory to the ribonucleotide reductase activity, showing that the aldehyde moiety was important in the inhibitory interactions of these compounds. This suggested the formation of a Schiff base between the dialdehyde derivative and an amino group (presumably, the epsilon-amino group of lysine). Pyridoxal phosphate, which is known to inhibit enzymes that have lysyl residues in the catalytic or allosteric sites, was an inhibitor of ribonucleotide reductase. Pyridoxal, pyridoxamine phosphate, pyridoxamine, and pyridoxine were not inhibitors. Borohydride reduction of the enzyme in the presence of pyridoxal phosphate produced a protein fraction that had little reductase activity remaining. The inhibition by pyridoxal phosphate was not influenced by increasing the substrate concentration (cytidine 5-diphosphate or adenosine 5-diphosphate), but was diminished by increasing the ratio of allosteric effector to pyridoxal phosphate concentrations, suggesting an interaction of pyridoxal phosphate at the regulatory site of ribonucleotide reductase. The addition of adenosine 5-triphosphate to the pyridoxal phosphate-enzyme mixture, which was subsequently treated with borohydride, partially prevented the inhibition by pyridoxal phosphate. Heat treatment of the ribonucleotide reductase enzyme preparation in the presence of pyridoxal phosphate protected the enzyme against loss of cytidine 5-diphosphate and adenosine 5-diphosphate reductase activities.
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PMID:Studies on mammalian ribonucleotide reductase inhibition by pyridoxal phosphate and the dialdehyde derivatives of adenosine, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. 110 3

Gemcitabine (dFdC) and DMDC are new antimetabolites with good antitumor activities against various tumors which include human leukemic cell lines and a number of rodent and human solid tumors and human tumor. They are structurally related to cytarabine (Ara-C) which is known as one of the most effective drugs against adult acute leukemia, but many solid tumors are insensitive not been found to the drug. Gemcitabine acts as an inhibitor of ribonucleoside diphosphate reductase and inhibits DNA synthesis. Biochemically Gemcitabine is rapidly phosphorylated to dFdCTP which has a comparatively longer half-life than that of Ara-C, showing a therapeutic activity against tumors. In the phase I trials, the reported maximum-tolerated doses were 790 mg/m2 to 1370 mg/m2 at the schedule of 30 minutes i.v. infusion once a week for three weeks but higher dose levels (2,500 mg/m2 to 4,800 mg/m2) were reported in the schedule of prolongation of the infusion time. Reported toxicities were myelosuppression, fatigability, fever, appetite loss and skin rash. Toxicities were seemed to be mild. In USA, Europe and South Africa, phase II trials of Gemcitabine at the schedule of 30 minutes infusion once a week for three weeks followed by one week rest were performed against solid tumors (breast cancer, ovarian cancer, renal cancer, colorectal cancer, pancreas cancer, head and neck cancer, and lung cancer) and showed good responses to those tumors. DMDC was developed in Japan, and a phase I trial is currently on-going.
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PMID:[New antitumor antimetabolites--gemcitabine and DMDC]. 133 22

A rapid elevation of ribonucleotide reductase activity was observed with BALB c/3T3 fibroblasts treated with 10 nM okadaic acid, a nonphorbol ester tumor promoter and protein phosphatase inhibitor. Northern blot analysis of the two components of ribonucleotide reductase (R1 and R2) showed a marked elevation of R1 and R2 mRNA expression. Western blot analysis with R1 and R2 specific monoclonal antibodies indicated that the increase in ribonucleotide reductase activity was primarily due to the elevation of the R2 rather than the R1 protein during treatment with okadaic acid. The okadaic acid induced elevations in R1 and R2 message levels occurred without a detectable change in the proportion of cells in S phase and were blocked by treatment of cells with actinomycin D, indicating the importance of the reductase transcriptional process in responding to the action of okadaic acid. Furthermore, down-regulation of protein kinase C with 12-O-tetradecanoylphorbol-13-acetate pretreatment abrogated the okadaic acid mediated elevation of ribonucleotide reductase mRNAs, consistent with the involvement of this signal pathway in the regulation of ribonucleotide reductase and the effects of okadaic acid. Treatment of cells with 2.5 nM calyculin A, another non-phorbol ester tumor promoter and protein phosphatase inhibitor, resulted in a rapid elevation of both R1 and R2 mRNA levels within 10 min of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of mammalian ribonucleotide reductase by the tumor promoters and protein phosphatase inhibitors okadaic acid and calyculin A. 133 11

Carcinoma of the cervix is most commonly treated with radiotherapy when the disease is locally advanced. Tumor bulk often limits the efficacy of this therapy, as does the tolerance of adjacent healthy tissue. Cytotoxic chemotherapeutic agents have been used with concomitant radiotherapy. Extensive data are available on dose and schedule tolerance for cisplatin, 5-fluorouracil, and a number of combination regimens. Phase III data that confirm any advantage in terms of local control, disease-free survival, or overall survival have been published only for hydroxyurea. Hydroxyurea, an S-phase-specific inhibitor of ribonucleotide reductase, lacks single-agent activity against metastatic, squamous cell cervical cancer. Further studies are required before agents other than hydroxyurea can be considered standard therapy with concomitant radiotherapy for locally advanced carcinoma of the cervix.
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PMID:Concurrent chemoradiation in carcinoma of the uterine cervix. 150 85


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