Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The use of Mabs for the detection and treatment of human carcinoma lesions can still be regarded in its infancy. As with other new approaches to cancer therapy, several conceptual as well as real problems exist when designing clinical protocols for Mab-directed immunotherapy. From the Mab standpoint, studies using the intact IgG have shown that, in a majority of patients injected with IgG, human anti-mouse IgG antibodies develop that hamper the effectiveness of subsequent antibody administration. It is believed that the human anti-mouse antibody response is directed against the Fc region of the IgG molecule. The elimination of this region through fractionation of the Mab to obtain the minimum binding site could result in a less immunogenic molecule. Another approach aimed at reducing the immunogenicity of the Mab would be to clone the genes encoding for individual Mabs, reduce them via restriction endonuclease techniques, and insert human immunoglobulin constant regions. The resulting chimeric antibodies are believed to reduce the development of human anti-mouse antibodies. Effective Mab therapy of human tumor lesions may also be achieved through the recruitment of a portion of the host's immunologic defense system. An example is the use of anti-idiotype Mabs that use as immunogen a Mab to a tumor antigen. The anti-idiotype antibodies are selected for binding to the antigen binding, or idiotype, region of the first Mab. The binding sites of the new anti-idiotype Mabs should reflect the 'internal image' of the original antigen. The anti-idiotype antibodies may be used to immunize patients (i.e., vaccines) in an attempt to mount an active immune response against the antigen-positive tumor cells. Recent studies have shown a synergism between interferon-alpha and an anti-idiotype Mab for the in-vivo antitumor activity in a murine B-cell lymphoma experimental model. Whether an interferon-mediated increase in the tumor antigen or the Fc receptor was part of the synergism was not investigated. Mabs alone have also been shown to elicit cytotoxic activity in vitro and tumoricidal activity in vivo. Antibodies of the IgG2a isotype can direct macrophage-mediated cytotoxicity. These studies revealed the importance of the number of antibody sites per cell as well as the number of cells that bind the IgG2a Mab, thus suggesting a 'threshold' requirement for the demonstration of effective tumor cell lysis in vitro and in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Augmentation of tumor antigen expression by recombinant human interferons: enhanced targeting of monoclonal antibodies to carcinomas. 197 58

RD-114 is a human sarcoma-derived cell line which is chronically infected with the RD-114 retrovirus. In a previous study, we found that treatment of these cells with human interferon-alpha or human interferon-gamma causes a marked inhibition of RD-114 virus production, but that the replication of exogenous vesicular stomatitis or encephalomyocarditis virus is not impaired. In the present study, we report that neither type of interferon has strong inhibitory effects on DNA synthesis or on multiplication of the cells. We also failed to detect a double-stranded RNA-dependent protein kinase activity in extracts of both interferon-treated and untreated cells. However, a low level of 2',5'-oligoadenylate [2,5(A)] synthetase activity was detectable in extracts of interferon-treated cells. 2,5(A)-dependent endonuclease L activity was detectable in extracts of both untreated and interferon-treated cells. This was probably responsible for the inhibition of protein synthesis observed upon introduction of 2,5(A) to RD-114 cells. In many cells, interferon has been found to induce synthesis of several proteins demonstrable by autoradiographic analysis of slab gels on which extracts of interferon-treated and radiolabelled cells are separated. Using a similar method, no such induced protein synthesis was detectable in interferon-treated RD-114 cells. Our results indicate that RD-114 cells are resistant to most known actions of interferons except for the antiretroviral action to which they are as sensitive as any other cell line.
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PMID:Antiviral, anticellular and enzyme-inducing activities of interferons in RD-114 cells. 619 49

Cloned human interferon complementary DNAs were used as hybridization probes to detect interferon alpha and beta gene families in restriction endonuclease digests of total genomic DNA isolated from a wide range of vertebrates and invertebrates. A complex interferon-alpha multigene family was detected in all mammals examined, whereas there was little or no cross-hybridization of human interferon-alpha complementary DNA to non-mammalian vertebrates or invertebrates. In contrast, human interferon-beta complementary DNA detected one or two interferon-beta genes in all mammals tested, with the exception of the cow and the blackbuck, both of which possessed a complex interferon-beta multigene family which has presumably arisen by a recent series of gene duplications. Interferon-beta sequences could also be detected in non-mammalian vertebrates ranging from birds to bony fish. Detailed restriction endonuclease mapping of DNA sequences neighbouring the interferon-beta gene in a variety of primates indicated a strong evolutionary conservation of flanking sequences, particularly on the 3' side of the gene.
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PMID:A comparison of vertebrate interferon gene families detected by hybridization with human interferon DNA. 630 47

The 2',5'-oligoadenylate (2-5A) synthetase pathway, induced by interferon-alpha (IFN-alpha), has been shown to be responsible for the antiviral action of IFN-alpha against some viruses. Studies were done to determine the role of this pathway in the anti-herpes simplex virus (HSV) action of IFN-alpha alone or in combination with acyclovir (ACV), a combination that leads to synergistic anti-HSV activity. Treatment of human corneal cells or Vero cells with 100 IU/ml of IFN-alpha induced expression of 2-5A synthetase mRNA and a 10-fold increase in 2-5A synthetase production compared with untreated cells. HSV infection alone did not induce 2-5A synthetase production, but when IFN-alpha-treated cells were infected with HSV, enzyme level was significantly increased (p < 0.05) compared with that in IFN-alpha-treated, uninfected cells. HSV infection actually decreased the level of 2-5A synthetase mRNA in IFN-alpha-treated cells. Although IFN-alpha treatment induced high levels of 2-5A synthetase with or without HSV infection, no activation of the latent endonuclease was detected by specific cleavage of ribosomal RNA. Treatment of infected cells with 5 microM ACV alone or combined with IFN-alpha did not increase 2-5A synthetase or endonuclease activities above those detected in cells not treated with ACV. The data indicate that the 2-5A synthetase pathway was inducible in corneal cells and Vero cells but did not appear to contribute to the anti-HSV activity of IFN-alpha alone or the synergistic activity of IFN-alpha combined with ACV.
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PMID:2',5'-oligoadenylate synthetase in interferon-alpha- and acyclovir-treated herpes simplex virus-infected cells. 764 30

In the 35 years since the discovery of interferon, significant biological activity has been described for interferon-alpha (IFN alpha) in various cancers, particularly haematological malignancies such as hairy cell leukaemia and chronic myelogenous leukaemia. Except for localised therapy in bladder and ovarian cancer, activity against most solid tumours has been disappointing. Other notable exceptions include Kaposi's sarcoma, renal cell carcinoma and malignant melanoma, tumours known to be susceptible to immunological attack. More recently, broad spectrum antiviral activity has been demonstrated for both recombinant and naturally occurring IFN alpha. Hepatitis C is responsive to IFN alpha in about 40% of patients, but long term remissions are rare. In contrast, long term suppression of hepatitis B is common following IFN alpha therapy. Both diseases respond in a dose proportional fashion, with daily doses of 5 million units (MU) significantly more effective than lower doses. The mechanism of action in viral diseases involves the expression of unique antiviral proteins such as endonuclease and 2'-5'-oligoadenylate synthetase which enhance the destruction of viral RNA. General cellular protein synthesis is also inhibited, including cytochrome P450 enzymes. This forms the basis for potential drug interactions, with IFN alpha slowing the clearance of highly metabolised drugs such as theophylline. As an antitumour agent, the mechanism of action of IFN alpha is unclear, particularly in haematological cancers. In melanoma and renal cell carcinoma, antitumour effects may be mediated by augmented immune responses including activation of natural killer lymphocytes and enhanced expression of cell surface antigens (e.g. MHC I and II). Conversely, antibody formation to recombinant IFN alpha may result in a loss of activity. This has been observed in both renal cell cancer and hepatitis B and C. The elimination half-life of IFN alpha is short, 4 to 5 hours, but biological activity extends for 2 to 3 days after administration, which facilitates daily or thrice weekly administration. Clearance of IFN alpha is mediated by catabolism in the renal tubules; no intact drug is excreted in the urine. It is probable that the antiviral indications of IFN alpha will expand as the agent is more clearly recognised as a primary endogenous defence against various viral conditions.
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PMID:Interferon-alpha in malignant and viral diseases. A review. 768 71

We describe the case of a 69-year-old man with systemic mastocytosis and severe osteopetrosis who carries a somatic activating mutation in the c-kit proto-oncogene. The patient initially presented with urticaria pigmentosa, progressing to systemic mast cell disease with severe anemia due to bone marrow involvement, chronic diarrhea, and hepatosplenomegaly. Direct sequencing using amplimers from reverse transcriptase-polymerase chain reactions (RT-PCR) from skin mast cell-derived RNA revealed a point mutation in the c-kit proto-oncogene at position 2468, introducing a new recognition site for the restriction endonuclease HinfI. Treatment with interferon-alpha 2a, prednisone, and erythropoietin was initiated. Subsequently, clinical symptoms improved significantly and hemoglobin levels are now stable at 13 g/dl.
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PMID:c-kit mutation and osteopetrosis-like osteopathy in a patient with systemic mast cell disease. 979 83

The 2'-5'-oligoadenylate (2-5A) synthetases are a family of interferon-alpha (IFN-alpha) inducible enzymes that block viral replication by activating a latent endonuclease during viral infections. In Ramos cells, induction of mRNAs for the intermediate isoform of 2-5A synthetase (p69) requires five-fold higher IFN-alpha than is required for induction of the small isoform (p40). The p40 and p69 isoforms are similarly induced between 1 and 24 h with maximal induction at 8 h. At 48 h, however, p69 is more strongly induced than p40. Induction of p69 and p40 between 1 and 24 h is protein synthesis independent whereas at 48 h, p69 induction becomes dependent on protein synthesis. Initial induction of both isoforms requires tyrosine kinase activation and is enhanced by activation of a separate signalling pathway by the tumour promoter, 12-0-tetradecanoyl phorbol-13-acetate (TPA). These data suggest that induction of the p40 is predominantly protein synthesis independent, whereas p69 induction occurs in two phases, an initial protein synthesis independent phase and a delayed protein synthesis dependent phase.
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PMID:Protein synthesis-dependent and -independent induction of p69 2'-5'-oligoadenylate synthetase by interferon-alpha. 1052 12