Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies have suggested that the alpha class glutathione S-transferase (GST) may protect cells from the chemotherapeutic drugs chlorambucil and melphalan. In order to further define the function of human alpha class GST, a complementary DNA which encodes it was ligated into an expression vector under the direction of the human metallothionein-IIA promoter and stably transfected into human MCF-7 breast cancer cells in conjunction with the G418-selectable plasmid pSV2neo. Clonal cell lines were identified which expressed increased levels of GST enzyme activity (2.2- to 5.6-fold). The transfected cell lines also had increased peroxidase activity using cumene hydroperoxide as the substrate (1.9- to 3.8-fold) which is consistent with the intrinsic peroxidase activity of alpha class GSTs. Southern blot analysis indicated that genomic DNA from these cells contained a fragment indistinguishable from the transfected alpha class GST complementary DNA (850 base pairs); Northern blot analysis of total cellular RNA indicated that these cells contained appropriately sized alpha class GST RNA (980 nucleotides); and Western blot analysis indicated that, while MCF-7 cells contained no detectable alpha class GST protein, the transfected cells contained markedly elevated levels of alpha class GST but no detectable mu or pi class GST. These alpha class GST transfected cells had increased resistance to ethacrynic acid (2.1- to 3.0-fold). However, the transfected cells failed to show any increased resistance measured at the drug dosage which inhibited 50% of the colony formation to the chemotherapeutic drugs chlorambucil, melphalan, Adriamycin, or cisplatin under conditions of either continuous or 1-h drug exposure. Neither was there any change in sensitivity to the cytotoxins benzo(a)pyrene, benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (anti), or 1-chloro-2,4-dinitrobenzene. These studies indicate that expression of this human alpha class GST by itself in MCF-7 human breast cancer cells does not confer resistance to the chemotherapeutic drugs tested under the conditions used in these studies.
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PMID:Antineoplastic drug sensitivity of human MCF-7 breast cancer cells stably transfected with a human alpha class glutathione S-transferase gene. 198 77

We have characterized a new selenium-dependent glutathione peroxidase, GSHPx-GI, by expressing a GSHPx-GI cDNA isolated from human hepatoma HepG2 cells in human mammary carcinoma MCF-7 cells, which have virtually undetectable expression of either the classical cellular enzyme, GSHPx-1, or GSHPx-GI at the protein level. One of the G418-resistant clones, neo-D1, expresses the transfected GSHPx-GI cDNA. This is based on 1) the presence of an additional GSHPx-GI DNA restriction fragment detected by Southern analysis; 2) the presence of a 1.9-kilobase (kb) GSHPx-GI mRNA in addition to the 1.0-kb endogenous mRNA by Northern analysis; and 3) the appearance of a 22-kDa 75Se-labeled protein which is absent in parental MCF-7 cells revealed by SDS-polyacrylamide gel electrophoresis. GSHPx-GI expressed in neo-D1 is a tetrameric protein localized in cytosol. GSHPx-GI does not cross-react with antisera against human GSHPx-1 or human plasma glutathione peroxidase (GSHPx-P). Similar substrate specificities are found for GSHPx-1 and GSHPx-GI; they both catalyze the reduction of H2O2, tert-butyl hydroperoxide, cumene hydroperoxide, and linoleic acid hydroperoxide with glutathione, but not of phosphatidylcholine hydroperoxide. GSHPx-GI mRNA was readily detected in human liver and colon, and occasionally in human breast samples, but not other human tissues including kidney, heart, lung, placenta, or uterus. In rodent tissues, GSHPx-GI mRNA is only detected in the gastrointestinal tract, and not in other tissues including liver. In fact, GSHPx-GI appears to be the major glutathione-dependent peroxidase activity in rodent GI tract. This finding suggests that GSHPx-GI could play a major role in protecting mammals from the toxicity of ingested lipid hydroperoxides. In conclusion, we have demonstrated that GSHPx-GI is the fourth member in the selenium-dependent glutathione peroxidase family, in addition to GSHPx-1, GSHPx-P, and phospholipid hydroperoxide glutathione peroxidase (PHGPX).
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PMID:Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI. 842 33

Interleukin-8 (IL-8) is a chemokine for neutrophils and an angiogenic factor. Human tumors that express IL-8 may exhibit intense neutrophil infiltration and increased vascularization. Mutatect cells are a murine fibrosarcoma that can be grown as subcutaneous tumors in syngeneic C57BL/6 mice. Since neutrophils are a source of cytotoxic and genotoxic species, we constructed Mutatect cell lines that constitutively express human IL-8 to explore the involvement of neutrophils in tumor biology and genetic instability. An IL-8/neo expression plasmid was stably transfected into Mutatect MC17-51 cells and clone MIL-4 was isolated. Tumors initiated with 5x10(5) MIL-4 cells grew very slowly compared with tumors from pure MC17-51 cells or from 0.5 to 4x10(5) MIL-4 cells mixed with 5x10(5) MC17-51 cells. Over 95% of cells recovered from slow-growing pure MIL-4 tumors lost the transgene as measured by loss of (i) resistance to G418, (ii) expression of IL-8 protein and (iii) IL-8-specific DNA sequences. When tumors from mixed cell types were examined, loss of the transgene did not occur; rather, IL-8 producing cells appeared to have some growth advantage. The neutrophil content of tumors (as measured by myeloperoxidase) was directly proportional to the level of IL-8 expressed at the time tumors were excised. As reported earlier, the frequency of mutations at the hypoxanthine phosphoribosyltransferase locus was also directly proportional to neutrophil content. To explain some of these biological findings, we postulate that early in development of pure MIL-4 tumors, genotoxic/cytotoxic neutrophils are attracted by IL-8, which in turn leads to loss of the transgene and to localized cytotoxicity of IL-8 producing cells. In mixed tumors, where the initial IL-8 concentration may be lower, tumors might become established more readily because fewer neutrophils may be attracted. This relatively simple experimental paradigm has revealed some of the complex biological changes that can occur as a result of IL-8 in tumors.
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PMID:Constitutive expression of interleukin-8 by Mutatect cells markedly affects their tumor biology. 1118 44