Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.1.17 (ornithine decarboxylase)
 6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dramatic changes in morphology induced by nanomolar doses of tumor-promoting agents, especially in epithelial cells, have been noted previously (Driedger and Blumberg, 1980; Rifkin et al., 1979; Croop et al., 1980; Phaire-Washington et al., 1980; Ohuchi and Levine, 1980; Ojakian, 1981; Fey and Penman, 1984). This chapter shows the effect of the tumor promoter TPA on the underlying skeletal framework, which is involved in the maintenance of both cell and epithelial tissue morphology. It should be emphasized, however, that similar results are obtained for all the tumor promoters as well as for the complete, ultimate carcinogens examined so far. The organization of the cytoskeletal elements involved in these morphological changes is faithfully retained during the fractionation procedure employed here, as is evident from SEM and TEM analysis of Triton-extracted cells. A number of promoting agents have been compared, and the degree of disorganization viewed in these whole mounts appears to parallel the potency of the promoting agents as measured by other assays (Fey and Penman, 1984). Also, the inactive analogues of phorbol ester have no effect on cell structure (Rifkin et al., 1979; Ojakian, 1981; Fey and Penman, 1984). We suggest that the effect of TPA on the cytoskeleton occurs early as compared with many of the commonly studied biochemical responses and may indeed underlie many of the previously described cellular response to promoting agents, such as mitogenic stimulation. TPA-induced alterations in NM-IF scaffold occur in the absence of both protein and RNA synthesis (Fey and Penman, 1984). By contrast, plasminogen activator, stimulated by TPA (Wigler and Weinstein, 1976), is completely blocked by pretreatment with both cycloheximide and actinomycin D (Weinstein et al., 1977; Ojakian, 1981). Ornithine decarboxylase, another enzyme that is rapidly induced by tumor promoters, is inhibited by both cycloheximide and actinomycin D in the presence of TPA (O'Brien, 1976). Thus two of the early biochemical markers for tumor-promoter activity are separable from the induction of cytoskeletal alterations by TPA. One of the most striking features of the response to promoting agents is the adoption of the transformed phenotype, in which cells lose growth control and cease being organized into meaningful tissue structure. The alteration of desmosomal and junctional associations and the concomitant change in cytokeratin organization are clearly related to the breakdown of epithelial organization. The phenotype is completely reversible although it takes about 3 days for the mode line to reestablish normal morphology (data not shown).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The morphological oncogenic signature. Reorganization of epithelial cytoarchitecture and metabolic regulation by tumor promoters and by transformation. 307 72

Tautomycin isolated from Streptomyces spiroverticillatus is an inhibitor of protein phosphatases 1 and 2A. Tautomycin induced hyperphosphorylation of cytokeratin peptides in human keratinocytes (PHK 16-I cells) 30 times less strongly than did okadaic acid. Repeated applications of tautomycin (30 micrograms, 40 nmol/application) did not induce tumor promotion in a two-stage carcinogenesis experiment on mouse skin initiated with 7,12-dimethylbenz[a]anthracene, whereas okadaic acid (1 microgram, 1.2 nmol/application) as a control induced tumor promotion strongly. As for mucosa of rat glandular stomach, tautomycin induced ornithine decarboxylase 4 h after intubation into the stomach. The tumor-promoting activity of tautomycin was next studied in the glandular stomach initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Administration of tautomycin in the diet (1 mg rat-1 day-1), from week 9 to week 52 of the experiment, inhibited rather than enhanced tumor development in the glandular stomach initiated with MNNG. The percentages of tumor-bearing rats of the groups treated with MNNG plus tautomycin, MNNG alone, and tautomycin alone were 20.0%, 40.6%, and 0% respectively in week 52. The reason for the absence of tumor-promoting activity of tautomycin was studied in relation to tumor necrosis factor alpha (TNF alpha), an endogenous tumor promoter. We found that tautomycin neither enhanced TNF alpha mRNA expression in mouse skin nor induced TNF alpha release in a human stomach cancer cell line (KATO III cells), whereas okadaic acid did both. These results indicate that not all inhibitors of protein phosphatases are tumor promoters, and suggest that tumor promotion of the okadaic acid class of compounds is mediated by TNF alpha.
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PMID:Tautomycin: an inhibitor of protein phosphatases 1 and 2A but not a tumor promoter on mouse skin and in rat glandular stomach. 755 47

Indole-3-carbinol (I3C) was examined for its ability to inhibit aflatoxin B1 (AFB1)-induced hepatocarcinogenesis in male Fischer rats when administered either before or after the carcinogen. After 13 weeks, animals pretreated with I3C (0.5% in the diet) for 2 weeks prior to administration of AFB1 and with continuing treatment during exposure to the carcinogen were protected from development of preneoplastic lesions, as determined by the classical markers gamma-glutamyltranspeptidase (GGT) and glutathione S-transferase (GST) P. In animals receiving AFB1 for 6 weeks before treatment with I3C, there was no obvious protective effect at 13 weeks compared with animals receiving only AFB1. Using cytokeratin 18 expression as a marker, animals fed AFB1 alone had a small number of positive foci at 13 weeks. However, no cytokeratin-positive foci were visible in the majority of livers from either group receiving I3C in combination with AFB1 and after 43 weeks all animals in these groups were protected from liver tumour formation. These results suggest that expression of cytokeratin 18, a later phenotypic change in foci than induction of GST-P and GGT, correlates more closely with tumour outcome in this model. I3C appeared to retard progression of AFB1-induced carcinogenesis at both the initiation and promotion stages. Continuous treatment with I3C for 13 weeks caused significant induction of CYP1A1, 1A2, 3A and 2B1/2, GST Yc2, aflatoxin B1 aldehyde reductase and quinone reductase. Such alteration of the drug metabolizing capacity of the liver by I3C contributes to blocking of initiation, while the observed inhibition of ornithine decarboxylase, a rate limiting enzyme in polyamine biosynthesis, and of tyrosine kinase activity may contribute to the suppressive effect of I3C.
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PMID:Chemoprevention of aflatoxin B1-induced carcinogenesis by indole-3-carbinol in rat liver--predicting the outcome using early biomarkers. 980 66