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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extravasal fibrin deposition is frequently observed within and around tumorous tissues and has been implicated in various aspects of tumor growth. However, no adequate information has been available on the mechanism how intratumoral interstitial fibrin deposits escape a prompt elimination by the fibrinolytic system. In this study we provide immunomorphological evidence showing that fibrin deposits in lymph nodes with Hodgkin's disease are stabilized and made resistant to fibrinolysis by factor XIII (FXIII) of blood coagulation. By double immunofluorescent labelling systems fibrin deposits were simultaneously stained for alpha 2-antiplasmin (alpha 2-AP), the main physiological inhibitor of fibrinolysis and in a number of nodular areas they were also labelled for plasmin(ogen). The detection of alpha 2-antiplasmin-plasmin complex-neoantigen (alpha 2-AP-P-Neo) revealed that alpha 2-AP reacted with plasmin, i.e., alpha 2-AP covalently linked to fibrin indeed inhibited intratumoral fibrinolysis. In addition to fibrin deposits FXIII was also found in cellular elements characterized earlier as tumor associated macrophages. These cells were attached to fibrin strands suggesting that they are involved in the intratumoral fibrin formation and might be a source of fibrin stabilizing factor in the tumor stroma.
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PMID:Fibrinolysis resistant fibrin deposits in lymph nodes with Hodgkin's disease. 306 59

We have shown that retinoic acid, applied either to the skin or administered in diet, inhibits skin tumor promotion by TPA. Retinoic acid does not inhibit the initiation step of mouse skin carcinogenesis. Our results indicate that retinoic acid inhibits both stage I and stage II of tumor promotion, and the inhibition of tumor promotion depends upon the duration of retinoic acid treatment. The inhibition of skin carcinogenesis by retinoic acid is not universal; retinoids exhibit specificity towards carcinogens and tumor promoters. In conclusion, the results presented indicate that the inhibition of TPA-induced ODC gene expression may be one of the mechanisms contributing to the antitumor promoting property of the retinoids. However, other mechanisms concerning the effect of retinoic acid on chromatin structure (Porter et al., 1986), glycoprotein synthesis (Levin et al., 1983), peptide growth factors (Sporn et al., 1986), induction of transglutaminase (Lichti and Yuspa, 1985) and the host-immune system (Dennert, 1985) may also explain the molecular basis of retinoid action.
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PMID:Inhibition of phorbol ester-induced ornithine decarboxylase gene transcription by retinoic acid: a possible mechanism of antitumor promoting activity of retinoids. 328 48

Interaction of tumor promoting phorbol esters with specific high affinity receptors is probably essential for many of the biological responses elicited by these agents. Since diacylglycerols which can be produced enzymatically from phospholipids by phospholipase C are postulated to be the physiological ligands for the phorbol ester receptor, we have examined primary cultures of mouse epidermal basal cells exposed to phospholipase C (Clostridium perfringens) for several biological and biochemical responses characteristic of treatment with 12-O-tetradecanoyl-phorbol-13-acetate, the most potent phorbol ester tumor promoter. Formation of diacylglycerols by treatment with phospholipase C was demonstrated by the dose-dependent release of radioactive diacylglycerols in cells prelabeled with [3H]arachidonic acid. Treatment with phospholipase C at 0.05 units/ml for 30 min led to the morphological changes and to the reduction in epidermal growth factor binding (90%) associated with 12-O-tetradecanoylphorbol-13-acetate treatment. Continuous treatment at the same dose led to the induction of the enzymes ornithine decarboxylase and transglutaminase with a time course and extent similar to the inductions by 12-O-tetradecanoylphorbol-13-acetate. Treatment with phospholipase C at 0.1 enzyme unit/ml yielded substantial suppression of the binding affinity of phorbol-12,13-dibutyrate for its receptors without reduction in total number of binding sites, consistent with the production by phospholipase C of a competitive inhibitor of phorbol ester binding. Several diacylglycerols at concentrations of 250 microM and above effectively competed for phorbol-12,13-dibutyrate binding, reduced epidermal growth factor binding, and to a lesser extent induced ornithine decarboxylase and transglutaminase. These results support the hypothesis that diacylglycerols can act through the phorbol ester receptors and thus produce biological and biochemical responses similar to those of the phorbol esters.
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PMID:Similar effects of phospholipase C and phorbol ester tumor promoters on primary mouse epidermal cells. 393 7

The relative cytotoxic sensitivity of the YPC-1 tumor target cells from untreated mice and from animals treated with nitrosoureas was determined. The amount of 51Cr released from target cells increased significantly when the cells were obtained from treated mice. On the basis of the results of cold-target cytotoxicity inhibition assay, this enhancement was shown to be haplotype specific. The amount of 51Cr released from target cells of mice treated with N,N'-bis(chloroethyl)-N-nitrosourea decreased significantly when the tumor cells were first incubated with fibrinogen and transglutaminase. Based on these results and other published data, a model system is suggested. The model is based on the observation that tumors, and thus tumor antigens, at the cell surface are partly or completely covered by fibrinogen or fibrin. The enzyme transglutaminase is involved in the binding of the fibrinogen or fibrin to the cell surface. Accordingly, it is hypothesized that the nitrosoureas have a dual mode of immunotherapeutic activity. The carbamoylating properties inhibit the fibrin-binding activity of transglutaminase, thus preventing fibrin from covering up or coating the tumor cells and preventing the ability of sensitized effector cells to recognize the tumor-specific antigens in association with self H-2 antigens. The alkylating property of the nitrosoureas mainly concerns reactivity with the DNA of the tumor cells.
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PMID:Increased cytotoxic sensitivity of YPC-1 tumor cells from mice treated with nitrosoureas. 611 91

Pretreatment of primary mouse epidermal cell cultures with chymostatin, a protease inhibitor, blocked the increase in transglutaminase (R-glutaminyl-peptide:amine gamma-glutamyltransferase, EC 2.3.2.13) activity resulting from treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) or with retinoic acid. This inhibitory effect was dependent upon both the concentration of chymostatin used and preincubation time and was eliminated when chymostatin was inactivated by NaBH4 reduction. Five other protease inhibitors, antipain, leupeptin, pepstatin, aprotinin, and soybean trypsin inhibitor, also suppressed TPA induction of transglutaminase activity. However, neither chymostatin, nor antipain, nor leupeptin reduced protein synthesis as measured by incorporation of labeled leucine into acid-precipitable products, while pepstatin, aprotinin, and soybean trypsin inhibitor inhibited protein synthesis markedly. L-1-Tosylamide-2-phenylethylchloromethyl ketone, on the other hand, strongly inhibited protein synthesis but did not inhibit the increase of transglutaminase activity after TPA exposure, and elastatinal inhibited neither TPA action nor protein synthesis. Chymostatin did not block phorbol ester binding to epidermal cells or TPA-mediated reduction of epidermal growth factor binding. These results suggest that the apparent induction of intracellular transglutaminase activity is mediated by a chymostatin-sensitive protease, while both phorbol ester binding and the reduction by TPA of epidermal growth factor binding at the cell membrane were independent.
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PMID:Inhibition of 12-O-tetradecanoylphorbol-13-acetate induction of epidermal transglutaminase activity by protease inhibitors. 613 3

Transglutaminase may be an important intracellular regulator of protein function through its ability to catalyze the calcium-dependent covalent linkage of primary amines to glutamine residues in peptide linkage with the generation of ammonia. This study provides further evidence that a major alteration in tumor cells is the marked decline in the expression of transglutaminase activity. This may alter its known protein cross-linking activity and favor lack of differentiation and proliferation.
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PMID:Transglutaminase activity in Yoshida ascites tumor cells. 613 87

A number of characteristics of phorbol ester-mediated mouse skin tumor promotion indicate that cell selection is the underlying biological process. Studies in vivo and in cultured mouse epidermal cells suggest that selection is based on heterogeneous responses of subpopulations of basal cells which can be induced to proliferate or differentiate in response to promoter exposure. Retinoids are effective inhibitors of tumor promotion in mouse skin but do not influence the proliferative response to phorbol esters. Since both retinoids and phorbol esters modify epidermal differentiation, the antipromoter action of retinoids could be related to differentiation responses. Retinoic acid induces transglutaminase activity in cultured mouse epidermal basal cells grown in less than 0.1 mM Ca2+. While this enzyme is associated with terminal differentiation in skin, retinoic acid paradoxically blocks the terminal differentiation of cultured cells. In contrast, phorbol esters and extracellular calcium greater than 0.1 mM induce both transglutaminase activity and terminal differentiation. Enzyme kinetic analyses indicate that the transglutaminases induced by all three inducers are the same enzyme. The increase in activity of transglutaminase by all three inducers requires RNA and protein synthesis. However, the time course of increase and decay of each activity differs for each inducer. A variety of biologically active retinoids induce transglutaminase activity, and their effectiveness correlates with their reported antipromoter activity. Exposures to both retinoic acid and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate are antagonistic resulting in less than additive induction. Induction kinetics with both inducers are more like those of retinoic acid than those of the phorbol ester. Simultaneous exposure to retinoic acid and 12-O-tetradecanoylphorbol-13-acetate protects the epidermal cell population from induced terminal differentiation and cell loss which is observed in response to the promoter alone. These results suggest that the antipromoting action of retinoids could be mediated by modification of phorbol ester-accelerated terminal differentiation through an effect on transglutaminase and cornification. This action of retinoids would block a critical aspect of cell selection involving loss of cells and subsequent regenerative hyperplasia, although simple hyperplasia may still occur.
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PMID:Regulation of epidermal transglutaminase activity and terminal differentiation by retinoids and phorbol esters. 613 62

Eight cell lines exhibiting resistance to Ca2+ induced terminal differentiation were derived from primary mouse epidermal cultures and their properties analyzed. The lines developed either spontaneously (2 lines) or after exposure of primary cultures to carcinogens or carcinogens and tumor promoter. All but one of the lines were of epithelial or epitheloid morphology but 3 of the 8 lines lacked desmosomes, keratin filaments and immunoprecipitable keratin proteins, and thus could not be defined as keratinocytes. Two of the 5 keratinocyte lines were tumorigenic in syngeneic Balb/c newborns after 4 months in medium containing 1.2 mM Ca2+, and 3 lines remained non-tumorigenic even after 11 months in 1.2 mM Ca2+. All three of the non-keratinizing lines were tumorigenic. Tumorigenic potential of the 5 keratinocyte lines did not correlate with ploidy (as determined by DNA content), transglutaminase activity or growth in soft agar. However, the 2 tumorigenic keratinocyte lines contained cells which stained intensely red for gamma glutamyl transpeptidase activity, while the non-tumorigenic keratinocyte lines did not. Only those lines lacking desmosomes and keratin filaments grew in soft agar, but these lines were negative for gamma glutamyl transpeptidase activity. Ploidy and transglutaminase activity did not correlate with tumorigenicity in these non-keratinizing lines. These results show that cell lines derived from cultured mouse epidermal cells and selected on the basis of their resistance to Ca2+ induced terminal differentiation may be preneoplastic. Furthermore the association of additional markers with malignant change in these cell lines depended on whether or not the cells were keratinizing.
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PMID:Properties of carcinogen altered mouse epidermal cells resistant to calcium-induced terminal differentiation. 619 37

PMNs upon stimulation by a chemoattractant adhere to a substratum and then in amoeboid fashion migrate toward the source of the attractant. We have studied molecular events in both adherence and migration and have arrived at the following conclusions: 1) PMNs, like other motile cells such as highly metastatic tumor cells, can use laminin to attach to Type IV basement membrane collagen. PMNs may use this anchoring mechanism in their emigration from the vasculature. 2) Attached cells may be stimulated to migrate as a result of the chemo-attractant-induced inactivation of lipomodulin, a natural inhibitor of phospholipase A2, an enzyme that may be essential for chemotaxis. 3) The substrate for this enzyme is generated by both the CDP-choline and transmethylation pathways. These pathways may be regulated by another enzyme, transglutaminase (TGase). 4) Natural substrates of TGase, such as uteroglobin, inhibit leukocyte chemotaxis, again suggesting a regulatory role for TGase in chemotaxis. 5) Tumor cells also produce inhibitors of chemotaxis. In addition to protecting the tumor from the host's phagocytes, these inhibitors may be related to normal modulators of cell motility. Therefore, determination of their mode of action could increase our understanding of this type of cell behavior.
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PMID:Adherence and regulation of leukotaxis. 657 14

Mouse epidermal basal cells can be selectively cultivated in medium with a calcium concentration of 0.01--9.09 mM. Terminal differentiation and sloughing of mature keratinocytes occur when the calcium concentration is increased to 1.2--1.4 mM. When basal cell cultures are exposed to chemical initiators of carcinogenesis, colonies of cells that resist calcium-induced differentiation evolve. Likewise, basal cells derived from mouse skin initiated in vivo yield foci that resist terminal differentiation. This defect in the commitment to terminal differentiation appears to be an essential change in initiated cells in skin and is also characteristic of malignant epidermal cells. This model system has also provided a means to determine if basal cells are more responsive to phorbol esters than other cells in epidermis and to explore the possibility that heterogeneity of response exists within subpopulations of basal cells. The induction of the enzyme ornithine decarboxylase (ODC) was used as a marker for responsiveness to phorbol esters. ODC induction after exposure to 12-0-tetradecanoylphorbol-13-acetate (TPA) in basal cells is enhanced 20-fold over the response of a culture population containing both differentiating and basal cells. When basal cells are induced to differentiate by increased calcium, responsiveness to TPA is lost within several hours. In basal cell cultures, two ODC responses can be distinguished. After exposure to low concentrations of TPA or to weak promoters of the phorbol ester series, ODC activity is maximal at 3 hr. With higher concentrations of TPA, the ODC maximum is at 9 hr. These results are consistent with the presence of subpopulations of basal cells with differing sensitivities to TPA. Other studies that use the enzyme epidermal transglutaminase as a marker for differentiation support this conclusion. In basal cell culture TPA exposure rapidly increases transglutaminase activity and cornified envelope development, reflecting induced differentiation in some cells. As differentiated cells are sloughed from the dish, the remaining basal cells proliferate and become resistant to induced differentiation by 1.2 mM calcium. These data provide additional evidence of basal cell heterogeneity in which TPA induces one subpopulation to differentiate while another is stimulated to proliferate and resists a differentiation signal. Tumor promoters, by their ability to produce heterogeneous responses with regard to terminal differentiation and proliferation, would cause redistribution of subpopulations of epidermal cells in skin. Cells that resist signals for terminal differentiation, such as initiated cells, would be expected to increase in number during remodeling, Clonal expansion of the initiated population could result in a benign tumor with an altered program of differentiation. In skin, benign tumors are the principal product of 2-stage carcinogenesis. Subsequent progression to malignancy may involve an additional step, probably a genetic alteration, that is independent of the tumor promoter.
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PMID:Initiator and promoter induced specific changes in epidermal function and biological potential. 732 73


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