Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor cells release intact portions of their plasma membranes in the process of membrane fragment shedding. This released material has been shown to inhibit various synthetic functions of normal cells, which may play an important role in certain patho-physiological events occurring in advanced-stage cancer patients. Our studies on metastatic variants of the murine B16 melanoma, B16-F1 (low incidence of lung colonization) and B16-F10 (high incidence of lung colonization) indicate that the shed membrane fragment material is composed predominantly of vesicles, ranging in size from 20 to 100 nm in diameter. The release of membrane fragments represents a small percentage (approximately 16%) of the total shedding of plasma membrane components. Membrane fragments were shed at a higher rate from the highly "metastatic" (colonizing) B16-F10 cells than from poorly metastatic B16-F1 cells, resulting in a 2-fold greater accumulation of membrane fragment material by cultures of B16-F10 cells than by B16-F1 cultures during the 48-hr assay period. The study of various intracellu ar metabolic processes (protein and RNA synthesis, glycosylation, and generation of ATP) required for the shedding of membrane fragments indicated that the shedding event is only dependent on energy when inhibitors of the above processes are present for 2 hr. Treatment of cells with these inhibitors for 8 hr results in cessation of the shedding process, indicating both a limited pool of components to be shed and the requirement for further synthesis of the shed material. Glycoprotein components of the shed membrane fragments were analyzed by SDS-polyacrylamide gel electrophoresis. In addition to quantitative differences, 2 additional bands were present in fluorographs from SDS-PAGE gels from the B16-F10 membrane fragment material which were not present in fluorographs from B16-F1 fragments. The glycoprotein components of shed membrane fragments were shown to represent selected domains of the cell's plasma membranes, in that only certain plasma membrane glycoproteins are shed as part of membrane fragments. The glycoproteins released as non-particulate molecules into the extracellular environment failed to exhibit these quantitative and qualitative differences.
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PMID:Characterization of plasma membrane shedding from murine melanoma cells. 335 93

External ATP causes a marked increase in the passive permeability to phosphorylated metabolites in several types of transformed cells in alkaline medium containing low concentrations of Ca2+, but not in untransformed cells. Such increased membrane permeability with external ATP was also observed in B16 melanoma cells at pH 7.4-7.5 in both Tris-buffered saline and a growth medium containing 10% calf serum and divalent ions at normal concentrations, although a higher concentration of ATP was required. The permeability change in the growth medium was significantly enhanced by calmodulin-interacting drugs, such as trifluoperazine (TFP), N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) and chlorpromazine (CPZ). As expected, prolonged exposure of the cells to ATP in the serum-containing medium led to cell lysis. This ATP-dependent cell lysis was observed only in several transformed cell lines, and not in untransformed mouse fibroblasts. These results indicate that the effect of ATP on the membrane permeability in transformed cells is elicited under the physiological conditions and this would be useful in some limited way for cancer chemotherapy management.
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PMID:External ATP-induced passive permeability change and cell lysis of cultured transformed cells: action in serum-containing growth media. 338 48

The biochemical and biophysical roles of extracellular calcium ions in HVJ (Sendai virus)-induced cell fusion were studied. (1) Various kinds of cell, such as Ehrlich ascites tumor cells, mouse melanoma cells (B16-CW1 cells) and human epidermoid carcinoma cells (KB cells), could fuse in Ca2+-free medium containing a cheletor, glycoletherdiaminetetraacetic acid, in the same way as in Ca2+-containing medium. (2) The ATP content in Ehrlich ascites tumor cells decreased rapidly when the cells were treated with the virus in Ca2+-free medium but not in Ca2+-containing medium. (3) Intracellular adenine nucleotides leaked out into the reaction medium when the cells were treated with the virus in Ca2+-free medium but not in Ca2+-containing medium. (4) On addition of the virus, O2 consumption of Ehrlich ascites tumor cells decreased in Ca2+-free medium, but not in Ca2+-containing medium. (5) HVJ (Sendai virus) did not affect production of lactate by Ehrlich ascites tumor cells in both Ca2+-free medium and Ca2+-containing medium. These observations suggest that the role of extracellular Ca2+ in virus-induced cell fusion is to maintain the ATP and other intracellular metabolite contents at normal levels instead of triggering the fusion reaction itself.
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PMID:The role of extracellular calcium ions in HVJ (Sendai virus)-induced cell fusion. 625 May 92

Two partially purified fractions of the ethanol precipitate (70-95%) of the water extract of Harding-Passey mouse melanoma, which inhibit protein and DNA syntheses of B-16 melanoma cells in culture, also inhibit protein synthesis in various cell-free systems. By examining their inhibitory effects on limited reactions of protein synthesis, it was found that one of them (ME II) inhibits protein synthesis by blocking aminoacyl-tRNA formation, while the other (ME IV) does not. This inhibition of aminoacyl-tRNA formation was not limited to specific amino acids. Since the amino acid-dependent pyrophosphate (PPi)-ATP exchange reaction catalyzed by aminoacyl-tRNA synthetases was not inhibited, it was concluded that some factor(s) in ME II inhibits amino acid transfer from aminoacyl-AMP to tRNA. ME II contains more than 20 proteins from 10,000 to 90,000 daltons. EDTA treatment of this fraction caused the release of low-molecular substances with inhibitory activity from the proteins. The molecular weights of the active substances are less than 5,000 daltons. The active low-molecular substances are apparently not peptides or nucleotides.
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PMID:Inhibition of aminoacyl-transfer RNA formation by low-molecular substances from melanoma extract. 632 50

The insulin receptor possesses an insulin-stimulated tyrosine-kinase activity; however, the significance of receptor phosphorylation in terms of the binding and signaling function of the receptor is unclear. To help clarify this problem, we have studied insulin binding and receptor phosphorylation in a Cloudman S91 melanoma cell line and two of its variants: the wild type (1A) in which insulin inhibits cell growth, an insulin-resistant variant (111) in which insulin neither stimulates or inhibits growth, and a variant (46) in which insulin stimulates cell growth. 125I-insulin binding to intact cells was similar for the wild-type 1A and insulin-stimulated variant 46. The insulin-resistant variant 111, in contrast, showed approximately 30% decrease in insulin binding. This was due to a decrease of receptor affinity with no major difference in receptor number. When the melanoma cells were solubilized in 1% Triton X-100 and the insulin receptor was partially purified by chromatography on wheat germ agglutinin-agarose, a similar pattern of binding was observed. Phosphorylation was studied by incubation of the partially purified receptor with insulin and [gamma-32P]ATP, and the receptor was identified by immunoprecipitation and NaDodSO4 PAGE. Insulin stimulated phosphorylation of the 95,000-mol-wt beta-subunit of the receptor in all three cells types with similar kinetics. The amount of 32P incorporated into the beta-subunit in the insulin-resistant cell line 111 was approximately 50% of that observed with the two other cell lines. This difference was reflected throughout the entire dose-response curve (10(-9) M to 10(-6) M). Qualitatively similar results were obtained when phosphorylation was studied in the intact cell. Peptide mapping of the beta-subunit using tryptic digestion and reverse-phase high-performance liquid chromatography column separation indicated three sites of phosphorylation in receptor from the wild type and variant 46, but only two major sites of phosphorylation of variant 111. These data suggest that the insulin-resistant variant melanoma 111 possesses a specific defect in the insulin receptor which alters both its binding and autophosphorylation properties, and also suggests a possible role of receptor phosphorylation in both the binding and the signaling function of the insulin receptor.
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PMID:Abnormality of insulin binding and receptor phosphorylation in an insulin-resistant melanoma cell line. 638 9

The activities of glycogen synthase and phosphorylase were measured and compared to the growth-related variations of glycogen accumulation in three cultured human tumor cell lines: HT-29 (colon carcinoma); MeWo (malignant melanoma); and RT-4 (carcinoma of the urinary bladder). A similar pattern of variations in the enzyme activities was found in the three cell lines. The activities of the a + b forms of glycogen phosphorylase increased throughout the culture period. Maximal activity of phosphorylase a coincided with low intracellular concentrations of glycogen during the period of exponential growth. When the rate of cell division decreased, phosphorylase a activity also decreased while the glycogen levels increased. Glycogen synthase was almost entirely in b form during the entire culture period, i.e., in both the exponential and the stationary phases. In vitro incubation of the cellular extracts without NaF showed, however, that the enzyme could be partially converted to the a form by the endogenous phosphatases. The A0.5 values of the enzyme for glucose-6-phosphate (Glc-6-P) were of the same order of magnitude as the intracellular Glc-6-P concentrations which ranged from 2.2 to 5.4 mM (almost 10 times those reported in normal cells). Similar Glc-6-P values were obtained by two different extraction methods controlled by the intracellular ATP and ADP concentrations. The Km values for uridine-5'-diphosphoglucose were always 2 to 3 times lower than the intracellular uridine-5'-diphosphoglucose concentrations. These results suggest that: (a) in these tumor cells, glycogen is essentially synthesized by glycogen synthase b via an allosteric activation by intracellular Glc-6-P; (b) there is no obvious growth-related control of glycogen synthase activity; and (c) the activity of glycogen phosphorylase seems to be growth dependent with maximal phosphorylase a activities associated with the period of high division rate.
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PMID:Growth-related enzymatic control of glycogen metabolism in cultured human tumor cells. 641 76

We have previously reported [(1980) J. Biol. Chem. 255, 5999-6002] that retinoic acid inhibited growth and increased cyclic-AMP-dependent protein kinase activity in mouse melanoma cells. A variant melanoma line having depressed levels of cyclic-AMP-dependent protein kinase was not growth-inhibited by retinoic acid. In this report we describe the effect of retinoic acid on cyclic AMP binding proteins in B16 mouse melanoma cells. Using the technique of photoaffinity labeling, we found three major proteins of Mr 49 000, 52 000, and 55 000 which were specifically labeled with 8-N3-[32P]AMP in both control and treated cells. Based upon their molecular weight, relative affinity for 8-N3-[32P]AMP and comigration with standards, we have designated the 49 000-Mr and 55 000-Mr species as RI and RII respectively. The position of the intermediate band (Mr 52 000) was not affected by pre-incubation with ATP or alkaline phosphatase, and two-dimensional gel analysis indicated that it had the same pI as RI. Retinoic acid increased the 8-N3-[32P]AMP labeling of RI within 24 h, reaching a maximal six fold increase by 48 h. These increases were limited to the 40 000 X g supernatant fraction and occurred prior to any growth inhibition. By using increasing concentrations of 8-N3-cAMP we were able to construct a saturation curve for RI binding. Calculation of apparent Kd values from these curves showed nearly identical affinities for RI binding of 8-N3-cAMP from control and retinoic-acid-treated cells. Therefore we conclude that retinoic acid is increasing the amount of RI rather than altering its properties. Corroboration of these results was obtained by DEAE-cellulose chromatography. Peak I (corresponding to type I protein kinase) from retinoid-treated cells was increased about six fold in binding activity.
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PMID:The effect of retinoic acid on cyclic-AMP-binding proteins in mouse melanoma cells. 669 18

A two-step procedure for releasing cells from solid tumors has been applied to specimens of human melanoma, sarcoma, lung, colon, and breast carcinoma. The first population released mechanically has been compared with the population subsequently released enzymatically in tests of dye exclusion, ribonucleoside triphosphate pool sizes, intactness of DNA, and clonogenicity in soft agar. While greater numbers of dye-excluding cells are released in the enzymatic step, and these cells have higher ribonucleoside triphosphate pools and more intact DNA, both populations contain clonogenic cells in approximately equal numbers. Several semisolid media were employed in tests of clonogenicity, and all methods employing an agar underlayer appeared satisfactory and approximately equivalent in cloning efficiency. The methyl cellulose upper layer system facilitated implanting of pooled colonies into nude mice, which resulted in growth in the nude host and marked increase in cloning efficiency when the cells were replanted into soft agar-methyl cellulose plates. A comparison of four different areas of individual tumor specimens was made with cells released enzymatically and measuring cell yield, dye exclusion, ATP pool size, and uptake and metabolism of 5-fluoropyrimidines. Only relatively small variations were seen from one area to the next, with trypan blue exclusion exhibiting the least variation, and metabolism of fluorinated pyrimidines showing the most.
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PMID:The soft agar clonogenicity and characterization of cells obtained from human solid tumors by mechanical and enzymatic means. 703 39

We have examined properties of glucocorticoid-receptor complexes which might account for dexamethasone induced alterations in the growth and morphology of melanoma target cells. We have used cultured cells and solid tumors derived from the dexamethasone-sensitive RPMI 3460 Syrian hamster melanoma cell line together with clonal variants which are either more sensitive (clone 6) or resistant (clone 5) to the growth inhibiting effects of dexamethasone. Although differing markedly in their response to corticoids, each of the cell lines contains significant quantities of glucocorticoid receptor. The present studies were designed to determine if differences in the transformability (nuclear binding ability) of the glucocorticoid receptors from these target cells could account for their sensitivity or resistance to glucocorticoids. Cytosolic glucocorticoid-receptor complexes were analyzed by DEAE-cellulose chromatography to identify and quantitate the relative amounts of native (unactivated) and transformed (activated-nuclear binding) receptors present. We could readily separate these two major forms of the glucocorticoid-receptor complex in cytosols from each of the melanoma cell lines and solid tumors examined. The identity of these receptor complexes as native or transformed was confirmed using both ATP-agarose and isolated nuclei; only transformed receptor complexes are bound. When cytosol is prepared in the presence of 10 mM sodium molybdate, only native receptor is present. After molybdate is removed, native glucocorticoid receptor is readily transformed by increased ionic strength. We conclude that resistance to dexamethasone-induced changes in growth observed in resistant clone 5 cells and solid tumors cannot be attributed to an inability of the receptor they contain to exist as a stable, transformed complex.
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PMID:Identification of transformed glucocorticoid receptor from dexamethasone resistant melanoma. 710 74

External ATP causes a passive permeability change in several transformed cells but not in untransformed mouse fibroblasts. In the present experiments, the ATP-specific permeability change was observed also in B16 melanoma and L929 cells. The sensitivity to external ATP of these cells increased further when the concentration of intracellular ATP was lowered by addition of a mitochondrial inhibitor. In contrast, mouse 3T3 cells transformed by murine sarcoma virus did not respond to external ATP even when the intracellular ATP was depleted. Such differences in the ATP-sensitivity were not ascribed to the different concentrations of intracellular ATP.
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PMID:Different sensitivities to external ATP in passive permeability of transformed mouse cell lines. 716 38


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