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

Human melanoma cells secret a 21-kDa protein, termed CSC-21K, which binds with 1:1 molar stoichiometry to the matrix metalloproteinase type IV collagenase proenzyme (70-kDa gelatinase) secreted by the same cells. This binding protein has been purified and its complete primary structure determined by sequencing overlapping peptides which span the entire protein. The amino acid sequence demonstrates that this protein shares significant homology with human TIMP (tissue inhibitor of metalloproteinase), including conservation of the positions of the 12 cysteine residues and 3 of 4 tryptophan residues. The identification of CSC-21K now indicates that a family of TIMP-related proteins exists. Individual members of this family may possess selective affinities for different members of the matrix metalloproteinase family. CSC-21K produced by tumor cells is isolated as a 1:1 molar complex with type IV procollagenase, as demonstrated by amino acid composition analysis. Addition of purified CSC-21K to the activated metalloproteinase results in inhibition of the collagenolytic activity in a stoichiometric fashion. Based on its sequence homology to TIMP and ability to inhibit type IV collagenolysis we propose the name TIMP-2 for this inhibitor.
 ...
PMID:Tissue inhibitor of metalloproteinase (TIMP-2). A new member of the metalloproteinase inhibitor family. 279 61

Activities of a cathepsin B-like cysteine proteinase have previously been observed to correlate with the malignancy of several animal and human tumors. Plasma membrane fractions of some of these tumors have been found to be enriched in cathepsin B-like activity. We have determined the subcellular distribution of this enzyme and three additional lysosomal hydrolases (cathepsin H, beta-hexosaminidase, and beta-glucuronidase) in normal murine liver and six metastatic variants of the B16 melanoma. The tissues were fractionated initially by differential centrifugation followed by Percoll density gradient centrifugation of the light mitochondrial fraction. Two fractions were obtained: an L-2 fraction enriched in all four lysosomal hydrolases; and an L-1 fraction enriched in a marker enzyme for the plasma membrane. Cathepsin B-like and beta-hexosaminidase activities, but not the other hydrolase activities, were also found to be enriched in the L-1 fractions of the metastatic B16 tumors. We explored the nature of the association of the cathepsin B-like activity with the plasma membrane using fractions from the spontaneously metastatic B16 amelanotic melanoma. Activity could not be dissociated from the plasma membrane fraction by washing with a physiological salt solution suggesting that it was not adsorbed to this fraction nonspecifically, nor could it be displaced by mannose 6-phosphate or other sugars which compete for binding to the known lysosomal receptors. High salt concentrations, low concentrations of the mild detergent saponin, mild acidification, or phosphatidylinositol-specific phospholipase C did not elute the cathepsin B-like activity. However, activity was eluted by exposure to 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, a detergent used in the purification of integral membrane proteins. The B16 amelanotic melanoma plasma membrane-associated cathepsin B-like activity had a slightly higher pH optimum and was resistant to inactivation by neutral pH and to inhibition by three low molecular weight inhibitors of cysteine proteinases. The Ki values for inhibition by leupeptin and stefin A were 20-fold higher. The presence of a cathepsin B-like cysteine proteinase at the surface of metastatic tumor cells, particularly in a form which can retain activity at physiological pH and retain activity in the presence of extracellular proteinase inhibitors, may contribute to the focal dissolution of the extracellular matrix observed at sites of contact with invading tumor cells.
 ...
PMID:Properties of a plasma membrane-associated cathepsin B-like cysteine proteinase in metastatic B16 melanoma variants. 282 39

The effect of cysteine and glutathione on mammalian melanogenesis has been studied. It has been shown that their action is mediated by two different mechanisms. (a) The reaction of the thiol groups with dopaquinone after the tyrosinase-catalyzed oxidation of tyrosine and dopa. This mechanism leads to the formation of sulfhydryl-dopa conjugates and finally sulfur-containing pigments, phaeomelanins instead of eumelanins. This fact might produce an inhibition of melanogenesis due to the slower rate of chemical reactions involved in the polymerization of such thiol-conjugates when compared to that of indoles. (b) The direct interaction between the sulfhydryl compounds and the tyrosinase active site. This interaction may regulate the activity of the enzyme. It is shown that Harding-Passey mouse melanoma tyrosinase is more sensitive to sulfhydryl compounds than mushroom tyrosinase. Cysteine always produces an inhibition of the tyrosinase hydroxylase and dopa oxidase activities of melanoma tyrosinase, this inhibition becoming greater as the cysteine concentration increases. On the other hand, glutathione produces an activation of the tyrosine hydroxylase activity below 3 mM and an inhibition at higher concentrations. The limit between the enzymatic activation and inhibition appears at glutathione concentrations similar to the physiological levels of this compound found in melanocytes. Although the switch from eumelanogenesis to phaeomelanogenesis occurs at much lower concentrations of glutathione, taking into account these data it is discussed that this sulfhydryl compound may regulate not only the type but also the amount of melanin formed inside melanocytes.
 ...
PMID:The role of sulfhydryl compounds in mammalian melanogenesis: the effect of cysteine and glutathione upon tyrosinase and the intermediates of the pathway. 290 72

Monoclonal antibodies to the human nerve growth factor receptor have been used to biochemically characterize the receptor in the human melanoma cell line A875. Labeling of A875 cell proteins by culture with [35S]cysteine or labeling of cell surface proteins with 125I followed by immunoprecipitation with anti-nerve growth factor receptor antibody reveals a receptor protein with an apparent Mr of 70,000-75,000 and an isoelectric point of 4.9-5.2. Incorporation of [3H]glucosamine into this species indicates it is a glycoprotein. The receptor becomes phosphorylated on serine residues in intact cells and in isolated membranes incubated with [gamma-32P]ATP. The receptor appears to exist, at least partially, in the form of a disulfide-linked oligomer (probably a dimer) of Mr = 75,000 subunits. Kinetic [35S]cysteine labeling studies reveal an Mr = 59,000 core protein which is glycosylated via N-linked and probably also O-linked sugar moieties to produce the mature (Mr = 70,000-75,000) receptor.
 ...
PMID:Characterization of the human melanoma nerve growth factor receptor. 298 74

The tissue-destructive proteinases of B16-BL6 melanoma cells from C57BL/6 mice and subcellular fractions were examined. Cancer cell organelles were isolated following nitrogen cavitation with the use of sucrose density gradient centrifugation. Serine, cysteine, and metalloproteinases were assayed with the use of radiolabeled proteins and synthetic substrates. Tumor-induced red blood cell lysis was quantitated by measurement of the release of isotope from 59Fe-labeled red blood cells (RBC) cocultivated with melanoma cells; the RBC were from Wistar rats. Enzyme inhibitors with specificity toward different classes of proteinases were used in the above assays to categorize the enzymes responsible for substrate degradation. Results indicated that intact melanoma cells, cell organelles, and cytosol contain proteinases that can degrade collagen and gelatin and lyse normal RBC. Melanoma plasma membranes are highly enriched in collagenase, gelatinase, cysteine proteinase, plasminogen activator, and cytolytic activity. The inhibition of tumor collagenolytic, gelatinolytic, and cytolytic activities by EDTA and 1,10-phenanthroline but not by diisopropyl fluorophosphate and N alpha-p-tosyl-L-lysine chloromethyl ketone indicates that metalloproteinases are the active enzymes in these assays. Minocycline, a synthetic tetracycline with demonstrable inhibitory activity with other mammalian collagenases, also inhibited melanoma collagenolytic and cytolytic activities.
 ...
PMID:Diversity of melanoma plasma membrane proteinases: inhibition of collagenolytic and cytolytic activities by minocycline. 299 28

Human melanoma cells express relatively large amounts of the disialogangliosides GD3 and GD2 on their surface whereas neuroblastoma cells express GD2 as a major ganglioside. Monoclonal antibodies (Mabs) directed specifically to the carbohydrate moiety of GD3 and GD2 inhibit melanoma and neuroblastoma cell attachment to various substrate adhesive proteins, e.g. collagen, vitronectin, laminin, fibronectin, and a heptapeptide, glycyl-L-arginyl-glycyl-L-aspartyl-L-seryl-L-prolyl-L-cysteine, which constitutes the cell attachment site of fibronectin. Cells that are preattached to a fibronectin substrate can also be induced to detach and round up in the presence of purified anti-ganglioside Mab. Moreover, when melanoma cells that contain both GD2 and GD3 are incubated with Mabs directed to both of these molecules an additive inhibition is observed. The specificity of this inhibition is demonstrated since Mabs of various isotypes directed to either protein or carbohydrate epitopes on a number of other major melanoma or neuroblastoma cell surface antigens have no effect on cell attachment. A study of the kinetics involved in this inhibition indicates that significant effects occur during the first 5 min of cell attachment, suggesting an important role for GD2 and GD3 in the initial events of cell-substrate interactions. The role of gangliosides in cell attachment apparently does not directly involve a strong interaction with fibronectin since we could not observe any binding of radiolabeled fibronectin or fragments of the molecule known to contain the cell attachment site to melanoma gangliosides separated on thin-layer chromatograms. An alternative explanation would be that gangliosides may play a role in the electrostatic requirements for cell-substrate interactions. In this regard, controlled periodate oxidation of terminal, unsubstituted sialic acid residues on the cell surface not only specifically destroys the antigenic epitopes on GD2 and GD3 recognized by specific Mabs but also inhibits melanoma cell and neuroblastoma cell attachment. In fact, the periodate-induced ganglioside oxidation and the inhibition of cell attachment are equally dose dependent. These data suggest that cell-substratum interactions may depend in part on the electrostatic environment provided by terminal sialic acid residues of cell surface gangliosides and possibly other anionic glycoconjugates.
 ...
PMID:Disialogangliosides GD2 and GD3 are involved in the attachment of human melanoma and neuroblastoma cells to extracellular matrix proteins. 300 35

Trigramin, a cysteine-rich, RGD-containing peptide isolated from the venom of the Trimeresurus gramineus snake, inhibited the adhesion of human melanoma cells to fibronectin and fibrinogen. Compared on a molar basis to GRGDSP, trigramin was approximately 500 times more potent than the hexapeptide at inhibiting cell adhesion to fibronectin. The activity of trigramin was abolished by chemical reduction of the molecule, indicating that the secondary structure is important to the biological activity. Trigramin presents an example of an effective inhibitor of cell adhesion that has developed in nature and may prove to be a useful probe in studying the cell surface receptors involved in cell adhesion.
 ...
PMID:Trigramin, an RGD-containing peptide from snake venom, inhibits cell-substratum adhesion of human melanoma cells. 304 27

Peptide aldehyde transition state analogue inhibitors of serine and cysteine proteases have been used to selectively inhibit proteases for which prior evidence supports a role in tumor cell metastasis. These enzymes include cathepsin B, urokinase plasminogen activator (PA), and thrombin. The inhibition constants of the peptidyl aldehyde inhibitors show that they are highly selective for a particular targeted serine or cysteine protease. The inhibitors are introduced by i.p. injection or by miniosmotic pumps into syngeneic C57BL/6 mice also given injections of B16-F10 melanoma cells, and the number of metastatic foci in the lung was determined. While the injection protocol gave an initially high but changing in vivo concentration of inhibitor over time, the minipump implant gave a constant steady state concentration of inhibitor over 5-7 days. Minipump infusion of leupeptin (acetylleucylleucylargininal), a strong inhibitor of cathepsin B at a steady state plasma concentration 1000-fold greater than its Ki(cathepsin B), gave no significant decrease in lung colonization by the B16 tumor cells. Ep475, a stoichiometric irreversible peptide inhibitor of cathepsin B-like proteases, also did not significantly inhibit metastatic foci formation. Introduction of selective inhibitors of urokinase PA, tert-butyloxycarbonylglutamylglycyl-argininal and H-glutamylglycylargininal at concentrations near its Ki, produced no significant decrease in mouse lung colonization. The selective thrombin inhibitor D-phenylalanylprolylargininal infused to a steady state concentration 100-fold greater than its Ki dramatically increased B16 melanoma colonization of mouse lung. The results indicate that neither secreted cathepsin B-like nor urokinase PA have roles in B16 colonization of mouse lung, while thrombin may have a role in preventing metastasis. These experiments do not eliminate roles for a cathepsin B-like enzyme or urokinase PA in the initial steps of the metastatic process.
 ...
PMID:Selective inhibition of proteolytic enzymes in an in vivo mouse model for experimental metastasis. 308 87

Challenge of human or murine melanoma cells with sodium arsenite, heavy metals (Zn2+, Cu2+ and Cd2+), or thiol-reactive agents (p-chloromercuribenzoate and iodoacetamide) induced the synthesis of four stress proteins with molecular masses of 100, 90, 72 (a doublet), and 32 (human) or 34 (murine) kDa. Enhanced expression of the 32- and 34-kDa polypeptides (p32 and p34) preceded or paralleled the synthesis of the other stress proteins. Hyperthermia, the calcium ionophore A23187, and amino acid analogs (L-azetidine-2-carboxylic acid and L-canavanine) induced the formation of the major stress proteins, but failed to increase synthesis of p32 and p34. Characterization of the dose and time dependence of p32 and p34 synthesis in human (A375) and murine (B16-F10) melanoma cells, respectively, indicated that these proteins were subject to similar regulatory mechanisms. Electrophoretic analysis of stressed cells pulsed with different metabolic precursors revealed that p32 and p34 were radiolabeled with [35S]methionine or 3H-amino acids but not by [3H]mannose or [35S]cysteine. Polyclonal antibodies raised against human p32 cross-reacted with murine p34. These data suggest that p32 and p34 are closely regulated human and murine gene products, respectively, whose synthesis can be modulated by thiol-reactive reagents. Induction of p32 and p34 by these agents, but not by heat shock, suggests that these proteins are a subset of stress-inducible gene products.
 ...
PMID:Induction of 32- and 34-kDa stress proteins by sodium arsenite, heavy metals, and thiol-reactive agents. 309 79

Our previous studies showed that 4-S-cysteinylphenol (4-S-CP) and 4-S-cysteaminylphenol (4-S-CAP) inhibit the growth of malignant melanoma and cause depigmentation of black skin. In this study we examined kinetic constants of CP and CAP as substrates for tyrosinases and their properties as sulphydryl scavengers. 4-S-CP and 4-S-CAP were found to be much better substrates for mushroom tyrosinase than L-tyrosine while their 2-S isomers were not the substrates. 4-S-CP and 4-S-CAP were also good substrates for mammalian tyrosinase. Upon tyrosinase oxidation the two phenols conjugated with cysteine to form the cysteinyl derivatives of the corresponding catechols via o-quinone forms. The tyrosinase oxidation product of 4-S-CP had a poor ability to conjugate with alcohol dehydrogenase, a sulphydryl enzyme, while that of 4-S-CAP had a much higher ability. These results suggest that in melanocytes these phenols are oxidised by tyrosinase to the corresponding o-quinone forms, some of which conjugate with sulphydryl enzymes through cysteine residues, thus exerting cytotoxic effects.
 ...
PMID:Mechanism of selective toxicity of 4-S-cysteinylphenol and 4-S-cysteaminylphenol to melanocytes. 310 34


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>