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)

alpha-Melanocyte stimulating hormone (alpha-MSH) was found significantly to reduce tumour necrosis factor-alpha (TNF-alpha) stimulated upregulation of intercellular adhesion molecule-1 (ICAM-1) in normal adult cutaneous melanocytes. The maximum inhibitory response to alpha-MSH was obtained at around 10(-10) mol/L alpha-MSH when cells were coincubated with alpha-MSH and TNF-alpha for 24 h. alpha-MSH had little or no effect on basal ICAM-1 expression in melanocytes and the effects of alpha-MSH could be mimicked with 3-isobutyl-1-methylxanthine (IBMX). Preliminary data in three human melanoma cell lines also showed alpha-MSH and forskolin to be effective in significantly reducing TNF-alpha stimulated ICAM-1 expression over 24 h. The extent of the inhibition varied from cell line to cell line and was greatest in those cells with the highest number of alpha-MSH receptors. These data suggest that alpha-MSH has the ability to oppose the action of the pro-inflammatory cytokine TNF-alpha on melanocytes and melanoma cells.
 ...
PMID:alpha-Melanocyte stimulating hormone inhibits tumour necrosis factor-alpha stimulated intercellular adhesion molecule-1 expression in normal cutaneous human melanocytes and in melanoma cell lines. 958 Aug 17

We have previously reported high immunoreactive alpha-MSH (IR-alpha-MSH) concentrations in melanoma patients' plasma, as well as significant amounts in melanoma metastases and cells grown in culture. Necrosis within the melanoma tumour leads to a massive proteolysis of intracellular proteins and release of cell content: this might significantly contribute to the elevated IR-alpha-MSH plasma levels measured in melanoma patients. To test this hypothesis, we studied the necrosis-related release of MSH from human melanoma cells, using a specific radioimmunoassay. The studies of fine-needle biopsies indicated that most of the human melanoma tumour exudates tested contained very high MSH concentrations (> 500 pg/ml; 14/15), while plasma levels were generally normal (< or = 25 pg/ml; 10/15). The level in an exudate from a non-melanoma tumour type was < 40 pg/ml. In vitro studies showed that release of the IR-alpha-MSH was time- and temperature-dependent, and related to cell death.
 ...
PMID:alpha-Melanotropin immunoreactivity in human melanoma exudate is related to necrosis. 964 Feb 35

Reiterated selection in vivo of B16 murine melanoma cells for enhanced liver metastatic ability yielded a cel line (B16-LS9) dramatically overexpressing a constitutively active hepatocyte growth factor/scatter factor (HGF/SF) receptor, the product of the c-met proto-oncogene. Most likely because of their overexpressing c-met, B16-LS9 cells appear to be more responsive than parental B16-F1 cells to HGF stimulation, in terms of motility, invasion, and growth. They are also more pigmented, and express higher levels of tyrosinase as compared to parental B1 6-F1 cells. Therefore, we set out to explore whether HGF/SF and the liver might influence the differentiation state of B1 6 cells. We found that HGF/SF and MSH, two factors which reportedly have a strong influence on the phenotype and the malignant behavior of melanoma cells, may act at different levels, and with opposite results, on the regulation of gene expression. In fact, while MSH induces, at the transcriptional level, an increase in the production of both c-met and tyrosinase, HGF/SF, in contrast, promotes a decrease in the expression of both c-met and tyrosinase, however at a posttranscriptional level. These two opposite effects can counter-balance each other, when the cells are treated with both factors at the same time, apparently through a mechanism involving MAP kinase activation. The effects were, however, additive when morphological changes were considered. Most intriguingly, we also describe a very strong downregulatory activity, limited to tyrosinase expression, by hepatocytes in coculture with B16 cells. This activity, also at the posttranscriptional level, is much stronger than that exerted by HGF/SF, and appears to be due to a labile soluble factor produced by the hepatocytes.
 ...
PMID:Hepatocyte growth factor/scatter factor and hepatocytes are potent downregulators of tyrosinase expression in B16 melanoma cells. 977 24

alpha-Melanocyte stimulating hormone (alpha-MSH) analogs, cyclized through site-specific rhenium (Re) and technetium (Tc) metal coordination, were structurally characterized and analyzed for their abilities to bind alpha-MSH receptors present on melanoma cells and in tumor-bearing mice. Results from receptor-binding assays conducted with B16 F1 murine melanoma cells indicated that receptor-binding affinity was reduced to approximately 1% of its original levels after Re incorporation into the cyclic Cys4,10, D-Phe7-alpha-MSH4-13 analog. Structural analysis of the Re-peptide complex showed that the disulfide bond of the original peptide was replaced by thiolate-metal-thiolate cyclization. A comparison of the metal-bound and metal-free structures indicated that metal complexation dramatically altered the structure of the receptor-binding core sequence. Redesign of the metal binding site resulted in a second-generation Re-peptide complex (ReCCMSH) that displayed a receptor-binding affinity of 2.9 nM, 25-fold higher than the initial Re-alpha-MSH analog. Characterization of the second-generation Re-peptide complex indicated that the peptide was still cyclized through Re coordination, but the structure of the receptor-binding sequence was no longer constrained. The corresponding 99mTc- and 188ReCCMSH complexes were synthesized and shown to be stable in phosphate-buffered saline and to challenges from diethylenetriaminepentaacetic acid (DTPA) and free cysteine. In vivo, the 99mTcCCMSH complex exhibited significant tumor uptake and retention and was effective in imaging melanoma in a murine-tumor model system. Cyclization of alpha-MSH analogs via 99mTc and 188Re yields chemically stable and biologically active molecules with potential melanoma-imaging and therapeutic properties.
 ...
PMID:Design and characterization of alpha-melanotropin peptide analogs cyclized through rhenium and technetium metal coordination. 978 97

We recently reported that a majority of hybrids generated in vitro between weakly metastatic mouse Cloudman S91 melanoma cells and human or mouse macrophages showed enhanced metastatic potential. With few exceptions, hybrids with enhanced metastatic potential also had elevated basal melanin content and increased responsiveness to MSH compared to parental cells. Here we investigated the hybrid melanotic phenotype in more detail, comparing the pigmentary systems of hybrids and parental Cloudman S91 cells by several techniques. Cells were studied by electron microscopy, cell lysates were analyzed for tyrosinase (E.C.1.14.18.1) activity, and melanosomal proteins were analyzed by gel electrophoresis and immunoblotting. Melanosomes in parental Cloudman melanoma cells were few in number and relatively amorphous, whereas those in the hybrids were numerous and heavily pigmented, containing highly organized lattice structures. Both basal and MSH-inducible tyrosinase activities were elevated several fold in hybrids compared to parental cells. Tyrosinase, TRP-2, and LAMP-1 from hybrids migrated more slowly on gels compared to the same proteins from parental melanoma cells, consistent with increased glycosylation. Migration of LAMP-1 from hybrids was similar to that from peritoneal macrophages, which also appeared to be more heavily glycosylated than LAMP-1 from Cloudman cells. By using 3H-glucosamine as a marker of N-glycosylation, its incorporation into tyrosinase and LAMP-1 was found to be elevated in hybrids, suppressed by N-glycosylation inhibitors, and stimulated by MSH to a greater degree in hybrids compared to parental cells. These results indicate N-glycosylation as an important regulatory pathway for MSH-induced melanogenesis and further suggest that altered N-linked glycosylation may be an underlying mechanism for regulation of both melanogenesis and metastasis in macrophage x melanoma hybrids.
 ...
PMID:Melanoma x macrophage fusion hybrids acquire increased melanogenesis and metastatic potential: altered N-glycosylation as an underlying mechanism. 987 1

We have previously reported that neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) successfully inhibited Matrigel invasion and haptotactic migration of B16-BL6 melanoma cells towards both fibronectin and laminin without affecting their growth. In the present study, we investigated the inhibitory mechanism of tumor cell motility by alpha-MSH. Alpha-MSH significantly blocked the autocrine motility factor (AMF)-enhanced cell motility. However, alpha-MSH did neither prevent the secretion of AMF from B16-BL6 cells nor alter the expression level of AMF receptor (gp78). On the other hand, alpha-MSH induced the secretion of the motility inhibitory factor(s) from B16-BL6 cells in a concentration- and time-dependent manner. The induction of the motility inhibitor(s) was proportional to increasing levels of intracellular cAMP induced by alpha-MSH as well as forskolin, and the activity was abolished by an adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA). The motility-inhibiting activity in conditioned medium (CM) from alpha-MSH-treated B16-BL6 cells was found to have a m.w. below 3 kDa after fractionation. This activity was abolished by boiling but insensitive to trypsin. The treatment of tumor cells with cycloheximide reduced the activity in alpha-MSH-stimulated CM. Our results suggest that alpha-MSH inhibited the motility of B16-BL6 cells through induction of autocrine factor(s).
 ...
PMID:Induction of autocrine factor inhibiting cell motility from murine B16-BL6 melanoma cells by alpha-melanocyte stimulating hormone. 1007 23

153N-6 (H-[Met5,Pro6,D-Phe7,D-Trp9,Phe10]-MSH(5-13)) has emerged as the most potent antagonist of alpha-MSH activity on Xenopus laevis melanophores, from a library of 32 360 peptides based on alpha-MSH(5-13) [22]. A recent report has confirmed our observation that 153N-6 also binds to mammalian melanocortin receptors. Here we report the receptor-binding affinities and biologic activities of 153N-6 and 17 selected alpha-MSH analogues at the native MCI receptor expressed by murine B16 melanoma cells. Our intention is to determine the structural requirements for agonism and competitive antagonism of melanocortin activity at the MC1-R and to discover more potent antagonists. 153N-6 was able to inhibit the action of native alpha-MSH and the potent synthetic agonist, [Nle4,D-Phe7]alpha-MSH, at the murine MC1-R. However, the Ki of 153N-6 was 439 times higher than that of alpha-MSH and 4475 times higher than that of [Nle4,D-Phe7]alpha-MSH; too high to allow 153N-6 to be considered as a practical antagonist for use in vivo (Ki of 153N-6 = 9.0 X 10(-6) M). Because Met4 is an important component of alpha-MSH binding at the MC1-R, we investigated alpha-MSH(1-13) and alpha-MSH(4-13) analogues to produce compounds with higher MC1-R-binding affinity than 153N-6. The binding affinity of 153N-6 was not significantly different from alpha-MSH(5-13), but it was 232 times lower than alpha-MSH(4-13). Coupling of H-Nle (as an isosteric replacement for Met) or acetyl-Nle to the N-terminus of 153N-6 raised the binding affinity by a factor of 46, but this and all full-length alpha-MSH analogues with Met or Nle in position 4 were full agonists of the MC1-R. A full-length alpha-MSH(1-13) derivative of 153N-6 with Ala4 did not exhibit significantly greater binding affinity than 153N-6 and appeared to be a partial agonist at the MC1-R in the cAMP assay. These data suggest that Met4 is an important determinant of the intrinsic efficacy of melanocortins as well as their binding affinity at the MCI-R. Pro6 and Phe10 (with respect to alpha-MSH) were found to be the most influential substitutions that determined the antagonist activity of 153N-6.
 ...
PMID:Synthesis of 153N-6 analogues and structure-function analysis at murine melanocortin-1 (MC1) receptors. 1044 99

We tested the endogenous tripeptide TRH (thyrotropin releasing hormone) ability to bind to MC (melanocortin) receptor subtypes. We discovered that TRH binds to the human MCI receptor expressed in COS cells and to murine B16 melanoma cells with 5790+/-1010 nM and 6370+/-1260 nM Ki's, respectively. TRH did not bind to the human MC3, MC4 or MC5 receptor subtypes. Moreover, TRH also stimulated cAMP production in murine B16 melanoma cells reaching the same maximum level of cAMP as found for alpha-MSH. However, several analogues of TRH, including TRH-OH, TRH-Gly-NH2 and other analogues, where each of the three amino acid residues in TRH had been exchanged by a related residue, did not bind to any of the MC receptors tested in this study. C(alpha) atoms of molecular models of TRH and the core of a MSH peptide were aligned with r.m.s. of 0.01 A. Moreover, TRH could be docked into a binding pocket of a molecular model of the MC1 receptor at only a little higher energy than a short cyclic MSH peptide. The data indicate a similarity in the mode of TRH and MSH activation of the MCI receptor.
 ...
PMID:Thyrotropin releasing hormone (TRH) selectively binds and activates the melanocortin 1 receptor. 1044

Radiolabeled alpha-melanocyte stimulating hormone (alpha-MSH) analogs were examined in melanoma-bearing mice to determine the effects of peptide length, structure, and radiometal chelation chemistry on tumor targeting and in vivo biodistribution. The linear alpha-MSH analogs [Nle4,D-Phe7]alpha-MSH (NDPMSH) and [D-Phe7]alpha-MSH(5-10) (DPMSH) were radiolabeled with 99mTc and 188Re via the addition of tetrafluorophenyl mercapto-acetylglycylglycyl-gamma-aminobutyrate (MAG2) or tetrapeptide Ac-Cys-Gly-Cys-Gly (CGCG) chelation moieties. 125I-Tyr2-NDPMSH was obtained by direct iodination of the Tyr2 residue. Tumor uptake of 99mTc-labeled CGCG- and MAG2-NDPMSH analogs at 30 min postinjection were 6.52 +/- 1.11 %ID/g and 4.17 +/- 1.34 %ID/g, respectively, resulting in a significantly higher tumor-to-blood uptake ratio than that of 125I-NDPMSH or a shorter alpha-MSH analog, 99mTc-CGCG-DPMSH. The combination of radiolabeling efficacy and in vivo tumor uptake highlights the potential of 99mTc-CGCG-NDPMSH as a melanoma imaging agent.
 ...
PMID:In vivo evaluation of 99mTc/188Re-labeled linear alpha-melanocyte stimulating hormone analogs for specific melanoma targeting. 1058 8

It was recently reported that a majority of hybrids generated in vitro between weakly metastatic mouse Cloudman S91 melanoma cells and human or mouse macrophages showed enhanced metastatic potential (Rachkovsky et al., 1998). With few exceptions, hybrids with enhanced metastatic potential also had elevated basal melanin content, enhanced chemotactic responses to fibroblast-conditioned media, and stronger responsiveness to MSH compared to parental cells. Analyses revealed that altered N-glycosylation in metastatic hybrids could explain the multiple phenotypic changes. Tyrosinase, TRP-2 and LAMP-1 from hybrids migrated more slowly on gels compared to the same proteins from parental melanoma cells, consistent with increased glycosylation. Migration of LAMP-1 from hybrids was similar to that from peritoneal macrophages which also appeared to be more heavily glycosylated than LAMP-1 from Cloudman cells. The incorporation of 3H-glucosamine, as a marker of N-glycosylation, into tyrosinase and LAMP-1 was found to be elevated in hybrids, suppressed by N-glycosylation inhibitors and stimulated by MSH to a greater degree in hybrids compared to parental cells. These results indicate N-glycosylation as an important regulatory pathway for MSH-induced melanogenesis, and further suggest that altered N-linked glycosylation may be an underlying mechanism for regulation of both melanogenesis and metastasis in macrophage x melanoma hybrids.
 ...
PMID:Altered N-glycosylation in macrophage x melanoma fusion hybrids. 1064 5


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