Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cells of the C3 clone of B-16 melanoma synthesize melanin only at confluence after which they senesce and can no longer be passaged. Addition to the cultures of 10(-8)--10(-7) M 12-O-tetradecanoylphorbol-13-acetate (TPA) shortly after plating delayed by about 2 days the onset of melanogenesis. TPA did not, however, affect the growth of the cells or the time at which they reached confluence. The ability of a series of phorbol esters to delay melanogenesis correlated with their tumor-promoting activity on mouse skin. The optimum time for addition of TPA was within the first 24 hr after plating; the inhibitory effect decreased when TPA was added at later points. alpha-melanocyte-stimulating hormone (5 x 10(-7) M) added to B-16 cultures 24 hr after plating slowed the growth of the cells and caused them to differentiate when still subconfluent. TPA also inhibited this alpha-melanocyte-stimulating hormone-induced melanogenesis. These results suggest that TPA inhibits a very early stage in a stepwise process that leads to the differentiation of these cultures. For reasons that are not apparent, the cells eventually escape from this inhibition. The B-16 melanoma cell culture system may be useful for studying the mechanism by which TPA and related tumor promoters affect cellular differentiation.
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PMID:Effect of phorbol ester tumor promoters on the expression of melanogenesis in B-16 melanoma cells. 47 28

Cloudmann S 91 mouse melanoma cells treated for 5 days with melanocyte-stimulating hormone (MSH), cytochalasin B (CB), or both, exhibited changes in cell volume, population, nucleation, and pigment production. Cells treated with CB or CB in combination with MSH were eight to nine times larger, rounder, multinucleated, and heavily pigmented. CB alone increased melanin and DNA per nucleus threefold. CB in combination with MSH increased melanin per nucleus 30-fold. Data on DNA per nucleus suggest that CB-treated cells remained in the G phase longer than did control cells. MSH alone caused a reduction in cell population and a fourfold increase in melanin per nucleus.
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PMID:Response of Cloudman S91 melanoma cells to melanocytestimulating hormone: enhancement by cytochalasin B. 99 99

A hybrid toxin targeted to melanotropin receptors and selectively cytotoxic to melanoma cell lines in vitro has recently been developed. The toxin, a recombinant fusion protein (designated DAB389-MSH), contains the peptide sequences of alpha-melanocyte-stimulating hormone (alpha-MSH) and the catalytic (cytotoxic; Fragment A) and lipophilic (part of Fragment B) domains of diphtheria toxin. In the present study, binding of DAB389-MSH to melanotropin receptors in biopsy specimens of human and mouse melanoma metastases was assessed by measuring its ability to inhibit binding of a radiolabeled, superpotent analogue of alpha-MSH (125I-[Nle4,D-Phe7]-alpha-MSH; 125I-NDP-MSH) and comparing its potency in this system with those of the established ligands NDP-MSH and alpha-MSH. Radioligand binding to tissue sections in vitro was localized and quantified by autoradiography and image analysis. DAB389-MSH inhibited binding of 125I-NDP-MSH to experimental murine B16-F1C23 melanoma metastasis tissue and to melanoma metastases of three patients. In both mouse and human melanoma tissues, concentration-response relationships for DAB389-MSH-mediated inhibition of 125I-NDP-MSH binding were parallel, and its maximal effects were comparable in magnitude, to those of NDP-MSH and alpha-MSH. Half-maximal peptide concentrations for inhibition of 125I-NDP-MSH binding to mouse melanoma tissue sections were: NDP-MSH, 0.63 nM; alpha-MSH, 3.14 nM; and DAB389-MSH, 10.1 nM. In human melanoma tissues, the respective half-maximal peptide concentrations for inhibition of 125I-NDP-MSH binding to mouse melanoma tissue sections were: NDP-MSH, 1.80 nM; alpha-MSH, 2.43 nM; and DAB389-MSH, 11.9 nM. Taken together, these results suggest that NDP-MSH, alpha-MSH, and DAB389-MSH bind to a common melanotropin receptor in human metastatic melanoma cells. Since previous work has shown that melanotropin receptors are detectable in melanoma metastases of about 80% of human patients, malignant melanoma cells of many patients may be susceptible to killing by the melanotropin receptor-targeted cytotoxin DAB389-MSH.
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PMID:Interaction of an alpha-melanocyte-stimulating hormone-diphtheria toxin fusion protein with melanotropin receptors in human melanoma metastases. 131 97

The effect of alpha-melanocyte-stimulating hormone (alpha-MSH) on protein kinase C activity and distribution was investigated in murine B16 F1 melanoma cells. alpha-MSH was found to induce an increased association of protein kinase C (PKC) activity with the particulate fraction of the cells, with an associated loss of enzyme activity from the soluble fraction. The peak response to alpha-MSH occurred between 20 and 60 min of incubation time, and enzyme activities redistributed to those seen in the control cells over the following 12 to 24 h. The average response to alpha-MSH (1 nmol/l) was an approximate 2.5-fold increase in the percentage of enzyme activity associated with the membrane within 1 h of exposure to alpha-MSH; the particulate enzyme activity represented 19.2 +/- 4.4% of total activity in the absence of alpha-MSH and 50.7 +/- 4.7% (means +/- S.E.M., n = 9, P less than 0.005) in the presence of alpha-MSH (1 nmol/l). Cells which had a relatively small percentage of their PKC activity on the membrane initially were significantly (P less than 0.01) more responsive to alpha-MSH stimulation than cells which initially had a relatively large percentage of PKC activity on the membrane. The association of PKC activity with the membrane showed some evidence of being dose-related to alpha-MSH. This is the first report, to the best of our knowledge, of alpha-MSH activating PKC.
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PMID:Alpha-melanocyte-stimulating hormone stimulates protein kinase C activity in murine B16 melanoma. 131 52

In this study we have compared the effects of different pro-opiomelanocortin (POMC) peptides on melanogenesis and metastasis and their relationship to MSH receptor expression in B16F1 melanoma cells. All peptides, apart from beta-endorphin, increased melanogenesis and the order of potency was Nle4DPhe7-alpha-MSH greater than alpha-MSH greater than ACTH[1-39] greater than des-acetyl alpha-MSH greater than ACTH[1-24]. A similar order of potency was found for metastasis, except for ACTH [1-24], which had a relatively greater effect on metastasis. These findings suggest that the effects on melanogenesis and metastasis are mediated via the same receptor. The results of ligand binding studies also indicated the presence of a single receptor with a KD value for Nle4DPhe7-alpha-MSH of 62 +/- 16pM. This was consistent with crosslinking studies using [125I] Nle4DPhe7-alpha-MSH which produced a single 50-55 kD band on analysis by SDS-PAGE. However, the relative binding affinities of the different peptides, measured by displacement of [125I]-Nle4DPhe7-alpha-MSH, did not closely correlate with the relative potencies in stimulating melanogenesis and metastasis. This suggests that receptor activation and the subsequent biological response is not determined solely by binding affinity.
Melanoma Res 1992 May
PMID:MSH receptor expression and the relationship to melanogenesis and metastatic activity in B16 melanoma. 132 55

The differentiation-inducing activity of doxorubicin on B16 melanoma cells grown in vitro was compared with that of other known differentiation inducers, such as theophylline, retinoic acid, and melanocyte-stimulating hormone (MSH). At drug concentrations resulting in cytostatic effects, doxorubicin and theophylline induced morphological changes (dendritic-like structures with a terminal melanin granule) with an enhancement of total melanin content and tyrosinase activity. Retinoic acid did not alter melanin content and cell morphology, although it affected cell growth. MSH enhanced total melanin content and tyrosinase activity, with no significant morphological changes. Flow cytometric analysis showed that MSH led to an accumulation of cells in G1 phase whereas doxorubicin induced an accumulation of cells in G2 + M. Studies on DNA content in doxorubicin-treated cells, selected on the basis of a morphologically differentiated pattern, showed a clustering of these cells in G2 + M, probably due to a cytokinesis block. Thus doxorubicin can induce cell differentiation comparable with other differentiation inducers.
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PMID:Comparative studies on the effects of doxorubicin and differentiation inducing agents on B16 melanoma cells. 132 7

The alpha-melanocyte-stimulating hormone (alpha-MSH) receptor of B16 mouse melanoma cells was characterized by photoaffinity labelling using radiolabelled photoactive derivatives of alpha-MSH. A doublet band of 43-46 kDa representing a ligand-receptor complex was identified. A novel adaptation of the streptovadin/biotin-based affinity system was used to isolate the alpha-MSH receptor. A probe was synthesized which contained biotin connected to a photolabelled alpha-MSH analogue via a cleavable disulphide linker and which displayed high affinity for the alpha-MSH receptor. Streptavidin-coated magnetic beads were used as a solid support instead of an affinity column. Covalently linked probe-receptor complexes solubilized in Triton X-100 were equilibrated with the beads, and after magnetic separation and washing, specifically bound complexes were treated with dithiothreitol to cleave the disulphide bridge in the biotin-peptide spacer arm and so release the receptor-ligand complex. The identity of the isolated protein was established by SDS/PAGE analysis. Methods to achieve purification to homogeneity and to allow quantitative isolation of the receptor are discussed.
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PMID:Isolation and partial purification of a melanocyte-stimulating hormone receptor from B16 murine melanoma cells. A novel approach using a cleavable biotinylated photoactivated ligand and streptavidin-coated magnetic beads. 132 40

Murine melanoma cells treated with the melanocyte-stimulating hormone (MSH) family of peptides undergo differentiation characterized by enhanced melanogenesis and altered morphology. These effects are mediated via the adenylate cyclase-cAMP pathway leading to activation of protein kinase A (PKA). We have discovered that inhibition of a post-translational modification of chromatin proteins, viz. poly(ADP-ribosylation), also induces melanogenesis and differentiation in these cells. A range of competitive inhibitors (benzamide and its derivatives) of the nuclear enzyme poly(ADP-ribose) polymerase (PADPRP; EC 2.4.2.30) was utilized, and their ability to induce melanogenesis reflected their potency as PADPRP inhibitors. These compounds induced melanogenesis at low doses (20 microM-2 mM) which did not affect cell growth or viability. Induction of melanogenesis was not attributable to inhibition of cyclic nucleotide phosphodiesterase by these compounds. MSH treatment caused a transient rise in cAMP levels (up to 200-fold by 5 min and returning to near basal levels by 5 h). It also stimulated PKA activity up to 5-fold, and the temporal kinetics of this activation mirrored the changes in cAMP levels. In comparison, the PADPRP inhibitors had no effect on either of these processes. These data constitute a novel demonstration of a cAMP-independent mechanism for the induction of melanoma cell differentiation, including melanogenesis.
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PMID:Murine melanoma cell differentiation and melanogenesis induced by poly(ADP-ribose) polymerase inhibitors. 132 52

alpha-MSH was found to decrease the recently characterized dopachrome tautomerase activity in cultures of B16/F10 mouse melanoma cells. Other stimulating agents of melanogenesis, like dibutyryl cyclic AMP, 3-isobutyl-1-methylxanthine, theophylline, retinol, and retinoic acid, caused the same effect. The grade of inhibition depended on the nature of the agent and the time of exposure. In all cases, both melanin production and tyrosinase activity were activated by these treatments, although the grade of tyrosine hydroxylase and dopa oxidase stimulation was different. Moreover, no correlation among the intensities of dopachrome tautomerase inhibition and tyrosinase activation by the tested agents could be obtained. The significance of these results in the regulation of mammalian melanogenesis is discussed.
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PMID:Alpha-MSH and other melanogenic activators mediate opposite effects on tyrosinase and dopachrome tautomerase in B16/F10 mouse melanoma cells. 132 99

Our previous work indicated that IR-alpha-MSH (immunoreactive alpha-melanocyte-stimulating hormone) plasma levels are three times as high in melanoma patients with progressing disease than in disease-free patients, and that the melanoma tumor itself may be the source of IR-alpha-MSH. Further identification of the material in tumor extracts has been carried out in this study, and the results presented here show that the immunoreactivity is associated with a major fraction of about 16 kDa and another of 5-9 kDa. Significant amounts of the immunoreactive material were also found in human melanoma cells but not in culture supernatants. The presence of this material may be related to the melanogenic status of the tumor cells. We have estimated the intracellular IR-alpha-MSH to be within a 0.4 to 2.3 nM range in melanoma tumor cells. We have investigated the melanogenic effect of the IR-alpha-MSH material and its relationship to alpha-MSH. Purified extracts both from metastases and cultured cells were found to promote frog skin darkening as well as tyrosinase activity in Cloudman S91 melanoma cells. The IR material could also displace labeled alpha-MSH from its binding sites in human melanoma cells. Our data clearly indicate that melanoma cells engage in an autocrine production of alpha-MSH-like bioactive peptides by melanoma cells, of larger mol.wt., which are able to bind to MSH receptors. These peptides may be involved in the regulation of melanogenesis and possibly in the growth and proliferation of melanoma cells by an autocrine/paracrine mechanism.
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PMID:Partial characterization of IR-alpha-MSH peptides found in melanoma tumors. 133 93


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