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)

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

A conjugate made of alpha-MSH as a drug carrier and melphalan has been designed in order to target human melanoma cells. Iodination of the alpha-MSH moiety led to a relatively stable tracer which could be easily separated and analysed by reverse phase high pressure liquid chromatography. The conjugate was found to be unstable at neutral pH and a serious denaturation can take place at concentrations exceeding 100 micrograms/ml, especially in plasma. Receptor-mediated cytotoxicity has been shown by the use of cultured alpha-MSH receptor positive/negative cells as well as in vivo B16 murine melanoma model. Body distribution and uptake of the labelled compound were unaltered as compared to those of labelled free hormone. alpha-MSH receptor recognition properties also remained unchanged with a better apparent affinity of the conjugate probably due to the alkylating activity of melphalan itself. Using human melanoma dendritic cells expressing more than 10,000 alpha-MSH binding sites per cell as an in vitro model, we were able to demonstrate higher cytotoxicities as compared to melphalan-treated cells. In contrast, melanoma cells with low receptivity did not show higher cytotoxicity. P388D1 mouse plasmocytoma cells lacking receptors were much more sensitive to melphalan than the conjugate. This phenomenon appeared to be related with the number of binding sites expressed at the time of the experiment as well as cell differentiation and the doubling time. Our findings strongly support the concept of a receptor-mediated cytotoxicity and may enable the in vivo melphalan delivery to target tissues to be increased, achieving an improvement of drug penetration inside melanoma cells.
Melanoma Res
PMID:Human melanoma targeting with alpha-MSH-melphalan conjugate. 166 32

Normal human cells, cells from nonmalignant proliferative lesions, and primary and metastatic tumor cells can be maintained in vitro and analyzed for requirements for growth in chemically defined media. The human melanocytic cell system with normal melanocytes, precursor nevus cells, and primary and metastatic melanoma cells has been extensively studied for the phenotypic properties of the cells, including their requirements for exogenous growth factors and other mitogens. In high calcium-containing W489 medium, normal melanocytes require four supplements: IGF-I (or insulin); bFGF, TPA, and alpha-MSH. Nevus cells are largely independent of bFGF. Depletion of TPA from medium is not as detrimental to nevus cells as it is to melanocytes, but the phorbol ester is still essential for maintenance of the typical nevic phenotype. Primary melanoma cells require at least one growth factor, IGF-I (or insulin), for continuous proliferation. On the other hand, metastatic cells of melanoma as well as of carcinomas of colon and rectum, bladder, ovary, and cervix are able to proliferate after a short adaptation period in medium depleted of any growth factors and other proteins. Doubling times of metastatic tumor cells in protein-free medium are only 30-60% longer than in FCS-containing medium. The growth autonomy of human tumor cells is apparently due to the endogenous production of growth factors. Likely candidates for autocrine growth stimulation of human tumor cells are TGF-alpha, TGF-beta, and PDGF. Melanoma and colorectal carcinoma cells express functional EGF/TGF-alpha receptors, and produce TGF-alpha, indicating that this growth factor is produced for autocrine stimulation. In addition to the use of anti-growth factor antibodies, other strategies for the inhibition of autocrine growth stimulation include mAbs to growth factor receptors, soluble receptors, receptor-mimicking antiidiotype antibodies, and active immunization against growth factors. Whether any of these therapeutic approaches is clinically feasible will need to be determined in extensive preclinical investigations.
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PMID:Growth-regulatory factors for normal, premalignant, and malignant human cells in vitro. 240 78

Transfection of class I H-2Kb or H-2Kd into cells of a pigmented subclone of B16-F10 BL6 (termed BL6-8) results in the loss of melanin production. In contrast, transfected BL6-8 cells expressing H-2Dd, H-2Ld, class I H-21Ak and/or the neor genes maintained their pigmented phenotype. Melanogenesis was also inhibited in cells which expressed the endogenous H-2Kb, but not the endogenous H-2Db, gene. In order to identify the specific defects in the melanogenic pathway responsible for the absence of melanin production, factors known to be related to the regulation of pigment formation were evaluated in H-2K-expressing cells. These studies showed that: (1) transfection of BL6-8 cells with the H-2Kb or H-2Kd, but not with the H-2Dd, H-2Ld or H-21Ak, genes was associated with complete inhibition of tyrosinase activity; (2) alpha-melanocyte-stimulating hormone (MSH) and theophylline (an inhibitor of cAMP phosphodiesterase) failed to stimulate tyrosinase activity in H-2K-positive cells, whereas tyrosinase activities in untransfected, or H-2DdH-2Ld, neor or H-21Ak-transfected cells were dramatically increased by those agents; (3) treatment with MSH had no effect on cAMP levels in H-2K-positive cells but stimulated cAMP levels more than 100-fold in H-2K-negative cells; (4) in contrast to MSH, forskolin, a stimulator of adenylate cyclase, was able to stimulate cAMP levels in all cell lines tested, but in H-2Kb-positive cells the levels of forskolin-induced cAMP were significantly less than those elicited in H-2Kb-negative cells; (5) electron microscopy showed that H-2K-positive cells lacked mature melanosomes; (6) Northern blot analyses showed that H-2K-positive cells lacked mRNA for tyrosinase or for the MSH receptor. Taken together, expression of the endogenous or transfected H-2K gene in BL6 melanoma cells results in down-regulation of the entire melanogenic pathway, including the inhibition of tyrosinase and MSH receptor gene expression, cAMP responses and melanosomal biogenesis.
Melanoma Res 1995 Feb
PMID:Impairment of the melanogenic pathway in B16 melanoma cells transfected with class I H-2 genes. 773 52

The possible mechanisms for the reduced melanin content and poor melanogenic response to MSH was investigated in B16-F10DD differentiation deficient melanoma cells. In particular, the MSH receptor status and associated signal transduction pathway linking to tyrosinase activity in these cells was studied for evidence of any defects. F10DD cells contained high-affinity binding sites for alpha-MSH, with KD values similar to those previously reported for other variants of the B16 melanoma. SDS-PAGE analysis after radioactive ligand cross-linking showed no evidence of gross structural alterations of the receptor. The F10DD cells expressed approximately twice as many receptors as the F10 parent cell line, suggesting a possible feedback response attempting to compensate for the amelanotic condition. The functional integrity of the MSH receptors in F10DD cells was confirmed by the presence of increased levels of cAMP in response to MSH stimulation. These results, coupled with the observation that F10 and F10DD cells express similar levels of tyrosinase mRNA and protein, point to a structural defect in tyrosinase or in the post-translational control mechanisms by which the activity of this enzyme is regulated.
Melanoma Res 1993 Apr
PMID:MSH receptors and function in amelanotic B16 melanoma cells. 839 Aug 76

The fate of alpha-melanocyte-stimulating hormone (alpha-MSH) subsequent to binding to the melanoma melanocortin MC1 receptor is of interest with regard to its potential use in targeting cytotoxic drugs or imaging to melanoma. Tools such as iodinated, photoaffinity-labelled, biotinylated and fluorescent melanocortins are required to study the fate of the ligand during its interaction with the receptor. In this study, a series of probes for the receptor based on the potent analogue, [Nle4,Dphe7]alpha-MSH, have been developed and tested for their potential usefulness. All probes contain the core melanocortin motif His-Phe-Arg-Trp. They bind the receptor readily and appear to have similar intrinsic efficacies to the endogenous peptide, so that biological activity is regulated by their receptor binding affinity. Functional photoaffinity-labelled, biotinylated and fluorescent probes are described. The biotinylated probe binds the receptor when coupled to streptavidin, although with reduced affinity.
Melanoma Res 1996 Apr
PMID:Melanocortin probes for the melanoma MC1 receptor: synthesis, receptor binding and biological activity. 879 Dec 65

Melanoma cells express receptors for melanocyte-stimulating hormone (MSH) in variable abundance. CGP 41251, a derivative of staurosporine with an increased selectivity for protein kinase C (PKC) inhibition, was found to modulate MSH receptors in human D10 and HBL cells and in the mouse B16 cell line. Up-regulation was observed in D10 and B16 cells at a concentration of 290 nM and 190 nM, respectively. In HBL cells, however, the PKC inhibitor induced a pronounced MSH receptor down-regulation with an EC50 of only 32 nM. In D10 and HBL cells, alpha-MSH and CGP 41251 synergistically regulated MSH receptors whereas these agents had an antagonistic effect in B16 cells. PKC stimulation by short-term treatment with phorbol ester had an opposite effect on MSH receptors as compared to CGP 41251. In B16 cells, CGP 41251 at a concentration of 100 nM increased the sensitivity to MSH-induced melanogenesis. The staurosporine derivative inhibited proliferation of HBL, B16, and D10 cells at EC50s of 180 nM, 190 nM, and 520 nM, respectively. Furthermore, CGP 41251 increased the dendricity of the cells. In a concentration range between 300 nM and 1 mu M, CGP 41251 induced a sharp increase of the mean cell diameter from 16 mu m to 19 mu m. Thus, the effects of the selective PKC inhibitor on MSH receptors are induced at lower concentrations than needed for the inhibition of proliferation or for the change in cell morphology. These results suggest that the number of MSH receptors expressed on the surface of cultured melanoma cells correlates with the level of constitutive PKC activity in individual cell lines.
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PMID:A selective protein kinase C inhibitor (CGP 41251) positively and negatively modulates melanoma cell MSH receptors. 890 45

The retinoblastoma protein (pRB), the product of the retinoblastoma gene, is a key regulator of the cell cycle, affecting apoptosis, proliferation and differentiation. Dysregulation of pRB is implicated in the pathogenesis of many cancers, including malignant melanoma. Recently we demonstrated that alpha-melanocyte-stimulating hormone (alpha-MSH)-induced activation of p38 mitogen-activated protein (MAP) kinase leads to differentiation of B16 murine melanoma cells. The current study assesses the ability of alpha-MSH to activate p38 MAP kinase in COLO 853 human melanoma cells and determines whether this is linked to modulation of pRB activity. Treatment of COLO 853 cells with alpha-MSH induced time- and concentration-dependent increases in the phosphorylation of p38 MAP kinase, which corresponded with its ability to induce melanogenesis and inhibit cell growth. SB 203580, a selective inhibitor of p38 MAP kinase, blocked both the alpha-MSH-induced melanogenic response and inhibition of cell growth. Cell cycle analysis using flow cytometry revealed that treatment of COLO 853 cells with alpha-MSH for 72 h led to an increase in the proportion of cells in the G(1) phase and a marked reduction in the amount of phosphorylated pRB. Both of these effects were reversed by pre-treatment of cells with SB 203580. In summary, we have demonstrated for the first time that the alpha-MSH-induced differentiation of COLO 853 human melanoma cells proceeds via a p38 MAP kinase-mediated pathway and is associated with decreased pRB phosphorylation and accumulation of cells in the G(1) phase.
Melanoma Res 2002 Jun
PMID:Differentiation of human melanoma cells through p38 MAP kinase is associated with decreased retinoblastoma protein phosphorylation and cell cycle arrest. 1214 Mar 74

Melanoma is a malignant skin cancer that displays a high rate of tumor cell migration and metastasis. This study examined how corticotropin-releasing hormone (CRH) affects the migration of melanoma cells in order to further understand the relationship between stress and tumor cell migration. The migration assay data showed that CRH treatment increased the level of B16F10 cell migration in a dose- and time-dependent manner. To determine whether the extracellular signal-regulated protein kinase 1/2 (ERK1/2) signaling pathway is involved in the upregulation of melanoma migration, cells were pretreated with an inhibitor of ERK1/2 (PD098059). The pretreatment of PD098059 blocked the increase in cell migration. Furthermore, CRH induced the phosphorylation of ERK1/2. The maximum activation of ERK1/2 by CRH was observed at 15 min. Taken together, these results suggest that CRH is an important mediator that regulates the migration of melanoma cells in the skin during stress through the ERK1/2 signaling pathway.
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PMID:Enhancement of cell migration by corticotropin-releasing hormone through ERK1/2 pathway in murine melanoma cell line, B16F10. 1718 33

Melanoma primary tumors can be, in most cases, removed surgically, whereas there is no satisfactory treatment for metastatic melanoma, being almost always lethal at this stage. Therefore, early detection of primary melanoma tumors is essential. The finding that melanocortin-1 receptor (MC1R) is overexpressed in isolated melanoma cells and melanoma tissues led to the radiolabeling of several alpha-melanocyte-stimulating hormone (alpha-MSH) analogs for early detection and treatment of melanoma. We have coupled the alpha-MSH analog Ac-Nle-Asp-His-d-Phe-Arg-Trp-Gly-Lys-NH(2), through the epsilon-amino group of Lys(11), to a pyrazolyl-containing chelator (pz). The resulting pz-alpha-MSH analog reacted with the fac-[(99m)Tc(CO)(3)](+) moiety, giving [Ac-Nle(4),Asp(5),d-Phe(7),Lys(11)(pz-(99m)Tc(CO)(3))]alpha-MSH(4-11) in high yield, high specific activity and high radiochemical purity. This radioconjugate, which presents remarkable stability in vitro, exhibited time- and temperature-dependent internalization (4 h at 37 degrees C; 56.7% maximum internalization) and high cellular retention (only 38% was released from the cell after 5 h) in murine melanoma B16F1 cells. A significant tumor uptake [4.2+/-0.9%ID/g, at 4 h postinjection (p.i.)] was also obtained in melanoma-bearing C57BL6 mice. The in vivo affinity and specificity of the radioconjugate to MC1R were demonstrated by receptor-blocking studies with the potent NDP-MSH agonist (63.5% reduction in tumor uptake at 4 h p.i.).
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PMID:A (99m)Tc(CO)(3)-labeled pyrazolyl-alpha-melanocyte-stimulating hormone analog conjugate for melanoma targeting. 1815 48


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