Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1522102 (Melanoma)
 7,698 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

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

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

One skin cancer prevention strategy that we are developing is based on synthesizing and testing melanocortin analogs that reduce and repair DNA damage resulting from exposure to solar ultraviolet (UV) radiation, in addition to stimulating pigmentation. Previously, we reported the effects of tetrapeptide analogs of alpha-melanocortin (alpha-MSH) that were more potent and stable than the physiological alpha-MSH, and mimicked its photoprotective effects against UV-induced DNA damage in human melanocytes. Here, we report on a panel of tripeptide analogs consisting of a modified alpha-MSH core His(6)-d-Phe(7)-Arg(8), which contained different N-capping groups, C-terminal modifications, or arginine mimics. The most potent tripeptides in activating cAMP formation and tyrosinase of human melanocytes were three analogs with C-terminal modifications. The most effective C-terminal tripeptide mimicked alpha-MSH in reducing hydrogen peroxide generation and enhancing nucleotide excision repair following UV irradiation. The effects of these three analogs required functional MC1R, as they were absent in human melanocytes that expressed non-functional receptor. These results demonstrate activation of the MC1R by tripeptide melanocortin analogs. Designing small analogs for topical delivery should prove practical and efficacious for skin cancer prevention.
Pigment Cell Melanoma Res 2009 Oct
PMID:alpha-MSH tripeptide analogs activate the melanocortin 1 receptor and reduce UV-induced DNA damage in human melanocytes. 1971 49

Exposure of cultured human melanocytes to ultraviolet radiation (UV) results in DNA damage. In melanoma, UV-signature mutations resulting from unrepaired photoproducts are rare, suggesting the possible involvement of oxidative DNA damage in melanocyte malignant transformation. Here we present data demonstrating immediate dose-dependent generation of hydrogen peroxide in UV-irradiated melanocytes, which correlated directly with a decrease in catalase activity. Pretreatment of melanocytes with alpha-melanocortin (alpha-MSH) reduced the UV-induced generation of 7,8-dihydro-8-oxyguanine (8-oxodG), a major form of oxidative DNA damage. Pretreatment with alpha-MSH also increased the protein levels of catalase and ferritin. The effect of alpha-MSH on 8-oxodG induction was mediated by activation of the melanocortin 1 receptor (MC1R), as it was absent in melanocytes expressing loss-of-function MC1R, and blocked by concomitant treatment with an analog of agouti signaling protein (ASIP), ASIP-YY. This study provides unequivocal evidence for induction of oxidative DNA damage by UV in human melanocytes and reduction of this damage by alpha-MSH. Our data unravel some mechanisms by which alpha-MSH protects melanocytes from oxidative DNA damage, which partially explain the strong association of loss-of-function MC1R with melanoma.
Pigment Cell Melanoma Res 2009 Dec
PMID:alpha-MSH activates immediate defense responses to UV-induced oxidative stress in human melanocytes. 1965 42