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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Melanoma (melanoma malignum) is a malignant tumor derived from melanin-producing melanocytes. Both environmental factors and genetic predisposition are important in tumor development and progression. If not detected and removed early, it is very aggressive and unresponsive to current therapeutic approaches. Therefore, one of the major goals of melanoma research is to better understand cancer biology, which in turn might result in the development of novel treatment strategies. This article reviews selected aspects of the molecular biology of melanoma with an emphasis on describing the role of transcription factors. These regulatory proteins modulate the expressions of genes, and alterations in transcription factor function are associated with human diseases, including cancer. The transcription factors MITF, NF-kappaB, AP-1, AP-2alpha, Notch, CREB, Ets-1, LEF/TCF/beta-catenin, PAX3, Ski, Snail, and STAT play important roles during the development and progression of melanoma. Both the causes and the consequences of changes in transcription factor expression and/or activity are described based on the most recent literature.
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PMID:[Transcription factors in the development and progression of melanoma]. 1797 61

Melanoma has a wide spectrum of histologic features which mimic epithelial, hematologic, mesenchymal, and neural tumors. Immunohistochemistry has been the primary tool to distinguish melanomas from these other tumors; it has also been studied for use as an adjunct to distinguish benign and malignant melanocytic tumors and to elucidate prognosis. Furthermore, there has been extensive effort to find a suitable marker to differentiate spindle cell and desmoplastic melanoma from other tumors. We have reviewed the literature investigating melanocytic differentiation markers, proliferation markers, immunomodulatory markers, signaling molecules, and nerve growth factors and receptors. Despite the proliferation of immunohistochemical markers, S-100 remains the most sensitive marker for melanocytic lesions, while markers such as HMB-45, MART-1/Melan-A, tyrosinase, and MITF demonstrate relatively good specificity but not as good sensitivity as S-100. No marker has proven useful in distinguishing spindle cell and desmoplastic melanomas from other tumors. Ki67 remains the most useful adjunct in distinguishing benign from malignant melanocytic tumors. None of the markers reviewed has been shown conclusively to have prognostic value for melanocytic neoplasms.
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PMID:Immunohistochemical characteristics of melanoma. 1839 7

Partial and some few cases of complete spontaneous regression have been observed in cutaneous melanoma patients but little is known about the molecular mechanisms involved. The Melanoblastoma-bearing Libechov Minipig (MeLiM) is a suitable animal model to study the phenomenon of spontaneous regression because MeLiM pigs exhibit naturally occurring melanomas which regress completely 6 months after birth. In this study, we used suppression subtractive hybridization (SSH) to identify molecular determinants of melanoma regression within swine melanoma tissues and melanoma cell cultures. Several markers involved in cell-adhesion, -communication, -motility, signal transduction, negative regulation of cell proliferation, transport and immune response were identified that correlated with melanoma regression whereas the main genes involved in melanin synthesis showed a strong downregulation. For the most differentially expressed genes, we validated the results obtained by SSH with qRT-PCR and with immunohistochemistry for some of them (CD9, MITF, RARRES1). Most notable, for the first time in melanoma, we identified the retinoic acid responder 1 gene (RARRES1) as a main actor of the regression process in melanoma. This first gene expression study in swine melanoma regression, may contribute to the finding of new therapeutic targets for human melanoma treatment.
Pigment Cell Melanoma Res 2008 Apr
PMID:Identification of differentially expressed genes in spontaneously regressing melanoma using the MeLiM swine model. 1842 8

There is a great variety of histological patterns of skin melanoma and, in particular, that of its metastatic patterns. Malignant melanocytes are capable of influencing tumor-associated antigen expression. As of now, several varieties of melanoma-associated antigens (MAA) have been identified: MART1/melan A, tyrosinase, MITF, gp100, members of MAGE family, S100, CD63 and CD146. Peptides isolated from such molecules can induce MHC-restricted response of cytotoxic T-lymphocytes. It has been shown that level and nature of specific antigen expression caused by melanocytes correlate with tumor stage and a relationship between survival and MAA expression on tumor cells identified. Morphological features, growth pattern and proliferation rate varied in melanoma cell cultures used in our study. Our experiments involved evaluation of changes in the properties of antigens HLA (class 1 and 2), tumor tissue samples and cells isolated from them, which were capable of stable proliferative activity during passages 5, 10, 15, 20, 25, 30 and 35, and assay for MAA content. Levels of the antigens were significantly lower following long-term culturing melanoma cell melanoma cells in vitro. At initial passages (1-5), antigen profile in most cultures was similar to that in tumor tissue samples. Later on each cell population showed greater antigen expression heterogeneity matched by increased number of cells going through mitotic cycle; their nuclei were stained with antibodies to Ki-67. No HLF A/B/C molecule expression took place during tumor cell culturing: stained cells--in 68.9% of cultures (passages 1-5) and 36.3% (passage 35). However, HLA DQ/DP/DR molecule identification showed an inverse relationship: 44.1% (passage 5) while virtually all the cell lines did synthesize those molecules after passage 35. Hence, MAA and MHC (class 1 and 2) antigens expression in tumor cell should be monitored when they are used for preparation of autologuos and allogenic vaccines. In case of allogenic vaccine production, cell lines capable of stable production of MAA should be selected.
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PMID:[An immunocytochemical investigation of antigen expression by skin melanoma cells cultured for vaccine production]. 1865 34

For the immunohistochemical analysis of melanoma, various serological reagents are available. Melanocyte differentiation markers are reactive with cells and tumors of melanocytic lineage. HMB45 to gp100 has been the most commonly used melanocyte differentiation marker. Recently it was complemented by reagents such as antibodies to Melan-A/MART-1 and tyrosinase. Other reagents, whose reactivity is not strictly confined to melanocyte differentiation antigens, are also commonly used. Among them, the most prominent is S100. Other reagents are D5 to MITF or PNL-2. The properties of these reagents are presented, and their usefulness as markers in the setting of metastatic melanoma in sentinel lymph nodes is discussed.
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PMID:Serological reagents for the immunohistochemical analysis of melanoma metastases in sentinel lymph nodes. 1869 16

Several parallels between stem cell biology and tumour behaviour have been discovered in recent times. Such commonality is apparent in the unlimited capacity for cell division together with the lack of a differentiated phenotype in embryonic and adult stem cells, traits shared with tumour cells. Differentiation is a tightly regulated process that is mediated by the actions of multiple transcription factor families. The POU domain-containing family of transcription factors contains multiple mammalian members divided into six classes, which can be expressed broadly or in a cell-specific manner, and which are regulators of cell fate decisions of many different lineages. Target gene regulation can occur via a POU factor acting alone, or in combination with other POU proteins, ubiquitous co-activators or co-repressors, or other lineage restricted transcription factors. Aberrant levels of POU proteins have been found in several malignancies, including melanoma, connecting the otherwise developmentally restricted gene regulatory functions of POU transcription factors to the critical determinants of malignant transformation. Here, we focus on the role of the BRN2 (POU3F2/N-Oct-3) transcription factor in the melanocytic lineage where it may co-ordinate normal developmental cues that can be re-activated in melanoma. Recent studies have shown BRN2 to be responsive to MAPK pathway activation and to modulate the levels of MITF so as to suppress the differentiated melanocytic phenotype and to enhance tumour metastasis.
Pigment Cell Melanoma Res 2008 Dec
PMID:POU domain transcription factors: BRN2 as a regulator of melanocytic growth and tumourigenesis. 1898 36

Expression profile analysis clusters Gpnmb with known pigment genes, Tyrp1, Dct, and Si. During development, Gpnmb is expressed in a pattern similar to Mitf, Dct and Si with expression vastly reduced in Mitf mutant animals. Unlike Dct and Si, Gpnmb remains expressed in a discrete population of caudal melanoblasts in Sox10-deficient embryos. To understand the transcriptional regulation of Gpnmb we performed a whole genome annotation of 2,460,048 consensus MITF binding sites, and cross-referenced this with evolutionarily conserved genomic sequences at the GPNMB locus. One conserved element, GPNMB-MCS3, contained two MITF consensus sites, significantly increased luciferase activity in melanocytes and was sufficient to drive expression in melanoblasts in vivo. Deletion of the 5'-most MITF consensus site dramatically reduced enhancer activity indicating a significant role for this site in Gpnmb transcriptional regulation. Future analysis of the Gpnmb locus will provide insight into the transcriptional regulation of melanocytes, and Gpnmb expression can be used as a marker for analyzing melanocyte development and disease progression.
Pigment Cell Melanoma Res 2009 Feb
PMID:Gpnmb is a melanoblast-expressed, MITF-dependent gene. 1898 39

Although microRNAs (miRNAs) are key regulators of gene expression in normal human physiology and disease, transcriptional regulation of miRNAs is poorly understood, because most miRNA promoters have not yet been characterized. We identified the proximal promoters of 175 human miRNAs by combining nucleosome mapping with chromatin signatures for promoters. We observe that one-third of intronic miRNAs have transcription initiation regions independent from their host promoters and present a list of RNA polymerase II- and III-occupied miRNAs. Nucleosome mapping and linker sequence analyses in miRNA promoters permitted accurate prediction of transcription factors regulating miRNA expression, thus identifying nine miRNAs regulated by the MITF transcription factor/oncoprotein in melanoma cells. Furthermore, DNA sequences encoding mature miRNAs were found to be preferentially occupied by positioned-nucleosomes, and the 3' end sites of known genes exhibited nucleosome depletion. The high-throughput identification of miRNA promoter and enhancer regulatory elements sheds light on evolution of miRNA transcription and permits rapid identification of transcriptional networks of miRNAs.
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PMID:Chromatin structure analyses identify miRNA promoters. 1905 95

There are currently no effective therapies for metastatic melanoma and targeted immunotherapy results in the remission of only a very small percentage of tumors. In this study, we show that the noncanonical Wnt ligand, Wnt5A, can increase melanoma metastasis in vivo while down-regulating the expression of tumor-associated antigens important in eliciting CTL responses (e.g., MART-1, GP100, and tyrosinase). Melanosomal antigen expression is governed by MITF, PAX3, and SOX10 and is inhibited upon signal transducers and activators of transcription 3 (STAT3) activation, via decreases in PAX3 and subsequently MITF expression. Increasing Wnt5A in Wnt5A-low cells activated STAT3, and STAT3 was decreased upon Wnt5A knockdown. Downstream targets such as PAX3, MITF, and MART-1 were also affected by Wnt5A treatment or knockdown. Staining of a melanoma tissue array also highlighted the inverse relationship between MART-1 and Wnt5A expression. PKC activation by phorbol ester mimicked Wnt5A effects, and Wnt5A treatment in the presence of STAT3 or PKC inhibitors did not lower MART-1 levels. CTL activation studies showed that increases in Wnt5A correspond to decreased CTL activation and vice versa, suggesting that targeting Wnt5A before immunotherapy may lead to the enhancement of current targeted immunotherapy for patients with metastatic melanoma.
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PMID:Wnt5A regulates expression of tumor-associated antigens in melanoma via changes in signal transducers and activators of transcription 3 phosphorylation. 1907 88

Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which play a crucial protective role against skin photocarcinogenesis. The present study was designed to determine the effects of 6-benzylaminopurine (6-BAP) on melanogenesis and elucidate the molecular events of melanogenesis induced by 6-BAP. To elucidate the pigmenting effect of 6-BAP and its mechanism, several experiments were performed in B16 melanoma cells. Melanin content, tyrosinase activity, cAMP production, and Western blots for proteins which are involved in melanogenesis were introduced in this study. Melanin content and tyrosinase activity increased in response to treatment with 6-BAP in a concentration-dependent manner. The tyrosinase, TRP-1, TRP-2 and MITF protein levels were found to increase significantly in response to 6-BAP in a time-dependent manner. In addition, Western blot analysis revealed that 6-BAP increased the phosphorylated level of CRE-binding protein. The increased melanin synthesis that was induced by treatment with 6-BAP treatment was reduced significantly in response to co-treatment with H-89 [a protein kinase A (PKA) inhibitor], whereas co-treatment with SB203580 (a p38 MAPK inhibitor) and Ro-32-0432 (a PKC inhibitor) did not attenuate the increase in melanin content levels that was induced by 6-BAP. In a cAMP production assay, 6-BAP did not increase the intracellular cAMP level. These findings suggest that 6-BAP activates PKA via a cAMP-independent pathway and subsequently stimulates melanogenesis by up-regulating MITF and tyrosinase expression.
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PMID:6-Benzylaminopurine stimulates melanogenesis via cAMP-independent activation of protein kinase A. 1912 6


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