Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of HLA class I molecules is essential for the recognition of tumor cells by CD8+ T cells. In this study, 48 bioptic samples of 42 patients in all stages of melanoma were investigated after short-time cultivation of tumor cells. To confirm melanocytic origin of cultured cells, samples were screened for mRNA expression of melanoma markers gp100, tyrosinase, MAGE-3, MelanA, and MUC18 by reverse transcriptase-polymerase chain reaction. Surface expression of specific HLA-A and -B allospecificities on melanoma cells were analyzed with a standard microcytotoxicity assay after stimulation with interferon (IFN)-alpha and compared with the background found in peripheral blood mononuclear cells from the corresponding patients. Immunohistochemistry and flow cytometry confirmed specific losses in cases where the appropriate monoclonal antibodies were available. The level of expression of HLA-I, HLA-II, and intercellular adhesion molecule 1 antigens on melanoma cells cultured in the presence or absence of IFN-alpha and IFN-gamma was determined cytofluorometrically. All cell cultures tested were found to be positive for one or more melanocytic markers by reverse transcriptase-polymerase chain reaction. The specific HLA-I alleles on the cultured cells were detectable in 45 of 48 samples. In 11 cases a specific loss of one HLA-I allele was observed (2 x A2, B7, B8, B18, 4XB44, B47, B49). Ten of these samples were derived from locoregional lymphnode metastases or from distant metastatic tumors. Only one sample from a primary melanoma showed a specific loss of HLA-I (B47). IFN-alpha upregulated expression of HLA-I up to 4-fold. IFN-gamma enhanced the appearance of HLA-II up to 35-fold and the expression of intercellular adhesion molecule 1 up to 40-fold. Selective loss of HLA-I allospecificities might be a major step in tumor progression.
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PMID:Higher frequency of selective losses of HLA-A and -B allospecificities in metastasis than in primary melanoma lesions. 974 Feb 47

Conflicting results have been obtained by various research groups using tyrosinase reverse transcription-polymerase chain reaction (RT-PCR) for detecting micrometastases in the blood of melanoma patients, with positive results ranging from 0 to 100% in disseminated melanoma. Methodological differences in the processing of blood samples may in part account for these discrepancies. The aim of this study was to standardize and optimize the experimental conditions for RT-PCR detection of melanoma cells in peripheral blood. We analysed the effect of different parameters of sample processing on the sensitivity of the tyrosinase RT-PCR using peripheral blood spiked with defined numbers of SKMEL28 melanoma cells. Purification of the mononuclear cell fraction using a Ficoll gradient with a density of 1.077 g/mL prior to RNA isolation gave the highest sensitivity, with the detection of two SKMEL28 cells in 5 mL of blood. In addition, the RNA isolation method and the kind of RT enzyme used had a significant impact on the sensitivity and reproducibility of tyrosinase detection, whereas variations in the PCR conditions had only a minor influence. Furthermore, we showed that amplification of MelanA in addition to tyrosinase resulted in an approximately 10% enhanced sensitivity of melanoma cell detection, whereas gp100/pMel17 and MUC18 gene products were also detected in blood from non-melanoma patients. MelanA could serve as a sensitive marker in addition to tyrosinase for detecting micrometastases.
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PMID:Increased sensitivity for the detection of malignant melanoma cells in peripheral blood using an improved protocol for reverse transcription-polymerase chain reaction. 1041 13

Conflicting results were obtained by various research groups using the tyrosinase reverse transcription polymerase chain reaction (RT-PCR) for detecting melanoma cells circulating in peripheral blood. Whereas 100% positivity was initially reported for stage IV patients, more recent investigations reported positive detection rates between 30% and 50% in patients with disseminated melanoma. While the high detection rate initially reported in metastatic melanoma may be explained by contamination problems, methodological differences in different steps of the technical procedure of RT-PCR may account for the differences reported in more recent examinations. Major differences may result from the kind of blood preparation, the RNA isolation method, the kind of RT enzyme used, and the gene targeted by PCR primers. In our experience, blood purification by a Ficoll gradient increased melanoma cell detection rates compared to RNA extraction from total blood or after erythrocyte lysis. Amplification of MelanA in addition to tyrosinase resulted in a 30% enhanced sensitivity of melanoma cell detection compared to amplification to tyrosinase alone, whereas gp100/pMel17 and MUC18 gene products were already detected in blood from nonmelanoma patients. These findings are in agreement with those of other groups. Currently, an increase in the sensitivity for detection of circulating tumour cells to more than 50% of patients with disseminated melanoma seems to be unlikely. It is interesting that between 15% and 30% positive results and sometimes more have already been obtained from patients with primary melanoma. So far, there is no data for judging the prognostic significance of the detection of circulating tumour cells in patients without clinically recognisable metastases. Our limited experience shows that staging examinations in these patients reveal no proof of macrometastasis. Therefore, it is presently unclear whether these positive findings are associated with long-term prognosis or if they merely reflect false positive findings in this highly sensitive RT-PCR technique.
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PMID:Polymerase chain reaction in the detection of circulating tumour cells in peripheral blood of melanoma patients. 1109 36

Nasal mucosa melanoma is a rare entity that may occur together with nasal melanosis. The histological and immunological features and loss of heterozygosity analysis of such lesions have not been reported to date. In the study presented here short-term cell cultures were established from the patient's melanoma and subsequent relapses. Histology, immunohistochemistry, reverse transcription-polymerase chain reaction enzyme-linked immunosorbent assay, human leukocyte antigen analysis, microdissection with subsequent polymerase chain reaction for analysis of loss of heterozygosity were used to characterize the tumour and other cells. Melanoma of the nasal cavity was found, with a surrounding proliferation of atypical melanocytes corresponding to nasal melanosis. Immunoreactivity was found for S-100, gp100, tyrosinase and MelanA protein. Loss of heterozygosity for a p16-flanking marker was found in the tumour and the melanotic cells. Short-term cell cultures expressed tyrosinase and MUC18 at the mRNA level and intercellular adhesion molecule-1 (ICAM-1) and interleukin-12 receptor at the protein level. This is the first time short-term cell cultures have been established and analysed from such a tumour. Melanoma-associated antigens were identified within the tumour. The melanoma and the melanotic cells showed loss of heterozygosity for the p16 gene, which is implicated in melanoma development. This points to a common origin in tumorigenesis. Pathways of tumour escape, such as expression of CD54 and interleukin-10, were observed. The clinical, immunological and molecular features suggest that nasal melanosis should be followed closely.
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PMID:Histological, immunological and molecular features of a nasal mucosa primary melanoma associated with nasal melanosis. 1182 61

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

Transformation of the pigment producing melanocytes into melanoma is a complex multi-step process involving the enhanced expression of various antigens considered as immunotherapeutic targets. Significant progress in melanoma research has been made over the years and has resulted in the identification of various antigens over expressed in melanoma as well as advances in immunotherapeutic treatments, which focus on modulating the immune systems response to melanoma. Despite these advances, incidences of melanoma are still on the rise thus warranting additional research in identifying new therapeutic treatments. Our focus is on developing a multivalent immunotherapeutic vaccine that targets various melanoma associated antigens. The approach focuses on the use of five primary patient derived melanoma cells (MEL-2, MEL-V, 3MM, KFM, and GLM-2, which have been characterized in this study. These cells express differential amounts of various melanoma associated antigens such as MART-1, gp100 (Pmel17), MAGE-A1 and tyrosinase as well a cell surface antigens essential for melanoma cell metastasis, such as CD146 and CD71. In addition these cells display differential in vitro migratory and invasive properties as well as have the ability to form solid tumors when implanted into BALB/c nude mice. The retention of the innate phenotype of these primary patient derived cells together with the expression of a multitude repertoire of melanoma associated antigens offers a novel opportunity to target melanoma so as to avoid immune evasion.
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PMID:Ex vivo derived primary melanoma cells: implications for immunotherapeutic vaccines. 2383 82