Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.10.3.1 (tyrosinase)
9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The recent identification of tumor-associated antigens and tumor-associated antigen-derived peptide epitopes recognized by cytolytic T lymphocytes (CTLs) in the context of major histocompatibility complex (MHC) class I molecules has prompted the development of peptide-based vaccines for the treatment of human cancers, particularly melanoma. The design of such clinical protocols requires an understanding of the inherent immunogenicity of the peptide(s) and a choice of a facilitating adjuvant promoting cellular immunity against these peptides. We have evaluated the abilities of a series of defined synthetic peptide epitopes derived from MART-1/Melan-A, gp100, tyrosinase, and MAGE-3 or unfractionated peptides naturally presented by melanoma MHC molecules to elicit HLA-A2-restricted and melanoma-reactive CTLs from the peripheral blood of normal donors or patients with metastatic melanoma. Autologous peripheral blood dendritic cells (DCs), which were easily generated from all donors when cultured in the presence of recombinant human interleukin-4 and recombinant human granulocyte-macrophage colony-stimulating factor were pulsed with melanoma peptides and used to "prime" and/or "boost" CTL cultures in vitro. Our results suggest that antimelanoma CTLs may be reproducibly generated in short-term in vitro cultures in this manner using either a subset of the defined synthetic peptides (MART-1/Melan-A27-35, MART-1/Melan-A32-40, gp100(280-288), tyrosinase368-376, and MAGE-3(271-279)) or unfractionated peptides (containing both idiotypic and shared melanoma epitopes) derived from freshly isolated autologous melanoma lesions. These in vitro data support the use of autologous DCs prepulsed with such peptides as an appropriate antigen adjuvant delivery system in melanoma peptide-based vaccines.
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PMID:Autologous human dendriphages pulsed with synthetic or natural tumor peptides elicit tumor-specific CTLs in vitro. 955 67

It has recently been shown that tumor-associated antigens (TAAs) can evoke tumor-specific T-cell-defined immune responses in cancer patients, thereby offering the possibility of treating patients with such antigens. To develop T-cell-based immunotherapeutic approaches for renal cell carcinoma (RCC), we studied the mRNA expression profile of the TAAs RAGE-1, tyrosinase, MAGE-1, MAGE-2, NY-ESO-1, Melan-A/MART-1, glycoprotein (gp) 75, gp100, beta-catenin, PRAME, and MUM-1 in 14 human RCC cell lines and in tissue specimens of 37 primary RCCs, 2 related metastases, and 33 specimens of normal renal epithelium. Reverse transcription-PCR was performed with TAA-reactive primers, and the specificity of the PCR products was confirmed by Southern blot and/or direct sequencing. PRAME (10 of 14 cell lines), RAGE-1 (7 of 14 cell lines), and gp75 (4 of 14 cell lines) antigens were expressed in a high percentage of RCC cell lines, although the level of TAA expression varied among the different RCC cell lines. However, low levels of TAA expression in RCC cells are sufficient for recognition by TAA-specific CTLs. Transcription of tyrosinase, Melan-A/MART-1, MAGE-1, MAGE-2, NY-ESO-1, gp100, beta-catenin, and MUM-1 was not detected in any RCC cell line. Approximately 50% of surgically removed neoplasias expressed at least one TAA. RAGE-1 mRNA expression was found in 8 of 39 (21%) RCC samples, PRAME mRNA expression was found in 15 of 39 (40%) RCC samples, and gp75 mRNA expression was found in 4 of 39 (11%) RCC samples, but the expression levels of these TAAs were heterogeneous in the different RCC lesions. One RCC specimen expressed MAGE-2, whereas transcription was not detected in any RCC specimen for MAGE-1, NY-ESO-1, tyrosinase, Melan-A/MART-1, gp100, beta-catenin, and MUM-1. The normal kidney epithelium samples were negative for any TAA tested. Thus, RAGE-1, PRAME, and gp75 expression is found with a different frequency in surgically removed lesions and in RCC cell lines, suggesting that a subgroup of RCC patients could be selected for immunotherapeutic strategies that may benefit from immunization against the RAGE-1, gp75, and/or PRAME antigens. However, additional targets for T-cell-based immunotherapy of RCC have yet to be identified.
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PMID:Heterogeneous expression of the tumor-associated antigens RAGE-1, PRAME, and glycoprotein 75 in human renal cell carcinoma: candidates for T-cell-based immunotherapies? 975 17

We identified circulating CD8+ T-cell populations specific for the tumor-associated antigens (TAAs) MART-1 (27-35) or tyrosinase (368-376) in six of eleven patients with metastatic melanoma using peptide/HLA-A*0201 tetramers. These TAA-specific populations were of two phenotypically distinct types: one, typical for memory/effector T cells; the other, a previously undescribed phenotype expressing both naive and effector cell markers. This latter type represented more than 2% of the total CD8+ T cells in one patient, permitting detailed phenotypic and functional analysis. Although these cells have many of the hallmarks of effector T cells, they were functionally unresponsive, unable to directly lyse melanoma target cells or produce cytokines in response to mitogens. In contrast, CD8+ T cells from the same patient were able to lyse EBV-pulsed target cells and showed robust allogeneic responses. Thus, the clonally expanded TAA-specific population seems to have been selectively rendered anergic in vivo. Peptide stimulation of the TAA-specific T-cell populations in other patients failed to induce substantial upregulation of CD69 expression, indicating that these cells may also have functional defects, leading to blunted activation responses. These data demonstrate that systemic TAA-specific T-cell responses can develop de novo in cancer patients, but that antigen-specific unresponsiveness may explain why such cells are unable to control tumor growth.
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PMID:Characterization of circulating T cells specific for tumor-associated antigens in melanoma patients. 1037 7

While tumor-associated antigen (TAA)-specific CD8(+) T lymphocytes have been detected in metastatic melanoma patients, immune response in early disease phases has not yet been carefully evaluated. We looked for circulating cytotoxic T lymphocytes (CTL) directed against Melan-A / MART1, tyrosinase, gp100 and MAGE-3 antigens in patients with a diagnosis of primary cutaneous melanoma by using fluorescent HLA-A2 tetramers. In five out of six cases high numbers of CD8(+)/tetramer(+) cells could be detected by flow cytometry, and in four patients lymphocyte populations specific for two different melanoma antigens (Melan-A/MART1 and tyrosinase) were contemporaneously present. The TAA-specific cells could represent as much as 1/220 T lymphocytes in the circulating CD8(+) population. When tetramers were used to monitor the in vitro expansion of TAA-specific CTL precursors upon antigen-specific stimulation, a diverse expansion potential was evidenced in CTL from the different donors and, more strikingly, in CTL specific for the different TAA. Melan-A/MART1-specific CTL clones derived from two patients exhibited a broad range of avidity. Only the highest avidity clones, representing about 50 % of the cases analyzed, were tumor specific. By correlating tetramer staining with clone avidity, we found that tetramer fluorescence intensity could represent a good indicator of TCR affinity, but not of overall clone avidity.
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PMID:Diverse expansion potential and heterogeneous avidity in tumor-associated antigen-specific T lymphocytes from primary melanoma patients. 1118 Jan 5

Among a number of human tumor antigens identified using the serological analysis of recombinant cDNA expression libraries (SEREX), only MAGE-1, tyrosinase, and NY-ESO-1 have been reported to be immunogenic tumor antigens that have the potential to elicit both humoral and cellular immunity. In this study, we determined whether our SEREX-defined pancreatic cancer antigens could be recognized by CTL, and report that one SEREX-defined antigen, coactosin-like protein (CLP), encoded cellular epitopes recognized by HLA-A2-restricted and tumor-reactive CTL. Three CLP peptides at positions 15-24, 57-65, and 10-113 possessed the ability to induce HLA-A2-restricted and tumor-reactive CTL from the PBMC of cancer patients. Subsequently, humoral responses to these peptides were investigated. IgG antibodies specific to the CLP 15-24, 57-65, and 104-113 peptides were detected in sera from 12, 0, and 12 of 12 cancer patients tested, and were also found in 5, 0, and 0 of 9 healthy donors, respectively. IgE antibodies specific to these peptides were also detected in sera from certain cancer patients and healthy donors. Since peptide-specific IgE was detected, type-I allergy to these peptides was tested. Unexpectedly the CLP 57-65 peptide, to which IgE was found in only 2 healthy donors, but not the other two peptides, was found to elicit an immediate-type hypersensitivity in all 10 healthy volunteers tested. These results indicate that identical antigenic peptides can be recognized by both cellular and humoral immune systems to a tumor-associated antigen. The CLP 15-24 and 104-113 peptides might be appropriate vaccine candidates for peptide-based immunotherapy of HLA-A2(+) cancer patients.
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PMID:Cellular and humoral immune responses to a human pancreatic cancer antigen, coactosin-like protein, originally defined by the SEREX method. 1187 Jun 27

A specific cellular immune response directed against a panel of three defined tumor-associated antigen (TAA) epitopes was induced in metastatic melanoma patients by a prime-boost strategy taking advantage of an innovative recombinant vaccinia virus as evaluated by quantitative assessment of cytotoxic T lymphocytes (CTLs) with corresponding specificity. The immunization protocol consisted of the administration of psoralen-UV-treated and replication-incompetent recombinant vaccinia virus encoding the three immunodominant HLA-A*0201-restricted epitopes Melan-A(27-35), gp100(280-288), and tyrosinase(1-9) together with two costimulatory molecules, B7.1 and B7.2, in the context of systemic granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment. Boosts were subsequently applied with corresponding synthetic nonapeptides and GM-CSF. Specific CTL induction was assessed by tetramer staining and CTL precursor (CTLp) frequency evaluation. Within 12 days of injection of the recombinant vector, cytotoxic T cell responses specific for engineered epitopes were detectable in three of three patients. During the vaccination treatment, antigen-specific CTLp frequencies exceeding 1:10,000 peripheral CD8(+) T cells could be observed. Tetramer staining also revealed significant increases in specific CD8(+) T cell numbers. We conclude that active specific antitumor vaccination can raise a concurrent and specific cellular immune response against a panel of molecularly defined antigens, thereby increasing the chance of an immune hit against neoplastic cells with heterogeneous antigen expression. Data from this study emphasize the potency of a recombinant vaccinia virus vector encoding multiple minigenes and costimulatory molecules in the context of exogenously administered GM-CSF. Clinical effectiveness of this immunologically active protocol should therefore be explored in appropriately selected groups of patients.
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PMID:Rapid induction of specific cytotoxic T lymphocytes against melanoma-associated antigens by a recombinant vaccinia virus vector expressing multiple immunodominant epitopes and costimulatory molecules in vivo. 1187 34

We performed a phase I/II clinical trial in metastatic melanoma patients with an ultraviolet (UV)-inactivated nonreplicating recombinant vaccinia virus enabling the expression, from a single construct, of endoplasmic reticulum-targeted HLA-A0201-restricted Melan-A/MART-1(27-35), gp100(280-288), and tyrosinase(1-9) epitopes, together with CD80 and CD86 costimulatory proteins. Corresponding soluble peptides were used to boost responses and granulocyte-macrophage colony-stimulating factor was used as systemic adjuvant. Safety and immunogenicity, as monitored with in vitro-restimulated peripheral blood mononuclear cells by cytotoxic T lymphocyte precursor (CTLp) frequency analysis and tetramer staining, were specifically addressed. Of 20 patients entering the protocol, 2 had to withdraw because of rapidly progressing disease. Immune responses were evaluated in 18 patients (stage III, n = 5; stage IV, n = 13) and increases in specific CTLp frequencies were observed in 15. In 16 patients responsiveness against all 3 antigens could be analyzed: 7 (43%), including all stage III cases, showed evidence of induction of CTLs specific for the three epitopes, and 2 (12%) and 4 (25%), respectively, showed reactivity against two or one tumor-associated antigen. In three stage IV patients no specific CTL reactivity could be induced. Increases in CTLp frequency were detected mostly after viral vaccine injections. However, in a majority of patients final CTLp levels were comparable to initial levels. Tetramer characterization of Melan-A/MART-1(27-35)-specific CTLs during the protocol also suggested preferential expansion after recombinant virus administration. Vector-specific humoral responses, frequently undetectable in stage IV patients, did not appear to prevent tumor-associated antigen-specific CTL induction. Aside from a single occurrence of transient grade 3 leukopenia, no major clinical toxicity was reported. Seventeen of 18 patients completed the 3-month trial (one patient died before the last delayed-type hypersensitivity test). Three displayed regression of individual metastases, seven had stable disease, and progressive disease was observed in seven patients. This is the first report on the administration of a UV-inactivated recombinant vaccinia virus coexpressing five transgenes in cancer patients. The results described here, in terms of safety and immunogenicity, support the use of this reagent in active specific immunotherapy.
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PMID:Phase I/II clinical trial of a nonreplicative vaccinia virus expressing multiple HLA-A0201-restricted tumor-associated epitopes and costimulatory molecules in metastatic melanoma patients. 1457 12

Previous studies have analyzed transfer of RNA-encoded tumor-associated antigens (TAAs) into immature dendritic cells (DCs) because of their exceptional ability to internalize antigens. Concerns have been raised regarding the use of immature DCs in clinical studies because of their capacity to tolerize T cells. Therefore, we focused on optimizing RNA transfer into mature DCs using the method of electroporation and obtained high protein expression in 90% of mature DCs. Particular emphasis was placed on quantifying RNA transfer. Reconstitution of peptide-MHC (pMHC) ligands on RNA-pulsed DCs was measured with the help of effector-memory cytotoxic T lymphocytes (CTLs) specific for the melanoma-associated antigens tyrosinase and mutated cyclin-dependent kinase 4. In contrast to single-species RNA, transfer of native tumor-derived RNA or amplified tumor RNA into DCs resulted in very low or no capacity to reactivate these CTLs. A correlation was found between TAA message levels in tumor-derived RNA and pMHC ligand reconstitution on DCs. These results demonstrate that even TAAs with highly immunogenic mutated epitopes are not necessarily transferred when tumor-derived RNA is transfected into the DCs, thereby resulting in a lack of DC capacity to reactivate some preexisting effector-memory CTLs.
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PMID:RNA transfer by electroporation into mature dendritic cells leading to reactivation of effector-memory cytotoxic T lymphocytes: a quantitative analysis. 1592 59

Tumor cells that show downregulation of their tumor-associated antigens (TAAs) may be able to escape immune-mediated elimination. Therefore, efficient vaccine strategies attempt to target multiple TAAs simultaneously. This is easily achieved in dendritic cell (DC)-based vaccines by introducing antigens in the form of RNA. Although insufficient message may hinder adequate expression of individual TAAs when using total-tumor RNA, high amounts of individual RNAs as pools yield DCs presenting high numbers of specific peptide-major histocompatibility complex ligands with epitopes derived from different TAAs. We used the transfer of RNAs encoding the well-defined melanoma TAAs tyrosinase, Melan-A, CDK4mut, gp100, SNRP116mut, and GPNMBmut to characterize DCs at the levels of transfected RNA, expressed protein and peptide-major histocompatibility complex ligand presentation. TAA-encoding RNA was rapidly degraded in the DCs, allowing only a single surge in protein expression shortly after transfection. We compared the functional capacity of DCs transfected with pools of 3 versus 6 RNAs. Whereas functional assays demonstrated a decrease in stimulatory capacity of DCs transfected with a pool of 3 RNAs by only 30% as compared with single RNAs, a 60% loss was seen with 6 RNAs. We conclude that larger RNA pools result in diminished presentation of individual epitopes and suggest that smaller pools of RNA be transfected into separate DC populations which are then pooled to create multiplex vaccines.
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PMID:Inhibitory effect of RNA pool complexity on stimulatory capacity of RNA-pulsed dendritic cells. 1815 12

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


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