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: UNIPROT:P10721 (c-kit)
6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The c-kit gene encodes a transmembrane receptor that has tyrosine kinase activity. c-kit plays a role in hematopoiesis, gametogenesis, and melanogenesis. c-kit is found in melanocytes, and there is evidence that expression is lost in melanoma. We studied 85 melanocytic lesions for c-kit by immunohistochemical techniques using a monoclonal antibody. The lesions included banal nevi, junctional and compound nevi with melanocytic dysplasia, nontumorigenic radial growth phase melanoma, tumorigenic vertical growth phase melanoma, and metastatic melanoma. We found intense membrane staining in normal melanocytes and mast cells. Staining in compound nevi was strongest in junctional and superficial dermal components, whereas dermal nevi showed weak reactivity. Dysplastic nevi stained strongly, particularly in junctional cells. In melanoma, strong reactivity was most prominent in radial growth phase disease, but there was little or no staining in vertical growth phase and metastatic melanomas. In summary, c-kit protein is expressed in normal melanocytes, benign nevi, dysplastic nevi and nontumorigenic melanoma, but expression is lost in tumorigenic primary melanomas and metastases. The role of c-kit loss in advanced melanoma requires additional investigation.
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PMID:Proto-oncogene c-kit expression in malignant melanoma: protein loss with tumor progression. 931 Sep 59

Stem cell factor (SCF) is a glycoprotein growth factor produced by marrow stromal cells that acts after binding to its specific surface receptor, which is the protein encoded by the protooncogene c-kit. SCF synergizes with specific lineage factors in promoting the proliferation of primitive hematopoietic progenitors, and has been administered to expand the pool of these progenitors in cancer patients treated with high-dose chemotherapy. SCF and its c-kit receptor are expressed by some tumor cells, including myeloid leukemia, breast carcinoma, small cell lung carcinoma, melanoma, gynecological tumors, and testicular germ cell tumors. Previous studies of SCF in neuroblastoma have produced conflicting conclusions. To explore the role of SCF in neuroblastoma, we studied five neuroblastoma lines (IMR-5, SK-N-SH, SK-N-BE, AF8, and SJ-N-KP) and the neuroepithelioma line CHP-100. All lines expressed mRNA for c-kit and c-kit protein at low intensity as measured by flow cytometry, and secreted SCF in medium culture as shown by ELISA. Exogenous SCF did not modify 3H thymidine uptake in the neuroblastoma and neuroepithelioma cell lines. After 6 days' culture in the presence of anti-c-kit, the number of viable neuroblastoma cells was significantly lower than the control, and terminal deoxynucleotidyl transferase assay showed a substantial increase of apoptotic cells: The percentage of positive cells was 1-3% in the control lines, whereas in the presence of anti c-kit it varied from 29% of SK-N-BE to 92% of CHP-100. After 9 days' culture in the presence of anti-c-kit, no viable cells were detectable. These data indicate that SCF is produced by some neuroblastoma cell lines via an autocrine loop to protect them from apoptosis.
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PMID:Stem cell factor suppresses apoptosis in neuroblastoma cell lines. 935 69

In recent years the idea of using gene therapy as a modality in the treatment of diseases other than genetically inherited, monogenic disorders has taken root. This is particularly obvious in the field of oncology where currently more than 100 clinical trials have been approved worldwide. This report will summarize some of the exciting progress that has recently been made with respect to both targeting the delivery of potentially therapeutic genes to tumor sites and regulating their expression within the tumor microenvironment. In order to specifically target malignant cells while at the same time sparing normal tissue, cancer gene therapy will need to combine highly selective gene delivery with highly specific gene expression, specific gene product activity, and, possibly, specific drug activation. Although the efficient delivery of DNA to tumor sites remains a formidable task, progress has been made in recent years using both viral (retrovirus, adenovirus, adeno-associated virus) and nonviral (liposomes, gene gun, injection) methods. In this report emphasis will be placed on targeted rather than high-efficiency delivery, although those would need to be combined in the future for effective therapy. To date delivery has been targeted to tumor-specific and tissue-specific antigens, such as epithelial growth factor receptor, c-kit receptor, and folate receptor, and these will be described in some detail. To increase specificity and safety of gene therapy further, the expression of the therapeutic gene needs to be tightly controlled within the target tissue. Targeted gene expression has been analyzed using tissue-specific promoters (breast-, prostate-, and melanoma-specific promoters) and disease-specific promoters (carcinoembryonic antigen, HER-2/neu, Myc-Max response elements, DF3/MUC). Alternatively, expression could be regulated externally with the use of radiation-induced promoters or tetracycline-responsive elements. Another novel possibility that will be discussed is the regulation of therapeutic gene products by tumor-specific gene splicing. Gene expression could also be targeted at conditions specific to the tumor microenvironment, such as glucose deprivation and hypoxia. We have concentrated on hypoxia-targeted gene expression and this report will discuss our progress in detail. Chronic hypoxia occurs in tissue that is more than 100-200 microns away from a functional blood supply. In solid tumors hypoxia is widespread both because cancer cells are more prolific than the invading endothelial cells that make up the blood vessels and because the newly formed blood supply is disorganized. Measurements of oxygen partial pressure in patients' tumors showed a high percentage of severe hypoxia readings (less than 2.5 mmHg), readings not seen in normal tissue. This is a major problem in the treatment of cancer, because hypoxic cells are resistant to radiotherapy and often to chemotherapy. However, severe hypoxia is also a physiological condition specific to tumors, which makes it a potentially exploitable target. We have utilized hypoxia response elements (HRE) derived from the oxygen-regulated phosphoglycerate kinase gene to control gene expression in human tumor cells in vitro and in experimental tumors. The list of genes that have been considered for use in the treatment of cancer is extensive. It includes cytokines and costimulatory cell surface molecules intended to induce an effective systemic immune response against tumor antigens that would not otherwise develop. Other inventive strategies include the use of internally expressed antibodies to target oncogenic proteins (intrabodies) and the use of antisense technology (antisense oligonucleotides, antigenes, and ribozymes). This report will concentrate more on novel genes encoding prodrug activating enzymes, so-called suicide genes (Herpes simplex virus thymidine kinase, Escherichia coli nitroreductase, E. (ABSTRACT TRUNCATED)
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PMID:Targeting gene therapy to cancer: a review. 940 37

Germline mutations at loci encoding the transcription factor Microphthalmia (Mi), the cytokine receptor c-Kit, or its ligand Steel factor (S1) result in strikingly similar defects in mast cell and melanocyte development. Here we describe a biochemical link between Kit signalling and the activity of Mi. Stimulation of melanoma cells with S1 results in activation of MAP kinase, which in turn phosphorylates Mi at a consensus target serine. This phosphorylation upregulates Mi transactivation of the tyrosinase pigmentation gene promoter. In addition to modulating pigment production, such signalling may regulate the expression of genes essential for melanocyte survival and development. The pathway represents a new application of the general MAP kinase machinery in transducing a signal between a tissue-specific receptor at the cell surface and a tissue-specific transcription factor in the nucleus.
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PMID:MAP kinase links the transcription factor Microphthalmia to c-Kit signalling in melanocytes. 944 Jun 96

The c-kit gene product (CD117) is known to be expressed by a variety of normal human tissue cell types, including breast epithelium, germ cells, melanocytes, immature myeloid cells, and mast cells. To further characterize the expression of this antigen, 117 normal human tissues and 576 human tumors were studied by paraffin section immunohistochemistry. Varying degrees of CD117 expression were identified in various normal cells and in 53% of all tumors studied. In most cases (42% of total), CD117 expression was weak. Expression was most common in mast cell disease (100%), testicular germ cell tumors (100%), endometrial carcinomas (100%), papillary and follicular thyroid carcinomas (100%), small cell carcinomas (91%), malignant melanomas (90%), and ovarian epithelial carcinomas (87%). Strong immunoreactivity was only identified in cases of mast cell disease (11 of 11 cases), serous ovarian carcinoma (3 of 16), malignant melanoma (2 of 40), small cell lung carcinoma (one of seven), and adenoid cystic carcinoma (one of one). Although the pattern of reactivity was primarily cytoplasmic, a membrane staining pattern was seen in a subset of cases, and strong membrane staining was identified in normal mast cells and all cases of mast cell disease. The lack of tumor specificity of weak expression of this antigen limits its diagnostic utility in most cases. However, the strong membrane reactivity for CD117 identified in mast cells may be useful in the diagnosis of mast cell disorders.
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PMID:Paraffin section detection of the c-kit gene product (CD117) in human tissues: value in the diagnosis of mast cell disorders. 959 74

Melanoma cells in culture express a variety of growth factors and cytokines and some of their autocrine and paracrine roles have been investigated. However, less information is available on the potential dynamic changes in expression of these molecules on cells during melanoma development and progression in situ. Using immunohistochemistry, we tested 40 nevi and primary and metastatic melanoma lesions for the expression of 10 growth factors and cytokines and the respective receptors representing 10 cell surface molecules. Nevi and thin (< 1 mm) primary melanomas showed little expression of ligands except weak reactivity of tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), interleukin-8 (IL-8) and reactivity of TGF-betaR and c-kit. Marked up-regulation of growth factors, cytokines and receptor expression was observed in thick (> 1 mm) primary melanomas, which were stained with polyclonal or monoclonal antibodies (MAbs) for IL-1alpha, IL-1beta, IL-6, IL-8, TNF-alpha, TGF-beta, granulocyte-macrophage colony-stimulating factor (GMCSF) and stem cell factor (SCF), but not IL-2. Metastases showed similar expression patterns except that SCF was absent. Co-expression of ligand and receptor was observed for TGF-beta, GM-CSF and IL-6, suggesting an autocrine role for these ligands. TNF-alpha appears to be a marker of benign lesions; IL-6 and IL-8 expression is associated with biologically early malignancy; TGF-beta, GM-CSF and IL-1alpha are highly expressed in biologically late lesions; and TNF-beta is an apparent marker of metastatic dissemination. Our results indicate that melanoma cells utilize cascades of growth factors and cytokines for their progression.
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PMID:Immunohistochemical evidence of cytokine networks during progression of human melanocytic lesions. 1009 49

Malignant melanomas do not uniformly retain expression of melanocytic gene products-an observation associated with diagnostic dilemmas. Microphthalmia transcription factor (Mitf) is a melanocytic nuclear protein critical for the embryonic development and postnatal viability of melanocytes. It serves as a master regulator in modulating extracellular signals, such as those triggered by alpha-MSH and c-Kit ligand. Because of its central role in melanocyte survival and to assess its potential use as a histopathological marker for melanoma, Mitf expression was examined in histologically confirmed human melanoma specimens. Western blot analysis of melanoma cell lines revealed consistent expression of two Mitf protein isoforms differing by MAP kinase-mediated phosphorylation. In a series of 76 consecutive human melanoma surgical specimens, 100% stained positively for Mitf with a nuclear pattern of reactivity. In a side-by-side comparison, Mitf staining was positive in melanomas that failed to stain for either HMB-45 or S-100, the most common currently used melanoma markers. Of 60 non-melanoma tumors, none displayed nuclear Mitf staining and two displayed cytoplasmic staining. Although Mitf does not distinguish benign from malignant melanocytic lesions, for invasive neoplasms it appears to be a highly sensitive and specific histopathological melanocyte marker for melanoma.
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PMID:Microphthalmia transcription factor. A sensitive and specific melanocyte marker for MelanomaDiagnosis. 1048 31

The melanoma cell adhesion molecule was identified as a human melanoma-associated antigen that increases in expression as tumors increase in thickness and begin to acquire metastatic potential. Clinical and experimental evidences suggest that the development of metastatic capacity might be the consequence of increased melanoma cell adhesion molecule expression. The mechanisms for upregulation of the melanoma cell adhesion molecule during melanoma progression are, however, still poorly understood. In this study, we show that melanoma cell adhesion molecule expression is tightly regulated at the transcriptional level. Using a combination of CAT reporter assays and semiquantitative reverse transcriptase-polymerase chain reaction, we observed that cyclic adenosine monophosphate significantly increases transcription of the melanoma cell adhesion molecule in nonmetastatic melanoma cells. In metastatic cells, transcription of the gene was constitutive and could not be further increased by cyclic adenosine monophosphate. On the other hand, melanoma cell adhesion molecule promoter activity was impeded upon treatment with phorbol esters or in the presence of stem cell factor, a phenomenon which was protein kinase C-dependent. Promoter-deletion studies demonstrated that the first 196 nt of the melanoma cell adhesion molecule promoter region are sufficient to get full expression in metastatic melanoma cells. This fragment contains five binding sites for the transcription factor Sp1 and DNA mobility shift experiments showed direct binding of Sp1 to the promoter. In conclusion, our results indicate that Sp1 is sufficient to drive constitutive melanoma cell adhesion molecule expression in metastatic melanoma cells. In nonmetastatic cells, however, melanoma cell adhesion molecule expression is repressed and we speculate that stem cell factor/c-Kit signaling might be responsible for the control of melanoma cell adhesion molecule synthesis, and thus, perhaps, of melanoma progression and metastasis.
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PMID:Regulation of the melanoma cell adhesion molecule gene in melanoma: modulation of mRNA synthesis by cyclic adenosine monophosphate, phorbol ester, and stem cell fFactor/c-kKit signaling. 1057 24

Stem cell factor (SCF), the ligand for c-Kit, is known to regulate developmental and functional processes of haematopoietic stem cells, mast cells and melanocytes. Two different splice variants form predominantly soluble (sSCF or SCF-1) and in addition some membrane-bound SCF (mSCF or SCF-2). In order to explore the prognostic significance of these molecules in melanoma, total SCF, SCF splice variants and c-Kit expression were studied in normal skin melanocytes and in 11 different melanoma cell lines, using reverse transcription polymerase chain reaction, immunocytochemistry and enzyme-linked immunosorbent assay. Nine of the 11 melanoma cell lines expressed SCF-1 mRNA, only two of them SCF-2, and these two also SCF-1. Coexpression of both SCF-1 and c-Kit was noted in five cell lines, and only one cell line as well as normal melanocytes expressed both SCF-1 and SCF-2 as well as c-Kit. Corresponding results were obtained on immunocytochemical staining. Of three exemplary melanoma cell lines studied, two expressing SCF mRNA also released SCF spontaneously and on stimulation, whereas the line lacking SCF and c-kit mRNA (SK-Mel-23) failed to do so. These data demonstrate thus that melanoma cell lines, particularly those known to metastasize in vivo, lose the ability to express SCF-2 mRNA, suggesting that this molecule may serve, next to c-Kit, as a prognostic marker for malignant melanoma.
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PMID:Expression of SCF splice variants in human melanocytes and melanoma cell lines: potential prognostic implications. 1078 May 26

Migrating cells are polarized with a protrusive lamella at the cell front followed by the main cell body and a retractable tail at the rear of the cell. The lamella terminates in ruffling lamellipodia that face the direction of migration. Although the role of actin in the formation of lamellipodia is well established, it remains unclear to what degree microtubules contribute to this process. Herein, we have studied the contribution of microtubules to cell motility by time-lapse video microscopy on green flourescence protein-actin- and tubulin-green fluorescence protein-transfected melanoma cells. Treatment of cells with either the microtubule-disrupting agent nocodazole or with the stabilizing agent taxol showed decreased ruffling and lamellipodium formation. However, this was not due to an intrinsic inability to form ruffles and lamellipodia because both were restored by stimulation of cells with phorbol 12-myristate 13-acetate in a Rac-dependent manner, and by stem cell factor in melanoblasts expressing the receptor tyrosine kinase c-kit. Although ruffling and lamellipodia were formed without microtubules, the microtubular network was needed for advancement of the cell body and the subsequent retraction of the tail. In conclusion, we demonstrate that the formation of lamellipodia can occur via actin polymerization independently of microtubules, but that microtubules are required for cell migration, tail retraction, and modulation of cell adhesion.
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PMID:Actin-dependent lamellipodia formation and microtubule-dependent tail retraction control-directed cell migration. 1098 96


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