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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A case of melanotic neuroectodermal tumor of infancy arising from the transverse sinus is presented. The tumor was located on the outer surface of the dura and extended extracranially through the occipitomastoid suture. Two cell populations were observed: pigmented melanocyte-like cells and small neuroblast-like cells. Ultrastructural analysis revealed epithelial tumor cells and melanosomes at various stages. Expression of melanotransferrin messenger RNA transcripts within the tumor tissue was observed using a reverse transcriptase-polymerase chain reaction method in addition to immunohistological studies. The positive expression of melanotransferrin confirmed that this melanotic neuroectodermal tumor was derived from neural crest cells.
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PMID:Melanotic neuroectodermal tumor of infancy: a molecular approach to diagnosis. Case report. 778 33

Mucins, including MUC-1, are generally considered to be products of epithelial tissues and of their tumors. To examine the possible expression of MUC-1 in other cell types, a panel of human epithelial and non-epithelial tumor cell lines was studied by reverse transcriptase polymerase chain reaction (RT-PCR), Northern blot analysis, immunocytology and radioimmunoprecipitation. Using the highly sensitive RT-PCR method, products corresponding to the non-repetitive 5' and 3' MUC-1 sequences were detected in all the cell lines examined. Amplified products lacking the tandem repeat region of MUC-1, including a new short form (designated MUC-1/Z) different from the previously reported MUC-1/Y protein, were also detected in most cell lines tested. Northern blot analysis, using a probe to the variable number tandem repeat (VNTR) region, confirmed the presence of MUC-1 mRNA in the astrocytoma, melanoma and neuroblastoma cell lines studied. MUC-1 protein was detected by immunocytology in these cell lines using monoclonal antibody (MAb) 139H2. Immunoprecipitation analysis with [3H]-glucosamine-labeled cell lysates and MAb 139H2 or an antibody to the cytoplasmic domain, CT-1, detected MUC-1 protein in 2 epithelial cell lines, an astrocytoma cell line (SK-MG-4) but not in the melanoma and neuroblastoma cell lines studied. Northern blot analysis using a probe to the 3' end of MUC-1 mRNA, confirmed the presence of MUC-1 mucin and also identified short products corresponding to the size of the short variant forms. Protein products corresponding to the MUC-1/Y and MUC-1/Z variant forms were not observed using either [3H]-glucosamine-labeled OVCAR-3 cells or [3H]-amino acid-labeled MCF-7 cells and either CT-1 antibody or MAb 232A1, detecting an epitope to the C-terminal region. Thus, depending on the sensitivity of the assay used, varying amounts of MUC-1 mRNA and protein could be detected in non-epithelial tumor cell lines. Although the amounts of MUC-1 in these cell lines are much lower than in carcinomas, it is possible that MUC-1 mucin serves a similar function in non-epithelial as in epithelial cells. The possible role of MUC-1/Y and MUC-1/Z variant forms in these cell lines is not understood.
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PMID:Comparison of MUC-1 mucin expression in epithelial and non-epithelial cancer cell lines and demonstration of a new short variant form (MUC-1/Z). 921 28

Disseminated epithelial tumor cells have been detected in the bone marrow and blood of cancer patients by means of immunocytochemical or immunofluorescent staining of cytocentrifuge slides, multiparameter flow cytometry, and reverse transcriptase-polymerase chain reaction. However, it is hardly possible using such methods to detect tumor cells at a frequency below 10(-6). To increase the sensitivity of these detection techniques we have developed a new technology for the enrichment of disseminated epithelial tumor cells from hematopoietic cell samples by high-gradient magnetic cell sorting (MACS). Cells are permeabilized and fixed and carcinoma cells are magnetically labeled specifically with an anti-cytokeratin 8 monoclonal antibody (mAb) directly conjugated to superparamagnetic microbeads. Magnetically labeled cells are enriched on high-gradient magnetic columns. Tumor cells are detected in the enriched cell fraction by flow cytometry, fluorescence microscopy, or immunocytochemisty. In this study we demonstrated the method using a model system in which five to 5,000 cells from a breast cancer cell line were seeded into blood cell samples from a healthy donor containing 1.2 x 10(8) leukocytes. Tumor cells were 10,477+/-4242 (n=25)-fold magnetically enriched, and 57.7%+/-16.9% (n=33) of the initially seeded tumor cells were recovered. Applying the method to 20-40 mL blood samples from patients with advanced carcinomas of the breast, prostate, colon, rectum, or lung, we were able to detect between one and 6.8 x 10(4) cytokeratin-expressing tumor cells in 21 of 34 patients. This corresponds to frequencies of tumor cells between 6.8 x 10(-9) and 1.1 x 10(-3) among nucleated cells in the original sample. Enriched tumor cells were further analyzed for expression of tissue-specific and prognostic markers such as breast mucin glycoproteins, erbB2, and CD44v6 for additional characterization and to confirm their tumor origin. The technique described could become a valuable tool for the quantification and molecular characterization of metastatic carcinoma cells in hematopoietic tissue, and may ultimately prove useful in the diagnosis, prognosis, and monitoring of patients with carcinoma.
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PMID:Immunomagnetic enrichment of disseminated epithelial tumor cells from peripheral blood by MACS. 950 22

Cytokines appear to play an important role in the development and progression of epithelial tumors. Cultured normal human thyroid follicular cells constitutively release high levels of interleukin-6 (IL-6) and IL-8, together with low to moderate levels of transforming growth factor-alpha (TGF-alpha) and TGF-beta. IL-6 appears to play multiple functions in thyroid physiology and disease. Because certain data indicate an inverse relationship between IL-6 production and epithelial tumor aggressiveness, we used both tissue culture methods and histochemical techniques to search for possible alterations of cytokine expression in thyroid carcinomas. As compared to cultures from normal tissue and well-differentiated carcinoma, production of IL-6 was strongly down-regulated in cultures derived from undifferentiated carcinoma. In contrast, levels of IL-8, TGF-alpha, and TGF-beta produced by neoplastic TFC were similar to those produced by normal cells. Actually, production of TGF-alpha was slightly enhanced in cultures from well-differentiated carcinoma. Immunoassay results were confirmed by reverse transcriptase-PCR analysis. Immunohistochemistry of human thyroid carcinomas (n = 99) and normal thyroid tissue (n = 85) showed that immunoreactive IL-6 was strongly diminished in undifferentiated forms (n = 34) and slightly reduced in well-differentiated carcinoma (n = 65). In agreement with the in vitro results, TGF-alpha expression was significantly increased in neoplastic thyrocytes, as compared to their normal counterpart. The results indicate that, as in the mammary and salivary glands, down-regulation of IL-6 expression may represent a marker of undifferentiated thyroid carcinoma.
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PMID:Reduced expression of interleukin 6 in undifferentiated thyroid carcinoma: in vitro and in vivo studies. 951 26

We have developed a new assay, ISET (isolation by size of epithelial tumor cells), which allows the counting and the immunomorphological and molecular characterization of circulating tumor cells in patients with carcinoma, using peripheral blood sample volumes as small as 1 ml. Using this assay, epithelial tumor cells can be isolated individually by filtration because of their larger size when compared to peripheral blood leukocytes. ISET parameters were defined using peripheral blood spiked with tumor cell lines (HepG2, Hep3B, MCF-7, HeLa, and LNCaP). ISET can detect a single, micropipetted tumor cell, added to 1 ml of blood. We also demonstrate that fluorescence in situ hybridization can be used to perform chromosomal analyses on tumor cells collected using ISET. Polymerase chain reaction-based genetic analyses can be applied to ISET-isolated cells, and, as an example, we demonstrate homozygous p53 deletion in single Hep3B cells after filtration and laser microdissection. Finally, we provide evidence for the in vivo feasibility of ISET in patients with hepatocellular carcinoma undergoing tumor resection. ISET, but not reverse transcriptase-polymerase chain reaction, allowed analysis of cell morphology, counting of tumor cells, and demonstration of tumor microemboli spread into peripheral blood during surgery. Overall, ISET constitutes a novel approach that should open new perpectives in molecular medicine.
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PMID:Isolation by size of epithelial tumor cells : a new method for the immunomorphological and molecular characterization of circulatingtumor cells. 1062 54

The aim of this study is the counting and the immunomorphological and molecular characterization of circulating tumor cells (CTCs) by the isolation by size of epithelial tumor cells (ISET) method in the peripheral blood of patients with breast cancer. An evaluation of the method's ability to reveal the presence of occult carcinoma cells in blood of a patient with breast cancer was performed and the results compared with those obtained by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay for the evaluation of cytokeratin-19 (CK-19) mRNA expression. The feasibility of molecular analysis of CTCs after laser microdissection of filters used in ISET was illustrated, referring to HER-2 amplification. Blood samples drawn from 44 patients with breast cancer were preoperatively analyzed by ISET. From the same samples, total RNA was extracted and submitted to quantitative real-time RT-PCR for the detection of CK-19 mRNA-positive cells using TaqMan technology. HER-2 amplification was measured by real-time RT-PCR on DNA extracted from cells recovered by laser microdissection from 7 selected ISET-positive filters. Of 44 samples, 12 (27%) showed the presence of epithelial cells on the filter (mean +/- SE: 8.5 +/- 2.4 cells per milliliter of blood). A statistically significant agreement (P = .001) was observed between real-time RT-PCR results and those obtained by ISET. With regard to HER-2 amplification, a good correspondence was found between the results obtained from microdissected CTCs and those obtained using DNA extracted from the primary tumor (R = 0.918; P < .01), as well as the immunohistochemistry results. The ISET method allows for the collection of breast carcinoma cells by filtration despite their smaller dimension relative to other carcinoma cell types. The sensitivity and specificity of the method is comparable with those obtained using the quantitative real-time RT-PCR assay for the evaluation of CK-19 mRNA expression. Moreover, the laser microdissection technique allows for the recovery of nucleic acids for further molecular analysis and CTC characterization.
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PMID:Isolation by size of epithelial tumor cells in peripheral blood of patients with breast cancer: correlation with real-time reverse transcriptase-polymerase chain reaction results and feasibility of molecular analysis by laser microdissection. 1673 12

Thymoma is a thymic epithelial neoplasm which induces T cell development. However, the frequency of mature CD4(+) T cells in thymomas is lower than in normal thymi. Recently, CD4/CD8 lineage commitment has been elucidated in animal model. The zinc finger transcription factor Th-POK is a critical factor to CD4(+) T cell development in CD4/CD8 lineage commitment, whereas CD8(+) T cell development requires the transcription factor Runx3. These factors antagonize in CD4/CD8 lineage commitment. In this study, we examined Th-POK and Runx3 mRNA expression in the T cell subsets of human normal thymus and thymoma. A quantitative reverse transcriptase-polymerase chain reaction examination revealed that Th-POK expression in normal thymi was higher in the CD4(+)CD8(-) subset than in the CD4(+)CD8(+) and CD4(-)CD8(+) subsets. In thymomas, Th-POK expression in the CD4(+)CD8(-) subset was significantly lower than that in normal thymi, and was significantly correlated with the proportion of CD3(+) cells in the CD4(+)CD8(-) subset. However, Th-POK expressions of the CD3(+)CD4(+)CD8(+) and CD3(+)CD4(+)CD8(-) subsets were not impaired in thymomas compared to normal thymi. These results suggest that thymoma neoplastic epithelial cells can induce Th-POK expression similarly to the normal thymic epithelial cells. In addition, there was no significant difference in Runx3 expression between normal thymi and thymomas. Therefore, CD4/CD8 lineage commitment dependent on Th-POK and Runx3 system seems to be working even in the neoplastic environment formed by human thymomas.
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PMID:Regulation of Th-POK and Runx3 in T cell development in human thymoma. 1988 37

Condyloma acuminatum (CA) is a benign epithelial tumor caused by infection with human papillomaviruses (HPVs) and characterized by abnormal cell proliferation. Cellular caspase-8 (FLICE)-like inhibitory protein (c-FLIP) was originally identified as an inhibitor of death-receptor signaling through competition with caspase-8 for recruitment to FAS-associated via death domain (FADD). More recently, it has been determined that c-FLIP is associated with the survival and proliferation of T cells and keratinocytes. The aim of this work was to study the expression of c-FLIP in CA and its relationship with keratinocyte proliferation. Immunoperoxidase staining methods were applied to analyze the location and expressions of both c-FLIP and proliferating cell nuclear antigens (PCNA) in 34 CA and 16 normal foreskin tissues. Semiquantitative reverse transcriptase-polymerase chain reactions (RT-PCR) and western blotting were performed to further identify the expression of c-FLIP in CA. c-FLIP expression at both mRNA and protein level was significantly higher in CA than normal foreskin. c-FLIP expression was highly correlated with the PCNA labeling index (LI) in CA. We concluded that c-FLIP overexpression might take part in keratinocyte proliferation in CA.
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PMID:Increased expression of cellular FLICE/caspase-8 inhibitory protein in condyloma acuminatum. 2168 Feb 88

The human LINE-1 (or L1) element is a non-LTR retrotransposon that is mobilized through an RNA intermediate by an L1-encoded reverse transcriptase and other L1-encoded proteins. L1 elements remain actively mobile today and continue to mutagenize human genomes. Importantly, when new insertions disrupt gene function, they can cause diseases. Historically, L1s were thought to be active in the germline but silenced in adult somatic tissues. However, recent studies now show that L1 is active in at least some somatic tissues, including epithelial cancers. In this review, we provide an overview of these recent developments, and examine evidence that somatic L1 retrotransposition can initiate and drive tumorigenesis in humans. Recent studies have: (i) cataloged somatic L1 activity in many epithelial tumor types; (ii) identified specific full-length L1 source elements that give rise to somatic L1 insertions; and (iii) determined that L1 promoter hypomethylation likely plays an early role in the derepression of L1s in somatic tissues. A central challenge moving forward is to determine the extent to which L1 driver mutations can promote tumor initiation, evolution, and metastasis in humans.
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PMID:The Role of Somatic L1 Retrotransposition in Human Cancers. 2856 51

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