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

---

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

The product of the protooncogene c-kit is the receptor for the hematopoietic cytokine stem cell factor (SCF). C-kit is expressed on leukemic cells of the erythroid, myeloid, and mast-cell lineage and SCF has a proliferative effect on some of these cells. The role of SCF and c-kit in lymphoid malignancies is much less clear. Here we review the role of c-kit in normal lymphopoiesis and summarize its role in lymphoid malignancies. C-kit is expressed in normal lymphopoiesis and its ligand SCF synergizes with IL-7 to enhance the proliferation of B- and T-cell progenitors. In malignant lymphopoiesis, c-kit can also be expressed in B and T-lymphoblastic cells from children with non Hodgkin's lymphoma (NHL) or acute lymphoblastic leukemia (ALL) when analyzed by the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). While c-kit receptors were detected by flow cytometric (FCM) analysis on about 40% of fresh T-lymphoblastic biopsy tumor cell preparations or T-lymphoblastic cell lines, no receptors were detected on B-lymphoblastic fresh cells or cell lines from children with B-ALL or Burkitt's lymphoma (BL). Almost all of the lymphoblastic cells expressing c-kit protein responded to recombinant human (rh)SCF with a downregulation of c-kit receptors. A proliferative response was detected only in a minority of these cells. B-ALL or BL cell lines showed no response to rhSCF. Upregulation of c-kit in T-lymphoblastic cells could be demonstrated by the addition of IL-1 beta, TNF-alpha, TGF-beta or A23187, and downregulation by rhSCF or phorbol myristate acetate (PMA). Despite upregulation of c-kit mRNA, protein remained undetectable on B-ALL or BL cells in the presence of A23187. The metabolic state of the cells seemed to influence c-kit expression, since c-kit was upregulated in T-lymphoblastic cells by the addition of new medium. C-kit appears to play a role in the growth of some malignant T-lymphoblastic but not B-lymphoblastic cells.
...
PMID:C-kit receptors in childhood malignant lymphoblastic cells. 916 31

Expression of the c-kit proto-oncogene receptor on mast cells is essential for their normal proliferation and maturation as well as for several biological responses such as chemotaxis and attachment. In the present study we report that the interleukin-3 (IL-3)-dependent mast cell line CFTL-15 lacks the extracellular domain of the c-kit receptor. This observation was made after noting that the c-kit ligand stem cell factor (SCF) could not prevent IL-3 deprivation-induced mast cell apoptosis and that CFTL-15 cells did not proliferate in response to SCF. Flow cytometric analysis employing monoclonal anti-c-kit antibodies, and immunogold labelling with analysis by electron microscopy, subsequently showed a diminished expression of c-kit on CFTL-15 cells. There was no identifiable message for the extracellular domain of c-kit in these cells, as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). These previously unrecognized properties of the CFTL-15 mast cell line allowed the examination of other biological consequences of the lack of c-kit on mast cells. Analysing the ability of these cells to adhere to surface-bound fibronectin, it was found that addition of SCF did not increase their adhesion to this substrate, in opposition to what is reported with other mast cells. Similarly, CFTL-15 mast cells did not adhere to fibroblasts, which is known to require c-kit expression. Also, there was no protein tyrosine phosphorylation in these cells in response to SCF. CFTL-15 cells underwent apoptosis on removal of IL-3 coincident with a decrease in endogenous Bcl-2 mRNA. Overexpression of Bcl-2 cDNA prolonged survival of Bcl-2-transfected CFTL-15 cells upon withdrawal of IL-3. Thus, the CFTL-15 cell line that lacks surface c-kit is not able to proliferate in response to SCF, undergoes apoptosis in the presence of SCF, and does not adhere to fibroblasts. These results confirm earlier studies on the functional consequences of c-kit and provide a novel experimental model for further investigation.
...
PMID:Characterization of a mast cell line that lacks the extracellular domain of membrane c-kit. 917 4

The expression of c-kit and flk-2/flt3 was analyzed in various stages of mast cell differentiation using reverse transcriptase polymerase chain reaction (RT-PCR). Mouse fetal liver cells were sorted using antibodies for Sca-1 (Ly6A/E) and CD43 to obtain a population enriched for early progenitors; committed mast cell progenitors were absent from this population. Mouse fetal liver-derived, IL-3-dependent blast cell colonies provided a source of committed mast cell progenitors, and mast cell colonies provided mature mast cells. Comparison of these populations showed that some uncommitted cells express both c-kit and flk-2/flt3. At the time of commitment to the mast cell lineage, the expression of c-kit increases compared to that of uncommitted progenitors, and the expression of flk-2/flt3 becomes undetectable. Previous studies have shown that steel factor, the ligand for c-kit, supports mast cell differentiation in vivo and in vitro. In contrast, the ligand for flk-2/flt3 is inactive on mast cells. Thus, receptor gene expression appears to be an important determinant of the response or lack of response of mast cells to the ligands for these two homologous receptors.
...
PMID:Loss of flk-2/flt3 expression during commitment of multipotent mouse hematopoietic progenitor cells to the mast cell lineage. 921 38

Here we review our recent data addressing the role of recombinant human (rh) interleukin 9 (IL-9) in acute myeloblastic leukemia (AML). We first evaluated the proliferative response of 3 leukemic cell lines and 32 primary samples from AML patients to IL-9 alone and combined with rh-IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF, c-kit ligand). The colony forming ability of leukemic cells was assessed by a clonogenic assay in methylcellulose, whereas the cell cycle characteristics of the same samples were determined by the acridine-orange (AO) flow cytometric technique and the bromodeoxyuridine (BRDU) incorporation assay. In addition, the terminal deoxynucleotidyl transferase Assay (TDTA) and standard analysis of DNA cleavage by gel electrophoresis were used to evaluate induction or prevention of apoptosis by IL-9. IL-9, used as a single cytokine, at various concentrations stimulated the colony formation of the 3 myeloid cell lines under serum-containing and serum-free conditions and this effect was completely abrogated by anti-IL-9 monoclonal antibodies (MoAbs). When tested on fresh AML samples, optimal concentrations of IL-9 resulted in the increase of the blast colony formation in all the cases studied and was the most effective CSF for promoting leukemic cell growth among those tested in this study including SCF, IL-3, and GM-CSF. The addition of SCF to IL-9 demonstrated an additive or synergistic effect of the 2 cytokines in 5 out of 8 AML cases tested for their CFU-L growth (187 +/- 79 colonies in comparison with 107 +/- 32 CFU-L; p = 0.05). Positive interaction was also observed when IL-9 was combined with IL-3 and GM-CSF. Studies of cell cycle distribution of AML samples demonstrated that IL-9 alone significantly augmented the number of leukemic cells in S-phase in the majority of the cases evaluated. IL-9 and SCF in combination resulted in a remarkable decrease of the G0 cell fraction (38.2 +/- 24% compared to 58.6 +/- 22% of control cultures; p < 0.05) and induced an increase of G1 and S-phase cells. Conversely, neither IL-9 alone nor the combination of IL-9 and SCF had any effect on induction or prevention of apoptosis of leukemic cells. Furthermore, in this study, reverse transcriptase-polymerase chain reaction amplification (RT-PCR) did not show the constitutive expression of IL-9 mRNA in the cell lines and the AML samples studied at diagnosis. In summary, IL-9 may play a role in the development of acute myeloid leukemia by stimulating the proliferation of leukemic cells perhaps through a paracrine growth loop.
...
PMID:Interleukin-9 in human myeloid leukemia cells. 938 63

We examined 13 human gastric carcinoma cell lines for the expression of both c-kit and stem cell factor (SCF). Expression of mRNAs was detected by both Northern blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR), and expression of translated proteins was detected by western blotting. Using RT-PCR we confirmed the expression of c-kit in five (ECC12, TMK1, MKN7, GCIY, and HGC27) cell lines. Northern blot analysis showed coexpression of both c-kit and SCF in ECC12 and expression of SCF in five other (MKN74, MKN1 OKAJIMA, KATOIII, and TMK1) cell lines. SCF stimulated both tyrosine phosphorylation of c-kit and growth of ECC12, whereas it did not stimulate those of GCIY. The sizes of c-kit transcript and protein in GCIY were slightly smaller than those of the reported ones, suggesting the presence of a biologically inactive truncated form of c-kit in GCIY. The present study suggests that c-kit/SCF system might play an important role in the carcinogenesis and tumor growth of ECC12 and that the truncated form of c-kit in GCIY might not be associated with malignant transformation.
...
PMID:Expression of protooncogene c-kit and its ligand stem cell factor (SCF) in gastric carcinoma cell lines. 950 39

During development, mice with mutations of stem cell factor (SCF) or its receptor c-kit exhibit defects in melanogenesis, as well as hematopoiesis and gonadogenesis. Consequently, accumulating evidence suggests that the c-kit/SCF system plays a crucial role in all of these processes and in tumors which derive from them. Especially in neuroblastoma (infant tumors of neuroectoderm crest derivation such as melanocytes) it would appear that an autocrine loop exists between c-kit and SCF, and that the functional block of the c-kit receptors with monoclonal antibodies (MoAbs) results in a significant decrease in cellular proliferation. We studied the expression and role of c-kit and SCF in cell lines of soft tissue sarcoma of neuroectodermic origin, such as Ewing's sarcoma (ES) and peripheral neuro-ectodermal tumors (PNET). Using flow cytometry with MoAb CD117 PE, c-kit expression was highlighted in all six of the cell lines examined. This receptor was specifically and functionally activated by SCF, as shown by the binding experiments and the intracellular phosphotyrosine and immunoprecipitation studies that were performed. Using reverse transcriptase polymerase chain reaction analysis, five of the six cellular lines expressed the mRNA of SCF. In the medium measured by using an enzyme- linked immunosorbent assay, low concentrations of SCF were found: only the TC32 cellular line produced significantly higher levels (32 pg) than control. In serum-free culture the addition of SCF reduced the percentage of apoptotic cells from 25% to 90% in five out of the six cellular lines. This observation was confirmed by (1) the functional block of c-kit with MoAb: after 7 days of culture more than 30% of the cells were apoptotic (range 31.5% to 100%) in five out of six cell lines and there was also a decrease in the percentage of cells in phase S, and (2) c-kit antisense oligonucleotides: in the cellular lines treated with oligonucleotides (in relation to the untreated lines) there was a notable reduction (P < .001) both in the absolute number of cells and the 3H-thymidine uptake. These results indicate that ES and PNET express c-kit and its ligand SCF and that SCF is capable of protecting the tumor cells against apoptosis. Furthermore, the reverse transcriptase-polymerase chain reaction performed on the biopsies revealed the presence of mRNA both of SCF and c-kit in practically all of the samples studied. Our in vitro data lead us to assume that SCF may also inhibit tumor cell apoptosis in vivo.
...
PMID:c-kit is expressed in soft tissue sarcoma of neuroectodermic origin and its ligand prevents apoptosis of neoplastic cells. 951 39

We describe the case of a 69-year-old man with systemic mastocytosis and severe osteopetrosis who carries a somatic activating mutation in the c-kit proto-oncogene. The patient initially presented with urticaria pigmentosa, progressing to systemic mast cell disease with severe anemia due to bone marrow involvement, chronic diarrhea, and hepatosplenomegaly. Direct sequencing using amplimers from reverse transcriptase-polymerase chain reactions (RT-PCR) from skin mast cell-derived RNA revealed a point mutation in the c-kit proto-oncogene at position 2468, introducing a new recognition site for the restriction endonuclease HinfI. Treatment with interferon-alpha 2a, prednisone, and erythropoietin was initiated. Subsequently, clinical symptoms improved significantly and hemoglobin levels are now stable at 13 g/dl.
...
PMID:c-kit mutation and osteopetrosis-like osteopathy in a patient with systemic mast cell disease. 979 83

The mammary tumor is one of the popular neoplastic diseases in female dogs. In the present study, the expression of canine c-kit proto-oncogene in mammary tumor specimens was investigated to evaluate its potential usefulness as a tumor marker. By comparing the homology among the nucleotide sequences reported for human mouse, rat and feline c-kit c-DNA, a pair of primers was synthesized for the reverse transcriptase-polymerase chain reaction (RT-PCR) method. The RT-PCR product of canine spleen total RNA was shown to have 756 bp in size and to be highly homologous to the corresponding sequences reported for the mammalian species. The expression of c-kit transcript was detected in 11 mammary tumors of different histopathology including adenocarcinomas, benign and malignant mixed tumors. The level of the transcription in adenocarcinomas was significantly higher than those in malignant mixed tumors. Fifteen canine tumor specimens originated from various tissues were also tested for their c-kit transcript. In all of the mastocytoma samples examined, high expression of the mRNA was detected. Of other 12 tumors, only low level of RT-PCR products were detected in 5 samples, whereas no apparent amplification was observed in 7 tumors. These results indicate that the high expression of c-kit transcript is helpful for the diagnosis of canine mammary tumors.
...
PMID:Frequent expression of the c-kit proto-oncogene in canine malignant mammary tumor. 987 35

The expression pattern of c-fos, c-jun, c-kit and stem cell factor (SCF) has been investigated in developing human placenta using the highly sensitive technique of in situ reverse transcriptase-polymerase chain reaction (RT-PCR). Specific transcripts of all genes under study were observed in first-trimester placenta sections. c-fos, c-jun, c-kit and SCF transcripts were localized in cells of the villous stroma; fos, jun and kit-specific mRNAs were also found in endothelial cells; fos, kit and SCF mRNAs were detected in villous trophoblast cells. In mid-trimester and term placenta specimens only SCF transcripts were observed, restricted to trophoblast cells. The lack of c-fos transcripts in placenta from the second and third trimesters is a finding that contrasts with data from the literature obtained using extractive techniques. Parallel immunocytochemistry of placenta specimens from the three pregnancy stages under study revealed the fos protein only in first-trimester placenta, in agreement with the in situ RT-PCR findings. We conclude that the in situ RT-PCR technique is most suitable for gene expression studies because of its high level of sensitivity in correctly assigning the signal to specific cell types in complex tissues.
...
PMID:Localization of fos, jun, kit and SCF mRNA in human placenta throughout gestation using in situ RT-PCR. 1008 77

The purpose of this study was to isolate pure populations of round spermatids from mouse testis by flow cytometry followed by cell sorting. Cell suspensions from mouse testis were enriched in germ cells by centrifugation on a discontinuous Percoll gradient, then analysed using a FACScalibur flow cytometer measuring the cell size and density. A large and well-delimited population of cells (R1) expected to contain round spermatids was observed on the dot plot diagram. Sorted R1 cells were very homogeneous in size (approximately 11 microns) and displayed the characteristic cytological aspect of round spermatids. Spermatid-specific gene expression was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of R1 cells using primers for protamine 2 gene (PRM2) and SP-10. A positive signal for SP-10 was obtained with a single cell using nested primers. The 5.5 kb transcript of c-kit, which is not expressed in spermatids, was not detected by nested RT-PCR, excluding a contamination with spermatogonia. Our results clearly established that flow cytometry followed by cell sorting allows the isolation of a highly homogeneous population of round spermatids from the testis.
...
PMID:Flow cytometric method to isolate round spermatids from mouse testis. 1009 85


<< Previous 1 2 3 4 5 6 Next >>

---