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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies over the last 40 years have led to an understanding of the hierarchical organization of the hematopoietic system and the role of the pluripotential hematopoietic stem cell. Earlier recognition of the importance of bone marrow hematopoietic microenvironments has evolved into the recognition of specific niches that regulate stem cell pool size, proliferative status, mobilization, and differentiation. The discovery of the role of multiple hematopoietic growth factors and their receptors in the orchestration of stem cell self-renewal and differentiation has been followed by recognition of the importance of the Notch and Wnt pathways. The homeobox family of transcription factors serve as master regulators of development and are increasingly found to be critical regulators of hematopoiesis. In parallel with this understanding of normal hematopoiesis has come a recognition that stem cell dysregulation at various levels is involved in leukemogenesis. Furthermore, the progression from chronic leukemia or myelodysplasia to acute leukemia involves accumulation of at least two mutational events that lead to enhancement of stem cell proliferation, or acquisition of stem cell behavior by a progenitor cell, coupled with maturation inhibition. Translocations resulting in development of oncogenic fusion genes are found in AML and the transforming potential of two of these, AML1-ETO and NUP98-HOXA9, will be discussed. Secondary, constitutively activating mutations of the Flt3 and c-kit receptors and of K- and N-ras are found with high frequency in AML, and the transforming potential of mutated FLT3 and the role of STAT5A activation in human stem cell transformation will be reviewed.
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PMID:Converging pathways in leukemogenesis and stem cell self-renewal. 1596 48

Over the last decade, major advances have been made in the elucidation of mechanisms involved in leukemogenesis, and this is particularly true with regard to deregulated protein tyrosine kinase (PTK) activation. This progress had led to the development of small molecules that specifically inhibit the abnormally activated kinase. The first example of such targeted therapy is imatinib-mesylate, an inhibitor of the BCR-ABL fusion gene that is found in more than 90% of patients with Philadelphia positive (Ph+) chronic myeloid leukemia (CML) and in 20-30% of those with Ph+ acute lymphoblastic leukemia (ALL). The excellent clinical results obtained with imatinib in CML have completely changed the therapeutic approach to this disease, and imatinib is now the gold standard for treatment of newly diagnosed CML. This has instigated a tremendous effort to develop targeted PTK therapy based on the presence of over 40 chromosomal translocations that lead to deregulation of 12 different PTK associated with various hematologic malignancies. That deregulated PTK are also involved in the pathogenesis of acute leukemia is underlined by the frequent occurrence of mutations leading to constitutive activation of the FLT3. Experimental as well as clinical evidence supports a model of acute leukemia based on the co-operation of constitutive active PTK with mutations of transcriptional regulators. Here we review the general impact of mutated PTK on the pathogenesis of various hematologic malignancies. We also discuss the development of new targeted therapies and strategies to circumvent the increasing problems related to the emergence of drug resistance by targeting downstream signaling mediators that are essential for transformation by deregulated PTK.
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PMID:Targeting mutated protein tyrosine kinases and their signaling pathways in hematologic malignancies. 1599 23

The molecular characterization of leukemia has demonstrated that genetic alterations in the leukemic clone frequently fall into 2 classes, those affecting transcription factors (e.g., AML1-ETO) and mutations affecting genes involved in signal transduction (e.g., activating mutations of FLT3 and KIT). This finding has favored a model of leukemogenesis in which the collaboration of these 2 classes of genetic alterations is necessary for the malignant transformation of hematopoietic progenitor cells. The model is supported by experimental data indicating that AML1-ETO and FLT3 length mutation (FLT3-LM), 2 of the most frequent genetic alterations in AML, are both insufficient on their own to cause leukemia in animal models. Here we report that AML1-ETO collaborates with FLT3-LM in inducing acute leukemia in a murine BM transplantation model. Moreover, in a series of 135 patients with AML1-ETO-positive AML, the most frequently identified class of additional mutations affected genes involved in signal transduction pathways including FLT3-LM or mutations of KIT and NRAS. These data support the concept of oncogenic cooperation between AML1-ETO and a class of activating mutations, recurrently found in patients with t(8;21), and provide a rationale for therapies targeting signal transduction pathways in AML1-ETO-positive leukemias.
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PMID:The AML1-ETO fusion gene and the FLT3 length mutation collaborate in inducing acute leukemia in mice. 1602 55

We reported previously that KG-1, a human acute leukemia cell line, has mutational loss of 8-oxoguanine (8-hydroxyguanine; oh8Gua) glycosylase 1 (OGG1) activity and undergoes apoptotic death after treatment with 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodeoxyguanosine, 8-hydroxydeoxyguanosine; oh8dG). In our present study, we further characterized the effects of oh8dG in KG-1 cells and found that, in addition to apoptosis, oh8dG induced the arrest of KG-1 at the G1 phase. Simultaneously, oh8dG-treated KG-1 showed an increase in the oh8Gua content of DNA, upregulation of p21 (an inhibitor of cdk), and Ras inactivation. Moreover, the upregulation of p21 was followed by the inactivations of cdk4 and cdk2, the hypophosphorylation of Rb, and a marked decline in the expression of c-myc (a gene regulated by E2F that is a transcription factor whose activity is suppressed when it is bound to hypophosphorylated Rb). Ras inactivation was also followed by the inactivation of ERK kinase (MEK) and the inactivation of AP-1, a downstream target of the Ras signaling pathway. The specific MEK inhibitors, PD98059 and U0126, also induced G1 arrest. These findings suggest that p21 upregulation and Ras inactivation contribute to G1 arrest. An increase of oh8Gua content in DNA does not seem to be a principal contributor to G1 arrest, however, because the kinetics of increases of oh8Gua content in DNA and of G1 cell number did not coincide. We report that oh8dG induces the arrest of KG-1 growth at the G1 phase mainly by upregulating p21 and inactivating Ras.
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PMID:Oh8dG induces G1 arrest in a human acute leukemia cell line by upregulating P21 and blocking the RAS to ERK signaling pathway. 1605 17

The receptor tyrosine kinase FLT3 is an important regulatory molecule in hematopoiesis and is expressed on the blasts in most cases of acute leukemia. Activating mutations of this receptor are present in roughly 30% of acute myeloid leukemia (AML) patients and are associated with a distinctly worse clinical outcome. Efforts to target this mutation and improve out-comes in this subgroup of AML patients have led to the investigation of several novel small-molecule FLT3 tyrosine kinase inhibitors. These compounds derive from a wide variety of chemical classes and differ significantly, both in their potency and in their selectivity. In this review, we discuss the results of preclinical, clinical, and correlative laboratory studies of FLT3 inhibitors in demonstrating how this field represents a truly translational enterprise with multiple ongoing interactions between the laboratory and the clinic.
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PMID:FLT3 tyrosine kinase inhibitors. 1614 39

A rare case of a 46-year-old man who underwent myelodysplastic syndrome, acute monocytic leukemia with FLT3-ITD mutation and splenic disruption following orthotopic liver transplantation is reported. The study of this case may be helpful to understand both the pathogenesis of acute leukemia and new complication of liver transplantation.
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PMID:Myelodysplastic syndrome with transformation to acute monocytic leukemia with FLT3-ITD mutation following orthotopic liver transplantation. 1641 20

The progenitor cells of myelodysplastic syndrome (MDS) are thought to undergo a multistep process during their transformation into overt acute leukemia. In this study, the role of mutation of the KIT gene in the extracellular membrane, juxtamembrane and tyrosine kinase domains was investigated in 75 patients with MDS or MDS-derived leukemia (MDS-AML). Mutation was detected in 2 of 15 (13.3%) patients with refractory anemia with excess blasts transformation (RAEB-T), in 1 of 15 (6.6%) patients with chronic myelomonocytic leukemia (CMML), and in 5 of 26 (19.2%) patients with MDS-AML. However, no mutation was found in any of the nine patients with refractory anemia (RA) or the 10 patients with refractory anemia with excess blasts (RAEB). Of the mutations, five patients had changes at the same codon in tyrosine kinase domain, Asp816, while the remainder had unique mutations. These observations suggest that KIT gene mutations identified in the advanced stage of MDS, and genetic abnormality in the KIT gene, particularly at codon 816, might be additional events that contribute to the progression of MDS to AML.
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PMID:Mutational analysis of the KIT gene in myelodysplastic syndrome (MDS) and MDS-derived leukemia. 1653 29

Currently, Arsenic Trioxide (ATO) is considered the treatment of choice for patients with relapsed acute promyelocytic leukemia (APL). Recently, a durable remission with minimal toxicity by single agent ATO or ATO + ATRA in newly diagnosed APL was reported by different groups. These regimens have minimal toxicity and can be administered on an outpatient basis after remission induction, thus they could become a real, less toxic and more economic option to ATRA + anthracyclines in particular in low risk APL, or in patients that cannot undergo chemotherapy because of age or comorbid conditions and in patients that refuse chemotherapy. Significantly, these therapies are a successful attempt to cure a tumoral disease without chemotherapy. The results of clinical trials of ATO administration as single agent in multiple myeloma (MM) and myelodisplastic syndromes (MDS) were encouraging and showed clinical effects but they were not close to APL success. On the contrary, results of clinical trials to treat non-APL acute myeloid leukemia (AML) were disappointing. We suggest that a combination therapy with drugs targeting specific pro-survival molecules or capable to enhance pro-apoptotic pathways may lead to an improvement of ATO efficacy against hematological malignancies, in particular AML. Our pre-clinical studies showed that ATO is capable to induce cell death in acute leukemia cells but the apoptotic function is limited since it can induce also a mechanism of cell defense by activating pro-survival molecules such as MEK-ERK, Bcl-xL, Bcl-2. By combining ATO with specific MEK inhibitors, we demonstrated that the block of MEK-ERK phosphorylation, the induction of Bad de-phosphorylation, and activation of p53AIP1 apoptotic pathway interrupt the pro-survival mechanisms of ATO and kill the leukemic cells by apoptotic synergism. Our results provide an experimental basis for combined or sequential treatment with MEK inhibitors and ATO in AML. The renaissance of ATO as a drug in moderne medicine may be considered, together with ATRA success, a victory of empirical analysis, that had (and has) great impact on Chinese culture.
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PMID:Arsenic trioxide in hematological malignancies: the new discovery of an ancient drug. 1716 55

To assess the prognostic relevance of activating mutations of FLT3 gene on outcome of allogeneic transplantations in AML patients, we performed an analysis of all patients with FLT3 mutations registered in the Czech Acute Leukemia Clinical Register (ALERT) from 2003 till the end of 2005. Within the mentioned period 170 patients with AML of median age 56 years (23-77) were investigated for FLT3 mutation, within them 36 cases (21%) with FLT3 mutations (32 FLT3 ITD and 4 FLT3 D835) were found. Out of FLT3 ITD positive patients 13 had allogeneic transplantation, 20 patients with mutations of FLT3 were treated with chemotherapy without transplantation. Results of the treatment of these patients were compared with the results of the group of patients without FLT3 mutation, which was according to other characteristics identical with the group of patients with FLT3 mutations (n=134). Median overall survival (OS) was significantly shorter for patients with FLT3 ITD (34.8 weeks) than for those without FLT3 mutations (67.7 weeks; P=0.028). Median OS of patients with FLT3 ITD who had allogeneic transplantation was 42.5 weeks; median OS of patients with FLT3 ITD treated only with chemotherapy was 29.6 weeks (P=0.362). After allogeneic transplantation, median OS of FLT3 mutations negative patients was similar to FLT3 ITD positive patients (46.7 versus 42.5 weeks; P=0.443). Our results suggest that at present there is no strong evidence that FLT3 status alone should influence the decision to proceed to allogeneic transplantation in AML patients. Decision to proceed to alogeneic transplantation should not be based on the FLT3 status only, but it should also consider other prognostic factors.
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PMID:Is FLT3 internal tandem duplication significant indicator for allogeneic transplantation in acute myeloid leukemia? An analysis of patients from the Czech Acute Leukemia Clinical Register (ALERT). 1723 51

Multiplex reverse transcription-polymerase chain reaction (M-RT-PCR) has been proved to possess great clinical potential for simultaneous screening of 29 chromosomal translocations in acute leukemia. To evaluate the clinical value of M-RT-PCR in hematologic malignancies, bone marrow samples from 90 patients with various hematologic malignancies, including 25 acute myelogenous leukemia (AML), 22 acute lymphoblastic leukemia (ALL), 27 chronic myelogenous leukemia (CML), 4 myeloproliferative diseases (MPD), 3 chronic lymphoblastic leukemia (CLL), 3 non-Hodgkin's lymphoma (NHL), 3 myelodysplastic syndrome (MDS), 2 multiple myeloma (MM) and 1 malignant histiocytosis (MH) were subjected to both M-RT-PCR and chromosome karyotypic analysis. Some of cases were subjected to follow-up examination of M-RT-PCR during the period of clinical complete remission (CR) for detection of minimal residual leukemia. In our hand, 12 of 29 chromosomal translocation transcripts including TEL/PDGFR, DEK/CAN, MLL/AF6, AML1/ETO, MLL/AF9, BCR/ABL, MLL/MLL, PML/RARu, TLS/ERG, E2A/HLF, EVI1 and HOXI1 were detected in 57 cases (63.3 %) of the 90 samples, which were in consistency with the results of karyotypic analysis. Furthermore, M-RT-PCR had also shown good clinical relevance when used as an approach to detect minimal residual leukemia. We concluded that M-RT-PCR could be used as an efficient and fast diagnostic tool not only in the initial diagnosis of hematologic malignancies but also in subsequent monitor of minimal residual leukemia.
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PMID:Multiplex reverse transcription-polymerase chain reaction for simultaneous screening of 29 chromosomal translocation in hematologic malignancies. 1735 82


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