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)

Myelodysplastic syndromes originate from a pluripotent stem cell. This view, previously suggested by G-6-PD and cytogenetic investigations, has been established unequivocally by X-chromosome inactivation analysis based on DNA polymorphisms and by studies of mutated oncogenes. Two genomic alterations associated with MDS have been analyzed in more detail. Activation of the RAS oncogenes, preferentially N-RAS, is demonstrated in approximately 35% of MDS patients. Mutations in the FMS gene, encoding the CSF-1 receptor, are found in 16% of cases. Interestingly, RAS and FMS mutations are predominantly observed in disorders of myelomonoctic differentiation, i.e., the CMML subtype in MDS and the AML FAB type M4. Moreover, homozygous deletion of the FMS gene may be an important event in the genesis of the MDS variant 5q- syndrome. Preliminary data indicate that defects in tumor-suppressor genes, namely p53, may also contribute to the development of MDS. Different lines of evidence suggest that clinical preleukemia is preceded by a phase in which genetic alterations accumulate without any hematologic change. Cases in point are the detection of RAS and FMS mutations in healthy individuals who had been treated in the past with cytotoxic therapy for lymphoma, the frequent observation of clonal remission in AML patients, or the identification of oncogene mutations in healthy individuals without even a history of malignancy or chemotherapy. Possibly, either germline mutations of oncogenes or tumor-suppressor genes and the process of genomic imprinting may constitute additional factors that predispose hematopoietic stem cells to malignant transformation. Limited as they are, the currently available data suggest that accumulation of genomic lesions, rather than their precise order of development with respect to one another, characterize the multistep process of leukemogenesis in which MDS already represent more advanced stages. The prognostic significance of oncogene mutations in MDS patients is controversially discussed. This issue awaits prospective analyses taking into account the influence of treatment modalities. However, the clinical relevance of molecularly defined parameters has already been established for their use as clonal markers in determining the mode of action and efficiency of different therapeutic approaches.
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PMID:Molecular genetic aspects of myelodysplastic syndromes. 161 6

Karyotypic abnormalities in primary myelodysplastic syndrome (P-MDS) are less frequent than in secondary myelodysplasia. A review of the literature involving over 3000 reported cases, shows the incidence of karyotypically abnormal clones at presentation in nearly 48% of cases. Approximately 50% of the abnormalities comprise of deletions of chromosomes 5, 7, 11, 12, 13 and 20. Localisation of a number of haemopoietic growth factors and their receptors to the deleted segments of the chromosomes, has invoked considerable interest in the molecular pathology of the interstitial deletions and their consequent role in the multistep pathogenesis of MDS. Present evidence suggests chromosome abnormalities are a later event in the multistep painogenesis, and it is suggested their occurrence may be restricted to a restricted myeloid progenitor cell, although the initial event(s) occur at the common lymphoid-myeloid progenitor. Much has been gleaned from the dominant modes of leukaemogenesis, such as the occurrence of missense mutations at specific positions of RAS and FMS mutations. It is suggested that a similar enquiry into the mechanisms of chromosomal deletions in P-MDS is required in order to delineate the role of these abnormalities in the clonal evolution of this group of diseases.
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PMID:Chromosomal deletions in the myelodysplastic syndrome. 173 67

Abnormalities of chromosome 7 are among the most frequent cytogenetic aberrations found in MDS, including de novo cases and cases secondary to chemo- and/or radiotherapy. Since MET is located on 7q and as Cooper et al (1984) showed that MET proto-oncogene could be activated by a chemical carcinogen, we tried to evaluate whether it could be implicated in some cases of MDS. With specific probes for MET we analysed the DNA of 88 MDS patients (81 de novo and seven secondary cases). In 17 of them the RNA was also studied. We found no rearrangement or aberrant expression of MET in any samples studied. Our results, however, do not rule out point mutations or rearrangement of other regions of MET or adjacent DNA regions.
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PMID:Absence of rearrangement of proto-oncogene MET in 88 cases of myelodysplastic syndromes (MDS). 280 76

Most studies of the clonal origin of the underlying lesion(s) and all investigations using X-inactivation, have concluded that the myelodysplastic syndromes arise from a multipotent stem cell. Non-random chromosomal abnormalities, particularly deletions of 5q and 7q, are common, most notably in therapy related MDS. Progression to AML is also frequently accompanied by increased genomic instability as evidenced by the emergence of multiple karyotypic abnormalities. While some evidence hints at the presence of tumour suppressor genes on chromosomes 5, 7, 20 and 12, no such genes have yet been identified. The search for point mutations in known oncogenes has concentrated on two oncogenes RAS and c-FMS. Point mutation frequency generating active forms of RAS oncogenes is approximately 40% in MDS overall, up to 80% in studies of CMML. 60% of all MDS RAS mutation involves a G to A transition, producing a substitution of aspartate for glycine at a frequency of 50% (of total ras mutants). RAS mutation is associated with progression to AML, although the presence of a RAS point mutation alone is neither necessary nor sufficient for leukaemic transformation. Mutation of c-FMS is also more common in CMML in comparison to other MDS subtypes and, as yet, point mutation potentiating the response of the receptor to CSF-1 (codon 969) has been found more frequently than point mutation resulting in permanently activated receptor (codon 301). However, recent work has identified additional mutations which produce transforming proteins, and mutation rates at these sites may be relevant in MDS.
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PMID:Myelodysplastic syndromes: from morphology to molecular biology. Part II. The molecular genetics of myelodysplasia. 849 99

It has been supposed in de novo AML that malignant transformation occurs at the level of committed progenitors. Recent data of our group and others provide evidence that in AML malignant transformation may regularly occur at the level of stem cells. These cells can be discriminated by function and specific surface molecules. CD34, a glycophosphoprotein, is a cellular surface antigen characteristically expressed by stem cells. CD34+ stem cells can be further subdivided by the expression of additional surface molecules like CD38 and CD117. In this article we present results from cytogenetic examinations of FACS-isolated stem cell subpopulations in eight patients (four AML and four MDS). Six of them displayed clonal karyotype abnormalities at the time of first diagnoses in the native bone marrow (5q-; 5q- and complex abnormalities; +8; inv(16) and +8; i(17q) and -21; i(21q)). We used CD117, the receptor for the stem cell factor (also KIT oncogene) as a new cellular surface marker. CD34+/CD117+/- stem cell subpopulations were examined in two patients with AML and three patients with MDS. We found leukemic stem cells in every type of stem cell subpopulation examined (CD34+/CD38-, CD34+/CD38+, CD34+/CD117-, CD34+/CD117+). Secondary, progression-associated chromosome abnormalities likewise were demonstrable in CD34+ cells. In three patients a mosaic of normal and abnormal metaphases was found in the highly purified stem cell subpopulations. We conclude that in AML and MDS stem cells are the target of leukemogenic genetic defects. CD117 as a new marker to isolate different CD34+ subpopulations was not sufficient to discriminate between normal and leukemic stem cells. Our findings have implications for autologous stem cell transplantation, high-dose chemotherapy and the pathogenetic concept of leukemogenesis.
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PMID:Cytogenetic analysis of CD34+ subpopulations in AML and MDS characterized by the expression of CD38 and CD117. 918 Feb 91

The NPM-MLF1 fusion protein is expressed in blasts from patients with myelodysplasia/acute myeloid leukemia (MDS/AML) containing the t(3;5) chromosomal rearrangement. Nucleophosmin (NPM), a previously characterized nucleolar phosphoprotein, contributes to two other fusion proteins found in lympho-hematopoietic malignancies, anaplastic large cell lymphoma (NPM-ALK) and acute promyelocytic leukemia (NPM-RARalpha). By contrast, the function of the carboxy-terminal fusion partner, myelodysplasia/myeloid leukemia factor 1 (MLF1), is unknown. To aid in understanding normal MLF1 function, we isolated the murine cDNA, determined the chromosomal localization of Mlf1, and defined its tissue expression by in situ hybridization. Mlf1 was highly similar to its human homologue (86% and 84% identical nucleotide and amino acid sequence, respectively) and mapped to the central region of chromosome 3, within a segment lacking known mouse mutations. Mlf1 tissue distribution was restricted during both development and postnatal life, with high levels present only in skeletal, cardiac, and selected smooth muscle, gonadal tissues, and rare epithelial tissues including the nasal mucosa and the ependyma/choroid plexus in the brain. Mlf1 transcripts were undetectable in the lympho-hematopoietic organs of both the embryonic and adult mouse, suggesting that NPM-MLF1 contributes to the genesis of MDS/AML in part by enforcing the ectopic overexpression of MLF1 within hematopoietic tissues.
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PMID:cDNA cloning, expression pattern, and chromosomal localization of Mlf1, murine homologue of a gene involved in myelodysplasia and acute myeloid leukemia. 1039 36

The t(11;20)(p15;q11) is a rare but recurrent translocation that so far has been described in only four acute myeloid leukemias (AMLs), two treatment-related myelodysplastic syndromes (t-MDSs), and one case of polycythemia vera. Recently, the t(11;20) was shown to result in a fusion of the NUP98 and TOP1 genes, with expression of the NUP98/TOP1 chimera encoded by the der(11)t(11;20), but not of the reciprocal TOP1/NUP98 on the der(20)t(11;20). The genomic breakpoints were subsequently mapped to introns 13 and 7 of NUP98 and TOP1, respectively. We present here a t-MDS with a three-way variant translocation, t(10;20;11)(q24;q11;p15), that generates a der(11)t(11;20) but not a der(20)t(11;20), strongly suggesting that the der(11) harbors the critical genetic rearrangement. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed a NUP98/TOP1 fusion in which exon 13 of NUP98 was fused in-frame with exon 8 of TOP1. Extra long (XL) genomic PCR and subsequent sequence analyses showed that the breakpoint in NUP98 occurred at nucleotide (nt) 3461 of intron 13, close to a MER (medium reiteration frequency interspersed repetitive element) repeat, and that the breakpoint in TOP1 was at nt 1436 of intron 7, downstream of a MIR (mammalian-wide interspersed repeats) repetitive element. Genomic XL PCR did not amplify the reciprocal TOP1/NUP98, nor was this chimera expressed, as expected from the cytogenetic finding. The present results provide further support for the involvement of the NUP98/TOP1 transcript, but not of the reciprocal one, in the development of MDS/AML. Furthermore, the three cases genomically characterized to date have all been treatment-related and have all harbored breakpoints in intron 13 of NUP98 and intron 7 of TOP1, suggesting that these introns are susceptible to chemotherapy-induced breakage.
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PMID:Expression of NUP98/TOP1, but not of TOP1/NUP98, in a treatment-related myelodysplastic syndrome with t(10;20;11)(q24;q11;p15). 1197 59

Because a previous study by conventional cytogenetics had revealed a nullisomy 17 in the breast cancer cell line EFM-19, we analysed that cell line by SKY-FISH and by FISH using different probes derived from chromosome 17. A bicolor FISH using a HER2-specific probe and a chromosome 17 centromeric probe showed five HER2 and six centromeric signals all appearing on different chromosomes A further bicolor FISH using a chromosome 17-specific painting probe and a HER2-specific probe revealed that the HER2 signals were always localized within chromosome 17 segments constituting part of structurally altered chromosomes as deduced from their G-banding. Further FISH analyses using single-locus probes of chromosome 17, i.e., for MDS, p53, SMS and RARA, showed that all five chromosome 17 painting segments contained material from the long arm but only two painting segments had additional material from the short arm. A SKY-FISH confirmed the results of the chromosome 17 painting by FISH, except for one structurally altered chromosome showing additional chromosome 17 material detected by the SKY experiment. These results allow us to conclude that, in this cell line, polysomy 17 has preceeded the fragmentation of chromosome 17 leading to amplification of small parts of that chromosome as well as to extended losses. As to a general mechanism, polysomy 17 and a fragility of this, chromosome in breast cancer cells may not only account for part of the cases with HER2 amplification but, at the same time, may further support malignant progression due to the loss of tumor suppressor genes as e.g. p53.
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PMID:Molecular-cytogenetic analysis of fragmentation of chromosome 17 in the breast cancer cell line EFM-19. 1217 75

Somatic mutation of the FLT3 gene as an internal tandem duplication (ITD) of the juxtamembrane domain-coding sequence causes constitutive tyrosine phosphorylation and activation. Tumor-specific DNA has been documented in the sera of patients with solid tumors even when it is in an early stage. We compared the detection of FLT3 ITD in DNA extracted from cells of bone marrow (BM) aspirations with DNA extracted from peripheral blood (PB) plasma in patients newly diagnosed with acute myeloid leukemia (AML; 85 patients), myelodysplastic syndrome (MDS; 16 patients), and acute lymphocytic leukemia (ALL; 16 patients). FLT3 ITD was detected in 18 (21%) AML samples and in one (6%) MDS sample in both cellular and plasma DNA but in none of the ALL samples. Hemizygous/homozygous FLT3 ITD was detected in five (28%) of the FLT3 ITD-positive AML using plasma DNA, whereas only four of these cases showed hemizygous/homozygous FLT3 ITD using cellular DNA. The presence of FLT3 ITD was associated with significantly shorter survival (P = 0.02) when only patients younger than 50 years of age (48 AML+MDS patients) were considered. This finding was independent of cytogenetics in this age group. However, patients with the FLT3 ITD hemizygous/homozygous phenotype had even shorter survival (P = <0.001). As expected, the presence of FLT3 ITD correlated with higher white blood cell (WBC) counts. These data demonstrate that plasma DNA is a reliable alternative resource for detecting FLT3ITD, especially the hemizygous/homozygous genotype. Furthermore, the data derived from this study support the notion that the presence of FLT3 ITD in conjunction with the absence of the wild-type FLT3 allele predicts an especially poor prognosis for patients with AML.
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PMID:Better detection of FLT3 internal tandem duplication using peripheral blood plasma DNA. 1252 67

Both ITD and D835 mutations of the fms-like tyrosine kinase (FLT3) gene cause constitutive activation of the receptor, in the absence of ligand. We have examined a cohort of 91 patients, AML (80) and MDS (11), to determine the prevalence of these mutations and any correlations between the two mutations and disease prognosis. FLT3/ITD (ITD+) or D835 mutations (D835+) were not detected in MDS patients examined. However, 10% (8/80) and 7.5% (6/80) of AML patients were ITD+ and D835+, respectively. ITD+ patients have a higher rate of relapse than patients with wild-type (WT) FLT3. Median overall survival was 4.6 months (range 0.6-36.2) for ITD+ and 19.85 months (range 0.2-197.5) for WT patients (P=0.0066), and disease-free survival (DFS) was also worse for ITD+ patients than FLT3/WT patients (P=0.047). FLT3/ITD is also a significant prognostic marker for overall survival (OS) and DFS in patients in the standard karyotype group (P=0.0040, 0.0365, respectively). ITD is more prevalent in patients in the standard karyotype category (7/41, 17.1%) as compared to patients in the poor-risk category (1/32, 3.1%). Similar to ITD, D835 mutations were found to be more frequent in patients with standard-risk rather than poor-risk cytogenetic category. WBC count (mean 63.8 x 10(9)/l) was significantly higher in ITD+ patients than patients with D835 mutations (mean 34.8 x 10(9)/l) and WT patients (mean 26.4 x 10(9)/l) (P=0.004). D835 mutants did not appear to have a worse median OS or DFS compared with the WT group. We conclude that FLT3/ITD mutations may be an important prognostic marker in AML, especially in the standard/good risk karyotype groups, where it may allow risk-directed therapy.
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PMID:Prognostic significance of FLT3 ITD and D835 mutations in AML patients. 1269 19


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