Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026986 (myelodysplastic syndrome)
 14,926 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations of the NRAS and TP53 genes and internal tandem duplication (ITD) of the FLT3 gene are among the most frequently observed molecular abnormalities in the myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). We sought to determine the incidence of these abnormalities in patients with MDS and a 5q deletion. NRAS and FLT3 mutations are uncommon in MDS patients with a 5q deletion and TP53 mutation is associated with the more advanced MDS subtypes.
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PMID:NRAS, FLT3 and TP53 mutations in patients with myelodysplastic syndrome and a del(5q). 1525 41

Leukemic cells from 30% of patients with acute myeloid leukemia (AML) have an activating mutation in the FLT3 (fms-like tyrosine kinase) gene, which represents a target for drug therapy. We treated 20 patients, each with mutant FLT3 relapsed/refractory AML or high-grade myelodysplastic syndrome and not believed to be candidates for chemotherapy, with an FLT3 tyrosine kinase inhibitor, PKC412 (N-benzoylstaurosporine), at a dose of 75 mg 3 times daily by mouth. The drug was generally well tolerated, although 2 patients developed fatal pulmonary events of unclear etiology. The peripheral blast count decreased by 50% in 14 patients (70%). Seven patients (35%) experienced a greater than 2-log reduction in peripheral blast count for at least 4 weeks (median response duration, 13 weeks; range, 9-47 weeks); PKC412 reduced bone marrow blast counts by 50% in 6 patients (2 of these to < 5%). FLT3 autophosphorylation was inhibited in most of the Corresponding patients, indicating in vivo target inhibition at the dose schedule used in this study. PKC412 is an oral tyrosine kinase inhibitor with clinical activity in patients with AML whose blasts have an activating mutation of FLT3, suggesting potential use in combination with active agents, such as chemotherapy.
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PMID:Patients with acute myeloid leukemia and an activating mutation in FLT3 respond to a small-molecule FLT3 tyrosine kinase inhibitor, PKC412. 1534 97

Therapy-related myeloid leukemia (t-AML) is a distinctive clinical syndrome occurring after exposure to chemotherapy (CT) or radiotherapy (RT). We studied 306 consecutive patients referred to the University of Chicago with cytogenetic analyses. Since 1972, 141 males and 165 females with a median age of 51 years (range: 3-83 years) at primary diagnosis and 58 years (range: 6-86 years) at secondary diagnosis were analyzed. Patients had received various cytotoxic agents including alkylating agents (240 patients, 78%) and topoisomerase II inhibitors (115 patients, 39%). One hundred and twenty-one (40%) had received CT alone, 43 (14%) had received RT alone, and 139 (45%) had received both modalities. At diagnosis of t-AML, 282 (92%) had clonal abnormalities involving chromosome 5 (n=63), chromosome 7 (n=85), both chromosomes 5 and 7 (n=66), recurring balanced rearrangements (n=31), or other clonal abnormalities (n=39); 24 had a normal karyotype. Abnormalities of chromosomes 5 and/or 7 accounted for 76% of all cases with an abnormal karyotype. Seventeen patients had developed t-AML after autologous stem cell transplantation, but no unique pattern of cytogenetic abnormalities was observed. Patients presenting with acute leukemia were more likely to have a balanced rearrangement than those presenting with myelodysplasia (28% versus 4%, p<0.0001). Shorter latency was observed for patients with balanced rearrangements (median: 28 months versus 67 months; p<0.0001). Median survival after diagnosis of t-AML was 8 months; survival at 5 years was less than 10%. To gain insights into the molecular basis of this disease, we performed gene expression profiling of CD34+ hematopoietic progenitor cells from t-AML patients. We found distinct subtypes of t-AML that have characteristic gene expression patterns. Common to each of the subgroups are gene expression patterns typical of arrested differentiation in early progenitor cells. Leukemias with a -5/del(5q) have a higher expression of genes involved in cell cycle control (CCNA2, CCNE2, CDC2), checkpoints (BUB1), or growth (MYC), and loss of expression of the gene encoding interferon consensus sequence-binding protein (ICSBP). A second subgroup of t-AML is characterized by down-regulation of transcription factors involved in early hematopoiesis (TAL1, GATA1, and EKLF) and overexpression of proteins involved in signaling pathways in myeloid cells (FLT3) and cell survival (BCL2). Establishing the molecular pathways involved in t-AML may facilitate the identification of selectively expressed genes that can be exploited for the development of targeted therapies.
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PMID:Therapy-related myeloid leukaemia: a model for leukemogenesis in humans. 1593 16

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

The myelodysplastic syndromes (MDS) are receiving unusual attention recently as great strides have been made in understanding the biology. Recognition that excessive cytokine-induced apoptosis plays a significant role in the cytopenias of the majority of patients opened the doors to anti-cytokine therapy, with thalidomide being used with success in approximately 20% patients. Other therapies that have emerged include the thalidomide analog lenalidomide which is particularly beneficial for 5q- patients as well as a subset of non-5q- patients with low or intermediate-1 risk MDS. Other targeted therapies include vitamins, agents that are cytoprotective, differentiation inducers, anti-angiogenic, or immune modulatory. In addition, inhibitors of proteasome, methylation, histone deacetylation, farnesylation, receptor tyrosine kinases, topoisomerase, and matrix mettaloproteinases have yielded encouraging responses in subsets of patients. Specific therapies have also been developed for genetic abnormalities that lead to fusion genes (TEL-PDGFR-beta, or FIP1L1-PDGFR-alpha), or abnormal proteins due to mutations/functional inactivation (FLT3), dysregulated expression (EVI-1). In a short span of ten years, the field has evolved from having no effective therapy to offer the majority of MDS patients save chemotherapy, to having one FDA approved drug, several on the way to approval, and a number of novel agents producing exciting clinical results. This chapter summarizes the novel targets and targeted therapies in the rapidly evolving therapeutic landscape of MDS.
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PMID:Translational research in myelodysplastic syndromes. 1602

Therapy-related leukemia or myelodysplasia (t-leuk/MDS) is a serious problem that is increasing in frequency. We studied the clinical characteristics of 96 patients (pts) with a mean age of 48 years, and analyzed the molecular parameters that could predispose to t-leuk/MDS. Hematological malignancies were the most common primary (53%), followed by breast and ovarian cancer (30% combined). The mean latency until the development of t-AML was 45.5 months. Median survival was 10 months. Cytogenetics was abnormal in 89% of pts. FLT3 internal tandem duplications were found in six of 41 (14.6%) pts, of whom four had an abnormal karyotype. Analysis of drug metabolism and disposition genes showed a protective effect of the CYP3A4 1*B genotype against the development of t-leuk/MDS, whereas the CC genotype of MDR1 C3435T and the NAD(P)H:quinone oxidoreductase1 codon 187 polymorphism were both noncontributory. Microsatellite instability (MSI) analysis using fluoresceinated PCR with ABI sequence analyzer demonstrated that 41% of pts had high levels of MSI in four or more of 10 microsatellite loci. Immunohistochemistry demonstrated reduced expression of MSH2 and MLH1 in 6/10 pts with MSI as compared to 0/5 of pts without MSI. In conclusion, genetic predisposition as well as epigenetic events contribute to the etiology of t-AML/MDS.
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PMID:Therapy-related leukemia: clinical characteristics and analysis of new molecular risk factors in 96 adult patients. 1616 58

Mutations of the FLT3, c-KIT, c-FMS, KRAS, NRAS, BRAF and CEBPA genes in the receptor tyrosine kinase (RTK)/RAS-BRAF signal-transduction pathway are frequent in acute myeloid leukemia (AML). We examined 140 patients with therapy-related myelodysplasia or AML (t-MDS/t-AML) for point mutations of these seven genes. In all, 11 FLT3, two c-KIT, seven KRAS, eight NRAS and three BRAF mutations were identified in 29 patients (21%). All but one patient with a FLT3 mutation presented with t-AML (P=0.0002). Furthermore, FLT3 mutations were significantly associated with previous radiotherapy without chemotherapy (P=0.03), and with a normal karyotype (P=0.004), but inversely associated with previous therapy with alkylating agents (P=0.003) and with -7/7q- (P=0.001). RAS mutations were associated with AML1 point mutations (P=0.046) and with progression from t-MDS to t-AML (P=0.008). Noteworthy, all three patients with BRAF mutations presented as t-AML of M5 subtype with t(9;11)(p22;q23) and MLL-rearrangement (P=0.01). In t-AML RAS/BRAF mutations were significantly associated with a very short survival (P=0.017). Half of the patients with a mutation in the RTK/RAS-BRAF signal-transduction pathway (denoted 'class-I' mutations) simultaneously disclosed mutation of a hematopoietic transcription factor (denoted 'class-II' mutations) (P=0.046) suggesting their cooperation in leukemogenesis.
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PMID:Mutations of genes in the receptor tyrosine kinase (RTK)/RAS-BRAF signal transduction pathway in therapy-related myelodysplasia and acute myeloid leukemia. 1628 Oct 72

Activating tyrosine kinase (TK) mutations disrupt cellular proliferation and survival pathways and are increasingly recognized as a fundamental cause of human cancers. Until very recently, the only TK mutations widely observed in myeloid neoplasia were the BCR/ABL1 fusions characteristic of chronic myeloid leukemia and some acute leukemias, and FLT3 activating mutations in a minority of acute myeloid leukemias. Several rare TK mutations are found in various atypical myeloproliferative disorders, but big pieces of the pathobiological puzzle were glaringly missing. In the first half of 2005, one gap was filled in: 7 studies identified the same acquired amino acid substitution (V617F) in the Janus kinase 2 (JAK2) TK in large numbers of patients with diverse clonal myeloid disorders. Most affected patients suffer from the classic BCR/ABL1-negative myeloproliferative disorders (MPD), especially polycythemia vera (74% of n = 506), but a subset of people with essential thrombocythemia (36% of n = 339) or myelofibrosis with myeloid metaplasia (44% of n = 127) bear the identical mutation, as do a few individuals with myelodysplastic syndromes or an atypical myeloid disorder (7% of n = 556). This long-sought common mutation in BCR/ABL1-negative MPD raises many provocative biological and clinical questions, and demands re-evaluation of prevailing diagnostic algorithms for erythrocytosis and thrombocytosis. JAK2 V617F may provide novel molecular targets for drug therapy, and suggests other places to seek cooperating mutations or mutations associated with similar phenotypes. The story of this exciting finding will unfold rapidly in the years ahead, and ongoing developments will be important for all hematologists to understand.
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PMID:JAK2 V617F in myeloid disorders: what do we know now, and where are we headed? 1632 48

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

AML1/RUNX1 mutations have been reported frequently in myelodysplastic syndrome (MDS) patients, especially those diagnosed with refractory anemia with excess blast (RAEB), RAEB in transformation (RAEBt), or AML following MDS (these categories are defined as MDS/AML). Although AML1 mutations are suspected to play a pivotal role in the development of MDS/AML, acquisition of additional genetic alterations is also necessary. We analyzed gene alterations in MDS/AML patients with AML1 mutations, comparing them to alterations in those without an AML1 mutation. AML1 mutations were significantly associated with -7/7q-, whereas MDS/AML patients without AML1 mutations showed a high frequency of -5/5q- and a complex karyotype. Patients with AML1 mutations showed more mutations of their FLT3, N-RAS, PTPN11, and NF1 genes, resulting in a significantly higher mutation frequency for receptor tyrosine kinase (RTK)-RAS signaling pathways in AML1-mutated MDS/AML patients compared to AML1-wild-type MDS/AML patients (38% versus 6.3%, P < 0.0001). Conversely, p53 mutations were detected only in patients without AML1 mutations. Furthermore, blast cells of the AML1-mutated patients expressing surface c-KIT, and SHP-2 mutants contributed to prolonged and enhanced extracellular signal-regulated kinase activation following stem cell factor stimulation. Our results suggest that MDS/AML arising from AML1/RUNX1 mutations has a significant association with -7/7q- alteration, and frequently involves RTK-RAS signaling pathway activation.
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PMID:Hyperactivation of the RAS signaling pathway in myelodysplastic syndrome with AML1/RUNX1 point mutations. 1646 64


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