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

Current investigations have revealed that angiogenesis plays a role in the pathogenesis of high-risk myelodysplastic syndrome (MDS) and acute myeloid leukemia, and in the mechanisms of disease progression. Secretion of cytokines and growth factors modulates angiogenesis in the marrow leading to increased vascularity and sustenance of the clonal population. For high-risk MDS patients older than 60 years who are not eligible for aggressive chemotherapy or stem cell transplant, there are few therapeutic options other than supportive treatment. Recent delineation of the pathobiology of MDS has resulted in the development of new agents and treatment modalities that impact on these mechanisms. One of the features of bone marrow pathology is the presence of new vessels, which appear to sustain growth and the hypercellularity of the marrow. Blocking angiogenesis may reduce the microvessel density of the marrow, cellularity, and disease progression. Angiogenesis can be targeted by inhibition of vascular endothelial growth factor (VEGF), which modulates new vessel growth, by the use of antibodies aimed at VEGF and its receptors, as well as receptor tyrosine kinases that block VEGF signaling. Other agents include inhibitors of farnesyl transferase and protein kinase C, which affect upstream modulators of growth factors and their receptor interactions; matrix metalloproteinases, which disrupt matrices and adhesion function promoting vessel growth; and other inhibitors with broader function, such as endostatin, thalidomide, and related analogues.
 ...
PMID:Modulation of angiogenesis in patients with myelodysplastic syndrome. 1549 99

Programmed cell death or apoptosis is a prominent feature of low-risk myelodysplastic syndromes (MDS), although the underlying mechanism remains controversial. High-risk MDS have less apoptosis associated with increased expression of the prosurvival BCL2-related proteins. To address the mechanism and pathogenic role of apoptosis and BCL2 expression in MDS, we used a mouse model resembling human MDS, in which the fusion protein NUP98-HOXD13 (NHD13) of the chromosomal translocation t(2;11)(q31;p15) is expressed in hematopoietic cells. Hematopoietic stem and progenitor cells from 3-month-old mice had increased rates of apoptosis associated with increased cell cycling and DNA damage. Gene expression profiling of these MDS progenitors revealed a specific reduction in Bcl2. Restoration of Bcl2 expression by a BCL2 transgene blocked apoptosis of the MDS progenitors, which corrected the macrocytic anemia. Blocking apoptosis also restored cell-cycle quiescence and reduced DNA damage in the MDS progenitors. We expected that preventing apoptosis would accelerate malignant transformation to acute myeloid leukemia (AML). However, contrary to expectations, preventing apoptosis of premalignant cells abrogated transformation to AML. In contrast to the current dogma that overcoming apoptosis is an important step toward cancer, this work demonstrates that gaining a survival advantage of premalignant cells may delay or prevent leukemic progression.
 ...
PMID:Inhibition of apoptosis by BCL2 prevents leukemic transformation of a murine myelodysplastic syndrome. 2285 10

Myelodysplastic syndromes (MDS) are a group of disorders characterized by variable cytopenias and ineffective hematopoiesis. Hematopoietic stem cells (HSCs) and myeloid progenitors in MDS have not been extensively characterized. We transplanted purified human HSCs from MDS samples into immunodeficient mice and show that HSCs are the disease-initiating cells in MDS. We identify a recurrent loss of granulocyte-macrophage progenitors (GMPs) in the bone marrow of low risk MDS patients that can distinguish low risk MDS from clinical mimics, thus providing a simple diagnostic tool. The loss of GMPs is likely due to increased apoptosis and increased phagocytosis, the latter due to the up-regulation of cell surface calreticulin, a prophagocytic marker. Blocking calreticulin on low risk MDS myeloid progenitors rescues them from phagocytosis in vitro. However, in the high-risk refractory anemia with excess blasts (RAEB) stages of MDS, the GMP population is increased in frequency compared with normal, and myeloid progenitors evade phagocytosis due to up-regulation of CD47, an antiphagocytic marker. Blocking CD47 leads to the selective phagocytosis of this population. We propose that MDS HSCs compete with normal HSCs in the patients by increasing their frequency at the expense of normal hematopoiesis, that the loss of MDS myeloid progenitors by programmed cell death and programmed cell removal are, in part, responsible for the cytopenias, and that up-regulation of the "don't eat me" signal CD47 on MDS myeloid progenitors is an important transition step leading from low risk MDS to high risk MDS and, possibly, to acute myeloid leukemia.
 ...
PMID:Hematopoietic stem cell and progenitor cell mechanisms in myelodysplastic syndromes. 2338 39