Expression of p15(ink4b) gene during megakaryocytic differentiation of normal and myelodysplastic hematopoietic progenitors.
In myelodysplastic syndrome (MDS), the expression of the cyclin-dependent kinase inhibitor p15(ink4B) (p15) is frequently decreased because of the aberrant methylation of the gene promoter; p15 is normally up-regulated during megakaryocytic differentiation. It was hypothesized that p15 methylation and deregulation of gene expression contribute to defective megakaryocytopoiesis in patients with MDS. Here it is shown that the increasing autocrine production of TGF-beta1 stimulates megakaryocytic differentiation in normal CD34(+) cells and that p15 mediates, at least in part, this effect. This TGF-beta1-dependent pathway is altered in MDS CD34(+) progenitors because of p15 methylation. The demethylating agent 2-deoxyAZAcytidin can restore the normal demethylated state of the p15 gene and increase its expression. Nevertheless, MDS CD34(+) cells only poorly differentiate to the megakaryocytic lineage. These findings suggest that p15 methylation occurs in a neoplastic clone with a profound defect of cell proliferation, survival, and differentiation that cannot be overcome by using a demethylating drug.
Teofili
L
L
Institutes of Hematology and Pathology, Università Cattolica del Sacro Cuore, Rome, Italy.
Martini
M
M
Di Mario
A
A
Rutella
S
S
Urbano
R
R
Luongo
M
M
Leone
G
G
Larocca
L M
LM
D000754:Anemia, Refractory, with Excess of Blasts / Q000473:pathology; D018952:Antigens, CD34 / Q000032:analysis; D001854:Bone Marrow Cells / Q000276:immunology; D002352:Carrier Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D002455:Cell Division; D002469:Cell Separation; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D019175:DNA Methylation; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D008533:Megakaryocytes / Q000737:chemistry / Q000473:pathology*; D009190:Myelodysplastic Syndromes / Q000235:genetics* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013926:Thrombopoietin / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D025521:Tumor Suppressor Proteins
D018952:Antigens, CD34; C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D015850:Interleukin-6; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D013926:Thrombopoietin