hes1-protein--human and Leukemia--Erythroblastic--Acute

Notch signaling regulates the fate of hematopoietic stem cells and leukemia cells. However, the role of Notch in erythroid differentiation remains unclear.. We examined the effects of three γ-secretase inhibitors (GSI-IX, GSI-XII and GSI-XXI) that inhibit Notch signaling on the in vitro growth and differentiation of HEL and AA erythroid leukemia cell lines.. GSI treatment induced morphologic erythroid differentiation and promoted hemoglobin production. GSI treatment suppressed short-term growth and colony formation, while treatment with GSI-XXI promoted the growth of AA cells. The degree of differentiation induced by each GSI roughly correlated with the reduction in HES1 mRNA expression.. GSIs have potential uses in differentiation induction therapy for erythroid leukemia in the future. Before clinical use, in vitro sensitivity tests should be performed because the effects of GSIs are diverse depending upon the combination of leukemia cells and GSIs.

Topics: Aged; Amyloid Precursor Protein Secretases; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; Cell Growth Processes; Cell Line, Tumor; Dipeptides; Erythroid Cells; Gene Expression; Homeodomain Proteins; Humans; Leukemia, Erythroblastic, Acute; Male; Neoplastic Stem Cells; Protease Inhibitors; Transcription Factor HES-1

Notch signaling is involved in cell fate decisions in many systems including hematopoiesis. It has been shown that expression of an activated form of Notch1 (aNotch1) in 32D mouse myeloid progenitor cells inhibits the granulocytic differentiation induced by granulocyte colony-stimulating factor (G-CSF). Results of the current study show that aNotch1, when expressed in F5-5 mouse erythroleukemia cells, also inhibits erythroid differentiation. Comparison of the expression levels of several transcription factors after stimulation for myeloid and erythroid differentiation, in the presence or absence of aNotch1, revealed that aNotch1 did not change its regulation pattern with any of the transcription factors examined, except for GATA-2, despite its inhibitory effect on differentiation. GATA-2 was down-regulated when the parental 32D and F5-5 were induced to differentiate into granulocytic and erythroid lineages, respectively. In these induction procedures, however, the level of GATA-2 expression was sustained when aNotch1 was expressed. To ascertain whether maintenance of GATA-2 is required for the Notch-induced inhibition of differentiation, the dominant-negative form of GATA-3 (DN-GATA), which acted also against GATA-2, or transcription factor PU.1, which was recently shown to be the repressor of GATA-2, was introduced into aNotch1-expressing 32D (32D/aNotch1) cells that do not express GATA family proteins other than GATA2. Both DN-GATA and PU.1 reversed the phenotype of 32D/aNotch1 inducing its differentiation when G-CSF was added. Furthermore, enforced expression of HES-1, which is involved in Notch signaling, delayed differentiation of 32D, and again this phenotype was neutralized by DN-GATA. These results indicate that GATA-2 activity is necessary for the Notch signaling in hematopoietic cells.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; DNA-Binding Proteins; Erythrocytes; GATA2 Transcription Factor; Gene Expression Regulation; Granulocyte Colony-Stimulating Factor; Granulocytes; Hematopoietic Stem Cells; Homeodomain Proteins; Humans; Leukemia, Erythroblastic, Acute; Membrane Proteins; Mice; Phenotype; Proto-Oncogene Proteins; Receptor, Notch1; Receptors, Cell Surface; Reverse Transcriptase Polymerase Chain Reaction; Trans-Activators; Transcription Factor HES-1; Transcription Factors; Tumor Cells, Cultured