Down-regulation of Notch-1 expression decreases PU.1-mediated myeloid differentiation signaling in acute myeloid leukemia.
The Notch receptor-mediated signaling pathways control cell fate in many types of organisms including neurogenesis, myogenesis and hematopoiesis in mammalian species. During normal hematopoiesis, Notch-1 promotes myeloid differentiation through up-regulation of the transcriptional factor PU.1. We therefore speculated that down-regulation of Notch-1 expression might be involved in the leukemogenesis of acute myeloid leukemia (AML). Here we investigated Notch-1 expression and its association with PU.1-mediated differentiation signaling in AML. The transcriptional level of Notch-1 and PU.1 was evaluated in 6 AML cell lines and 54 AML patient samples using real-time PCR analysis, and Western blot analysis of Notch-1, PU.1 and one of its downstream targets, the M-CSF receptor (MCSFR), was performed to test for confirmation. A significant decrease in the transcription levels of Notch-1 was noted in AML cell lines and patient samples, and decreased Notch-1 protein expression in AML was confirmed by Western blotting. Down-regulation of Notch-1 expression was associated with a decrease in PU.1/MCSFR expression in AML. Co-immunoprecipitation experiments showed that partial disruption of the Notch-1/PU.1 complex was noted in AML cells. No detectable mutation of Notch-1 (ANK, PEST) and PU.1 (PEST, DBD) was noted by PCR-single-strand conformation polymorphism (SSCP) assay. These results suggest that down-regulation of Notch-1 expression decreases PU.1/MCSFR expression and disrupts the Notch-1/PU.1 complex, which may impede the PU.1-mediated myeloid signaling and contribute to the leukemogenesis of AML.
Chen
Po-Min
PM
Division of Hematology-Oncology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan R.O.C.
Yen
Chueh-Chuan
CC
Wang
Wei-Shu
WS
Lin
Yu-Jen
YJ
Chu
Chiau-Jun
CJ
Chiou
Tzeon-Jye
TJ
Liu
Jin-Hwang
JH
Yang
Muh-Hwa
MH
D000328:Adult; D000368:Aged; D015153:Blotting, Western; D002454:Cell Differentiation; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D000099232:Proto-Oncogene Protein Spi-1
D011518:Proto-Oncogene Proteins; D051881:Receptor, Notch1; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C497761:NOTCH1 protein, human