Notch-1 regulates cell death independently of differentiation in murine erythroleukemia cells through multiple apoptosis and cell cycle pathways.
Notch signaling is a potential therapeutic target for various solid and hematopoietic malignancies. We have recently shown that downregulation of Notch-1 expression has significant anti-neoplastic activity in pre-clinical models. However, the mechanisms through which Notch modulation may affect cell fate in cancer remain poorly understood. We had previously shown that Notch-1 prevents apoptosis and is necessary for pharmacologically induced differentiation in murine erythroleukemia (MEL) cells. We investigated the mechanisms of these effects using three experimental strategies: (1) MEL cells stably transfected with antisense Notch-1 or constitutively active Notch-1, (2) activation of Notch-1 by a cell-associated ligand, and (d3) activation of Notch-1 by a soluble peptide ligand. We show that: (1) downregulation of Notch-1 sensitizes MEL cells to apoptosis induced by a Ca(2+) influx or anti-neoplastic drugs; (2) Notch-1 downregulation induces phosphorylation of c-Jun N-terminal kinase (JNK) while constitutive activation of Notch-1 or prolonged exposure to a soluble Notch ligand abolishes it; (3) Notch-1 has dose- and time-dependent effects on the levels of apoptotic inhibitor Bcl-x(L) and cell cycle regulators p21(cip1/waf1), p27(kip1), and Rb; and (4) Notch-1 activation by a cell-associated ligand is accompanied by rapid and transient induction of NF-kappaB DNA-binding activity. The relative effects of Notch-1 signaling on these pathways depend on the levels of Notch-1 expression, the mechanism of activation, and the timing of activation. The relevance of these findings to the role of Notch signaling in differentiation and cancer are discussed.
Jang
Mei-Shiang
MS
Cardinal Bernardin Cancer Center, Loyola University Chicago, Maywood, Illinois, USA.
Miao
Haixi
H
Carlesso
Nadia
N
Shelly
Leslie
L
Zlobin
Andrei
A
Darack
Nicole
N
Qin
Jian-Zhong
JZ
Nickoloff
Brian J
BJ
Miele
Lucio
L
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D048031:JNK Mitogen-Activated Protein Kinases; D004915:Leukemia, Erythroblastic, Acute / Q000503:physiopathology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C497762:Notch1 protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D051020:bcl-X Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases