The expression of immediate early gene X-1 (IEX-1) is differentially induced by retinoic acids in NB4 and KG1 cells: possible implication in the distinct phenotype of retinoic acid-responsive and -resistant leukemic cells.
In a cell-type- and stimulus-dependent fashion, the early response gene immediate early gene X-1 (IEX-1) is involved in growth control and modulation of apoptosis. The present study demonstrates that, in the two acute promyelocytic leukemia (APL) cell lines NB4 and KG1, exhibiting distinct responsiveness to retinoic acids (RAs), IEX-1 expression is rapidly (30-60 min) induced by all-trans- or cis-RA and independently of other signal transduction mediators, such as TNFalpha, NF-kappaB or MAP kinases. In NB4 cells (expressing PML-RARalpha), this increase is transient and completely reversible, along with a cell cycle arrest, ongoing differentiation and lower sensitivity to anti-cancer-drug-induced apoptosis. In contrast, the RA-induced IEX-1 expression in KG1 cells (expressing PLZF-RARalpha) persists over days, along with continued cell cycle progression and increased apoptotic sensitivity. Furthermore, two functional RA-response elements in the IEX-1 promoter were identified by gel shift and luciferase reporter gene assays. IEX-1 might be a rather unique transcriptional target of the two X-RARalpha fusion receptors exhibiting distinct responsiveness to RAs. Following a different time course of direct transcriptional induction by PML-RARalpha and PLZF-RARalpha in NB4 and KG1 cells, respectively, IEX-1 expression may be involved in the modified actions of these receptors and the distinct phenotypes of APL cells.
Division of Molecular Gastroenterology & Hepatology, 1st Department of Medicine, Christian-Albrechts-University, Kiel, Germany.
A
A
Arlt
J
J
Minkenberg
B
B
Kocs
M
M
Grossmann
M-L
ML
Kruse
U R
UR
Fölsch
H
H
Schäfer
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D024202:Electrophoretic Mobility Shift Assay; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D008565:Membrane Proteins; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D010641:Phenotype; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; C118318:PLZF-RARalpha fusion protein, human; C093476:promyelocytic leukemia-retinoic acid receptor alpha fusion oncoprotein; D014212:Tretinoin; D008156:Luciferases