Contribution of STAT3 to the activation of survivin by GM-CSF in CD34+ cell lines.
OBJECTIVE
Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to specifically stimulate proliferation of CD34(+) hematopoietic progenitor cells. Although signal transducers and activators of transcription 3 (STAT3) is believed essential for transduction of GM-CSF-induced cell proliferation, the signaling mediated by STAT3 is not completely understood. Because survivin regulates cell proliferation and survival via its antiapoptotic function, we studied the link between STAT3 signaling and survivin expression in CD34(+) cells.


METHODS
GM-CSF-induced STAT3 and survivin expression in CD34(+) cells was examined by Western blot assay. GM-CSF-activated survivin promoter activity was analyzed by gene transfection and reporter assays. The binding of STAT3 to the survivin promoter was evaluated by chromatin immunoprecipitation and electrophoretic mobility shift assay. Western blotting and flow cytometry were utilized to test the effect of Janus family of tyrosine kinases (JAK) inhibitor and STAT3 small interfering RNA (siRNA) on cell apoptosis.


RESULTS
We found that GM-CSF stimulates survivin promoter activity in CD34(+) KG-1 cells, and STAT3 binds to the core survivin promoter containing a STAT response element TT(N)(5)AA at sites -264 to -256. Mutation or deletion of this STAT response element completely abolished the effects of GM-CSF on survivin promoter activity. Furthermore, addition of either JAK inhibitor or STAT3 siRNA was able to inhibit GM-CSF-induced survivin promoter activity and survivin expression. Inhibition of survivin by STAT3 siRNA or by withdrawal of GM-CSF in a GM-CSF-dependent, CD34(+) line TF-1 decreased cell growth and increased apoptosis.


CONCLUSIONS
Altogether, our results suggest that survivin is a transcriptional target of STAT3, and that GM-CSF-stimulated CD34(+) cell proliferation is regulated by the JAK/STAT3/survivin signaling pathway.
Gu
Lubing
L
Division of Pediatric Hematology/Oncology, Aflac Cancer Center and Blood Disorders Service, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA.
Chiang
Kuang-Yueh
KY
Zhu
Ningxi
N
Findley
Harry W
HW
Zhou
Muxiang
M
D018952:Antigens, CD34; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D053612:Janus Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis* / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D000077022:Survivin
D018952:Antigens, CD34; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D000077022:Survivin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D053612:Janus Kinases