The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells.
BACKGROUND
The fusion protein RUNX1-CBFA2T1 associated with t(8;21)-positive acute myeloid leukaemia is a potent inhibitor of haematopoetic differentiation. The role of RUNX1-CBFA2T1 in leukaemic cell proliferation is less clear. We examined the consequences of siRNA-mediated RUNX1-CBFA2T1 depletion regarding proliferation and clonogenicity of t(8;21)-positive cell lines.


METHODS
The t(8;21)-positive cell line Kasumi-1 was electroporated with RUNX1-CBFA2T1 or control siRNAs followed by analysis of proliferation, colony formation, cell cycle distribution, apoptosis and senescence.


RESULTS
Electroporation of Kasumi-1 cells with RUNX1-CBFA2T1 siRNAs, but not with control siRNAs, resulted in RUNX1-CBFA2T1 suppression which lasted for at least 5 days. A single electroporation with RUNX1-CBFA2T1 siRNA severely diminished the clonogenicity of Kasumi-1 cells. Prolonged RUNX1-CBFA2T1 depletion inhibited proliferation in suspension culture and G1-S transition during the cell cycle, diminished the number of apoptotic cells, but induced cellular senescence. The addition of haematopoetic growth factors could not rescue RUNX1-CBFA2T1-depleted cells from senescence, and could only partially restore their clonogenicity.


CONCLUSIONS
RUNX1-CBFA2T1 supports the proliferation and expansion of t(8;21)-positive leukaemic cells by preventing cellular senescence. These findings suggest a central role of RUNX1-CBFA2T1 in the maintenance of the leukaemia. Therefore, RUNX1-CBFA2T1 is a promising and leukaemia-specific target for molecularly defined therapeutic approaches.
Department of Molecular Biology, Institute for Cell Biology, Faculty of Biology, University of Tübingen, Germany. natalia.martinez@uni-tuebingen.de
Natalia
N
Martinez
Bettina
B
Drescher
Heidemarie
H
Riehle
Claire
C
Cullmann
Hans-Peter
HP
Vornlocher
Arnold
A
Ganser
Gerhard
G
Heil
Alfred
A
Nordheim
Jürgen
J
Krauter
Olaf
O
Heidenreich
D018952:Antigens, CD34 / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics*; D002999:Clone Cells; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins / Q000502:physiology*; D006410:Hematopoiesis / Q000235:genetics; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics* / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D000075142:RUNX1 Translocation Partner 1 Protein; D014157:Transcription Factors / Q000502:physiology*; D014407:Tumor Cells, Cultured
D018952:Antigens, CD34; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D000075142:RUNX1 Translocation Partner 1 Protein; C493728:RUNX1 protein, human; C082222:RUNX1T1 protein, human; D014157:Transcription Factors