Transcriptional repression of c-Myb and GATA-2 is involved in the biologic effects of C/EBPalpha in p210BCR/ABL-expressing cells.
Ectopic C/EBPalpha expression in p210(BCR/ABL)-expressing hematopoietic cells induces granulocytic differentiation, inhibits proliferation, and suppresses leukemogenesis. To assess the underlying mechanisms, C/EBPalpha targets were identified by microarray analyses. Upon C/EBPalpha activation, expression of c-Myb and GATA-2 was repressed in 32D-BCR/ABL, K562, and chronic myelogenous leukemia (CML) blast crisis (BC) primary cells but only c-Myb levels decreased slightly in CD34(+) normal progenitors. The role of these 2 genes for the effects of C/EBPalpha was assessed by perturbing their expression in K562 cells. Ectopic c-Myb expression blocked the proliferation inhibition- and differentiation-inducing effects of C/EBPalpha, whereas c-Myb siRNA treatment enhanced C/EBPalpha-mediated proliferation inhibition and induced changes in gene expression indicative of monocytic differentiation. Ectopic GATA-2 expression suppressed the proliferation inhibitory effect of C/EBPalpha but blocked in part the effect on differentiation; GATA-2 siRNA treatment had no effects on C/EBPalpha induction of differentiation but inhibited proliferation of K562 cells, alone or upon C/EBPalpha activation. In summary, the effects of C/EBPalpha in p210(BCR/ABL)-expressing cells depend, in part, on transcriptional repression of c-Myb and GATA-2. Since perturbation of c-Myb and GATA-2 expression has nonidentical consequences for proliferation and differentiation of K562 cells, the effects of C/EBPalpha appear to involve dif-ferent transcription-regulated targets.
Department of Cancer Biology, Kimmel Cancer Center, Thomas Jefferson Medical College, Philadelphia, PA 19107, USA.
Angela Rachele
AR
Soliera
Maria Rosa
MR
Lidonnici
Giovanna
G
Ferrari-Amorotti
Marco
M
Prisco
Ying
Y
Zhang
Robert V
RV
Martinez
Nick J
NJ
Donato
Bruno
B
Calabretta
D001483:Base Sequence; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism / Q000494:pharmacology*; D002453:Cell Cycle; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis* / Q000235:genetics; D050989:GATA2 Transcription Factor / Q000235:genetics*; D016313:Genes, abl; D020570:Genes, myb / Q000187:drug effects*; D006801:Humans; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D022763:CCAAT-Enhancer-Binding Protein-alpha; D017931:DNA Primers; D050989:GATA2 Transcription Factor; C494711:GATA2 protein, human; D034741:RNA, Small Interfering; D016044:Fusion Proteins, bcr-abl