To investigate the molecular effects of growth factor independence 1B (Gfi-1B), 
a transcription factor essential for the development of hematopoietic cells and 
differentiation of erythroid and megakaryocytic lineages, the naturally Gfi-1B 
overexpressing cell line K562 was cultured in the presence of Gfi-1B 
target-specific small interfering RNA (siRNA). SiRNA treatment significantly 
knocked down Gfi-1B expression with an efficiency of nearly 90%. Analysis of the 
siRNA silencing protocol by colony-forming units ensured that it was not 
cytotoxic. Samples from Gfi-1B overexpressing cells and cells with knocked-down 
Gfi-1B were analyzed by oligonucleotide microarray technology and based upon 
rigorous statistical analysis of the data; relevant genes were chosen for 
confirmation by reserve transcriptase-polymerase chain reaction, including 
MYC/MYCBP and CDKN1A. Interestingly, transcripts within components of the 
signalling cascade of immune cells (PLD1, LAMP1, HSP90, IL6ST), of the tyrosine 
kinase pathway (TPR, RAC3) and of the transcription factors (RAC3, CEP290, 
JEM-1, ATR, MYC, SMC3, RARA, RBBP6) were found to be differentially expressed in 
Gfi-1B overexpressing cells compared to controls. Individual genes such as 
ZDHHC17, DMXL1, ZNF292 were found to be upregulated in Gfi-1B overexpressing 
cells. In addition, down-regulated transcripts showed cell signaling transcripts 
for several chemokine gene members including GNAL, CXCL5, GNL3L, GPR65, TMEM30, 
BCL11B and transcription factors (GTF2H3, ATXN3). In conclusion, several 
essential cell signalling factors, as well as transcriptional and 
post-translational regulation genes were differentially expressed in cells that 
overexpressed Gfi-1B compared to control cells with knocked-down Gfi-1B. Our 
data indicate that Gfi-1B signalling is important for commitment and maturation 
of hematopoietic cell populations.