Enforced adenoviral vector-mediated expression of HOXB4 in human umbilical cord blood CD34+ cells promotes myeloid differentiation but not proliferation.
Retroviral overexpression of the transcription factor HOXB4 results in a rapid increase in proliferation of murine hematopoietic stem cells both in vivo and in vitro. Therefore, we asked whether transient overexpression of HOXB4 would increase proliferation of human primitive hematopoietic progenitors. Transient overexpression of HOXB4 was generated in umbilical cord blood (CB) CD34(+) cells by a recombinant adenovirus (AdHOXB4) expressing HOXB4 together with the enhanced green fluorescent protein (GFP). Transduced, GFP(+) cells were cultured in serum-free medium containing cytokines that primarily support the growth of primitive hematopoietic progenitors. In contrast to previous findings using retroviral overexpression of HOXB4, we did not observe any increase in proliferation of primitive progenitors or increased colony formation of clonogenic progenitors, including progenitor progeny from long-term culture-initiating cells following adenoviral vector overexpression of HOXB4 in CB CD34(+) cells. However, enforced expression of HOXB4 by the adenoviral vector significantly increased myeloid differentiation of primitive hematopoietic progenitors. Since retroviral vectors generate low and continuous levels of transgene expression in contrast to the high, transient levels generated by the adenoviral vector, our findings suggest that the high levels of HOXB4 expression generated by AdHOXB4 in human CB CD34(+) cells direct the cells toward a myeloid differentiation program rather than increased proliferation.
Brun
Ann C M
AC
Department of Molecular Medicine and Gene Therapy, Lund University Hospital, 221 84 Lund, Sweden. Ann.Brun@molmed.lu.se
Fan
Xiaolong
X
Björnsson
Jon Mar
JM
Humphries
R Keith
RK
Karlsson
Stefan
S
D000256:Adenoviridae; D018952:Antigens, CD34 / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D005312:Fetal Blood / Q000166:cytology / Q000378:metabolism; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D022423:Myeloid Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D018952:Antigens, CD34; C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; D014157:Transcription Factors