12th Congress of the European Hematology ... - Haematologica

of erythroid colonies was reduced in NF-E2 overexpressing cells. Xu et
al. have previously reported a similar reduction in cloning efficiency of
Idiopathic Myelofibrosis CD34 + cells, which have been shown to overexpress
NF-E2. NF-E2 overexpression lead to a delay in erythroid differentiation,
manifested by a belated appearance of CD235a (Glycophorin
A) positive mature erythroid cells. Morphological evaluation similarly
revealed more immature cells in NF-E2 overexpressing cultures. Protracted
differentiation lead to a significant increase in the accumulated number
of mature erythroid cells per progenitor cell. Summary and conclusions.
NF-E2 overexpression delays the early phase of erythroid differentiation.
This results in an expansion of early erythroid progenitors, thereby
increasing the total number of mature erythrocytes derived from one
CD34 + cell. These data propose a role for NF-E2 in mediating the erythrocytosis
of PV.
0240
STEPWISE TRANSFORMATION OF PRIMARY BONE MARROW PROGENITOR CELLS EX
VIVO
M. Scherr, 1 Y. Dogan, 1 G. Beutel, 1 K. Battmer, 1 L. Venturini, 1
D. Schaefer, 1 L. Wilkens, 2 A. Ganser, 1 M. Eder1 1 2 Hannover Medical School, HANNOVER, Germany; University of Bern,
BERN, Switzerland
Background. Leukemogenesis is considered a multistep process of accumulating
genetic alterations in hematopoietic stem or progenitor cells.
Current experimental models using established cell lines or murine stem
cell transplantation assays do not sufficiently allow investigation of the
cooperative effects of defined genetic alterations. Aims. We established
immortalized cell lines from murine bone marrow to study their stepwise
progression into more transformed phenotypes. Methods and
Results.Primary murine lineage negative bone marrow cells were retrovirally
transduced to express either AML1-ETO or HoxB4 along with
EGFP as a quantitative reporter under serum free conditions in the presence
of SCF+IL-3+IL-6. Immortalized EGFP+ cell lines could be established
in both conditions. The resulting cell lines are dependent on
expression of the respective transgene but show strikingly different phenotypes.
First, long-term cultures for AML1-ETO remain strictly SCFdependent,
whereas HoxB4 cultures only require IL-3 for cell survival and
proliferation. Secondly, AML1-ETO but not HoxB4 cells express c-Kit
and Sca-1 on more than 90% of the cells with a high proportion of side
population (SP) cells. In addition, AML1-ETO cells form only blast like
colonies with very low plating efficiency (