Submitted February 12, 2009
Accepted June 8, 2009
Reintroduction of CEBPA in MN1-overexpressing hematopoietic cells prevents
their hyper proliferation and restores myeloid differentiation
Ayten Kandilci and Gerard C. Grosveld*
Department of Genetics and Tumor Cell Biology, St Jude Children's Research Hospital, Memphis, TN, United States
* Corresponding author; email: gerard.grosveld{at}stjude.org.
Forced expression of MN1 in primitive mouse hematopoietic cells causes acute myeloid leukemia and impairs all-trans retinoic acid (ATRA) induced granulocytic differentiation. Here, we studied the effects of MN1 on myeloid differentiation and proliferation using primary human CD34+ hematopoietic cells, lineage depleted mouse bone marrow cells, and bipotential (granulocytic/monocytic) human AML-cell lines. We show that exogenous MN1 stimulated the growth of CD34+ cells, which was accompanied by enhanced survival and increased cell cycle traverse in cultures supporting progenitor cell growth. Forced MN1 expression impaired both granulocytic and monocytic differentiation in vitro in primary hematopoietic cells and AML cell lines. Endogenous MN1 expression was higher in human CD34+ cells compared to both primary and in vitro differentiated monocytes and granulocytes. Microarray and real time RT-PCR analysis of MN1-overexpressing CD34+ cells showed down regulation of CEBPA and its downstream target genes. Re-introduction of conditional and constitutive CEBPA overcame the effects of MN1 on myeloid differentiation and inhibited MN1-induced proliferation in vitro. These results indicate that down regulation of CEBPA activity contributes to MN1-modulated proliferation and impaired myeloid differentiation of hematopoietic cells.
