ABSTRACT. Leukemia stem cells (LSCs) are regarded as the origin of leukemia and its recurrence. Side population (SP) cells possess some intrinsic stem cell properties and contain numerous LSCs. In this study, we examined the prognostic significance of cluster differentiation 47 (CD47) and identified the appropriate target for eliminating LSCs. We determined the percentage of SP cells in a THP-1 cell population and analyzed CD47 expression in different cell subsets. We then explored whether CD47 affected the phagocytic ability of macrophages to LSCs in vitro. Finally, the effect of anti-CD47 monoclonal antibodies, alone or combination with cytarabine, against leukemic cells was evaluated in vitro and in vivo to identify the optimal targets for the treatment of leukemia. We observed an SP sub-fraction at low frequency (1.81 ± 0.99%), which was a likely candidate for LSC enrichment. CD47 was more highly expressed on THP-1 LSCs (P < 0.05) and was an independent predictor of survival and refractory disease in THP-1-engrafted mice. Furthermore, the anti-CD47 monoclonal antibody stimulated preferential phagocytosis of LSCs by macrophages in vitro. Finally, single or combination treatment of THP-1 LSC-engrafted mice 5631 Combination therapy eliminates leukemic cells ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 5630-5641 (2015) with cytarabine and anti-CD47 antibody resulted in targeting of LSCs and depletion of leukemia cells. These findings suggest that CD47 is an antibody target in LSCs and combination treatment with cytarabine and anti-CD47 monoclonal antibody represents an attractive option for the therapeutic targeting of acute monocytic leukemia.

Aberrant macrophage polarization is a major contributor to the onset and progression of atherosclerosis. Despite this, macrophage polarization during in early stages of human atherosclerotic disease is poorly understood. Using transcriptomic analysis of macrophages recovered from early-stage human atherosclerotic lesions, we have identified a unique gene expression profile dissimilar to that observed in later stages of disease that is characterized by upregulation of the hematopoietic transcription factor GATA2. GATA2 overexpression in vitro recapitulated defects observed in patient macrophages, including deficiencies in the uptake and processing of apoptotic cells, and in the catalysis of atherogenic protein modifications, with GATA2 knockdown abrogating these defects. Our data describe a previously unreported macrophage differentiation state present in early atheroma formation and identifies GATA2 as a driver of macrophage functional defects during the early stages of atherosclerosis in humans.