Many human myeloid leukemia-derived cell lines possess the ability to acquire a dendritic cell (DC) phenotype. However, cytokine responsiveness is generally poor, requiring direct manipulation of intracellular signaling mechanisms for differentiation. In contrast, the CD34 ؉ human acute myeloid leukemia cell line MUTZ-3 responds to granulocyte macrophagecolony-stimulating factor (GM-CSF), interleukin 4 (IL-4), and tumor necrosis factor alpha (TNF␣), cytokines known to be pivotal both in vivo and in vitro for DC generation from monocytes and CD34 ؉ stem cells. In all respects, MUTZ-3 cells behave as the immortalized equivalent of CD34 ؉ DC precursors. Upon stimulation with specific cytokine cocktails, they acquire a phenotype consistent with either interstitial-or Langerhans-like DCs and upon maturation (mDC), express CD83. MUTZ-3 DC display the full range of functional antigen processing and presentation pathways. These findings demonstrate the unique suitability of MUTZ-3 cells as an unlimited source of CD34 ؉ DC progenitors for the study of cytokineinduced DC differentiation. 3,4 However, the currently defined culture protocols require long expansion periods, given the relative scarcity of blood DC precursors, and involve the use of extensive cytokine cocktails. [5][6][7][8] Therefore, a human cell line exhibiting the characteristics of CD34 ϩ -derived DC precursors would allow for the detailed study of DC differentiation without the associated problems of donor variability and DC precursor cell availability. It has been observed that cell lines derived from tumors of lymphoid or myeloid lineage may also share a potential for differentiation to DC-like APCs, thus providing a ready supply of DC precursors from which DCs can be easily and routinely generated. However, many leukemia cell lines are often refractory to cytokine treatment, 9,10 requiring pharmacologic agents to induce a DC-like phenotype in myeloid cells, bypassing important checkpoints in the differentiation of DCs. 9,10 In contrast, it has been reported that the human cytokine-dependent myeloid cell line MUTZ-3 downregulates CD14 in response to interleukin 4 (IL-4) and low-level granulocyte macrophage-colony-stimulating factor (GM-CSF). 11,12 Here we demonstrate that this cell line is unique in its capacity to acquire a cytokine-induced interstitial and LC iDC phenotype, thus providing a rapid, logistically reproducible model for studies of the immunomodulatory capacity of DCs and such DC-related processes as antigen processing and presentation.
Study design
Generation of iDC-and mDC-like cells from leukemia cell linesThe cytokine-dependent human cell line MUTZ-3 (Deutsche Sammlung von Mikroorganismen und Zellkulturen [DSMZ], Braunschweig, Germany), and the cytokine-independent human cell lines, HL-60, KG-1, THP-1 U937, and K562 (American Type Culture Collection [ATCC], Manassas, VA) were cultured at 1 ϫ 10 5 /mL (total volume of 2.5 mL) in 12-well tissue culture plates (Costar, Cambridge, MA) in the presence of GM-CSF (100 ng/mL; Novartis/Scheri...