A new cytokine-dependent monoblastic cell line with t(9;11)(p22;q23) differentiates to macrophages with macrophage colony-stimulating factor (M-CSF) and to osteoclast-like cells with M-CSF and interleukin-4.

Monocytes/macrophages exert a series of important functions in vivo. To facilitate detailed investigation of their functional capacity and the mechanism leading to their differentiation, several cell lines have been established from primary material. We present here a new human monoblastic cell line, designated UG3. UG3 cells are characterized by the following features. (1) UG3 cells harbor the t(9;11)(p22;q23) translocation that results in fusion of the MLL and the AF9 genes and produce the corresponding AF9-MLL and MLL-AF9 fusion transcripts. (2) UG3 cells rely on the presence of exogenous growth factors for viability and proliferation, such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), or macrophage colony-stimulating factor (M-CSF). (3) When cultured in the presence of G-CSF, UG3 cells differentiate along the granulocytic lineage, as evidenced by segmentation of nuclei and positive staining for neutrophilic alkaline phosphatase and peroxidase. (4) When cultured in the presence of GM-CSF or M-CSF, UG3 cells differentiate into mature macrophages while preserving surface expression of CD14 and CD68 and also start to release cytokines into cell-culture supernatants. Under these culture conditions, UG3 cells also take up acetylated LDL. (5) When cultured in the presence of M-CSF and IL-4, UG3 cells differentiate into osteoclast-like multinucleated giant cells capable of bone resorption and display tartrate-resistant acid phosphatase (TRAP) activity. UG3 cells thus provide features to qualify them as a useful model to further investigate the mechanism underlying these processes and also to further elucidate the functional role of mature monocytes/macrophages or osteoclasts.