Abstract
The human promyeloid cell line H60 can be induced to differentiate towards either neutrophils or monocytes. Variant cell lines, derived from HL60, which show reduced capacities for neutrophil and monocyte differentiation can be arranged in a developmental sequence which suggests that the potentials for neutrophil and monocyte differentiation are expressed sequentially by HL60 cells in this order. Analysis of the patterns of total cellular phosphoproteins within HL60 and 5 variant cell lines, by two-dimensional gel electrophoresis, has identified 6 distinct phosphoproteins which show progressive differences in the intensity of spots between the variant lines. The changes in these phosphoproteins relate to the position of the lines within the proposed development sequence. Similarly, lines placed close together in the sequence are more similar, as regards phosphoprotein profiles, than lines placed far apart. These studies provide direct evidence in favour of the hypothesis that the potentials for neutrophil and monocyte differentiation are expressed sequentially during myelopoiesis. Furthermore, two phosphoprotein spots were found to be restricted to lines able to differentiate towards monocytes. These proteins may play important roles during commitment to monocyte differentiation.
Highlights
It can be argued that progenitor cells develop lineage potentials sequentially (Brown et al, 1985; 1987) and, for example, during myelopoiesis cells first acquire the capacity for neutrophil maturation and are subsequently able to differentiate towards monocytes (Brown et al, 1985; Dexter et al, 1980)
The phosphoproteins patterns observed in autoradiographs of two-dimensional gels prepared from [32P]-orthophosphate labelled HL60 and variant HL60 cells were complex
The variant cell lines had been ordered in relation to their gradual acquisition of an increased responsiveness to inducers of neutrophil differentiation followed by loss of this potential as cells are committed to monocyte differentiation [Brown et al, 1985 and see Figure 3]
Summary
Cell linesThe promyeloid cell line HL60 was maintained in RPMI 1640 medium (Gibco Ltd., Paisley, Scotland) supplemented with 10% v/v heat inactivated foetal calf serum (Gibco Ltd., Paisley, Scotland), 100 U ml- I penicillin and 100 ,ug ml - 1 streptomycin (Gibco Ltd., Paisley, Scotland). The isolation and characterisation of the variant HL60 cell lines HL60M2, HL6OM4, HL60 Ast and HL60 Ast have been described previously (Toksoz et al, 1982; Bunce et al, 1983). All the variant lines were maintained in the above medium containing 1.25% dimethylsulphoxide (DMSO). This concentration of DMSO induces optimal neutrophil differentiation within HL60 cultures. Neutrophil differentiation is induced in cultures of HL6OM2, HL6OM4, HL60 Ast and HL60 15-12 cells by 1.75% DMSO and HL60 Ast cultures show minimal neutrophil differentiation when treated with 2.0% DMSO. Cells within HL6OAst and HL60Ast cultures are unable to differentiate towards monocytes when treated with 12-0-tetradecanoylphorbol-13-acetate (TPA) (Bunce et al, 1983)
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