Loss of promyelocytic maturation in HL60 sublines: a potential model for leukaemia progression

Summary. The majority of cells of the human leukaemic line HL60 appear to be promyelocytes which can be stimulated to mature into functioning neutrophils. We report here the derivation of stable subclones from the parent line which differ. Two forms of variant were obtained: (1) those with a defined lesion, selected by resistance to kill by 6-thioguanine, which matured in the presence of DMSO and retinoic acid but not in hypoxanthine. They also continued to express peroxidase and a major granulocyte antigen, and (2) those obtained by clonal growth in DMSO which did not mature in the presence of any compound tested including hypoxanthine, DMSO, retinoic acid and actinomycin D and lacked granules, peroxidase and the granulocyte antigen. The concurrent loss of the characteristic of maturability and the phenotype of myeloid commitment suggests that the control of the two phenomena may be related. These variant cell lines provide a useful model in which to study how human leukaemic cells may become arrested in less differentiated stages of development.