K562 human leukaemic cells synthesise embryonic haemoglobin in response to haemin

STUDIES of the regulation of human erythropoiesis and haemoglobin synthesis at different phases of development are hampered by the lack of a self-sustaining culture in which erythroid differentiation can be examined, and by difficulties in obtaining erythropoietic tissue in embryonic and early fetal life1. New insights into the regulation of murine erythropoiesis have been obtained by the study of established cultures of erythro-leukaemic cells (Friend cells) which can be induced to differentiate in vitro2. Recently, Andersson et al. 3,4 have reported that the K562 human cell line, obtained from a patient with an acute transformation of chronic myeloid leukaemia (CML) has properties in common with erythroid cells. In particular, cells of this line contain glycophorin and spectrin in their membranes and synthesise minute amounts of haemoglobin, detectable by radioimmunoassay. We have investigated the capacity of these cells to differentiate in vitro and report here that they are induced by haemin to synthesise large amounts of haemoglobin; preliminary analysis indicates that this is predominantly of the embryonic type.