Development of capping ability during differentiation of HL‐60 human promyelocytic leukemia cells

Developmental changes in cell surface and cytoskeletal elements have been studied in human promyelocytic leukemia cells (line HL‐60) which differentiate into functionally mature myeloid cells when grown in dimethyl sulfoxide (DMSO)‐supplemented medium. Both differentiated and undifferentiated HL‐60 cells bind fluorescent concanavalin A (F‐Con A) in a diffuse pattern over the entire cell surface. As with normal neutrophils, pretreatment of the differentiated HL‐60 cells with colchicine before incubation with Con A causes the formation of large cytoplasmic protrusions over which the lectin associates into a cap. On the other hand, similarly treated undifferentiated HL‐60 cells do not form the cytoplasmic protuberances and are unable to cap the Con A. Transmission electron microscopy reveals that the number and distribution of microtubules and microfilaments change during differentiation. Thus, developing myeloid cells undergo important alterations in the structure and function of the cytoskeleton as they differentiate into mature phagocytes.