Continuous growth and differentiation of human myeloid leukaemic cells in suspension culture

Abstract

ATTEMPTS to develop long-term suspension cultures of human myeloid leukaemic cells have met with limited success. Lymphoblastoid lines carrying the Epstein–Barr virus genome occasionally arise during such attempts but these lymphoid cells originate from contaminating B lymphocytes and not from the leukaemic myeloid cells¹. A line established from the pleural fluid of a patient with chronic myeloid leukaemia in blast crisis² (designated K-562) has no B-cell or T-cell markers^3–4 and does not seem to be of lymphoid origin⁴. Its lack of morphological and histochemical differentiation^2–4, however, makes it difficult to determine whether these cells are derived from myeloblasts or more primitive stem cells⁴. Another less documented cell line (8261) derived from the peripheral blood of a patient with acute myelogenous leukaemia showed apparent morphological and functional differentiation in agar in the presence of a feeder layer of peripheral blood leukocytes but did not differentiate in suspension culture⁵. Our laboratory previously reported that cultures of differentiating myeloid leukaemic cells can be maintained for several months in suspension culture but only when enriched with conditioned media (CM) from certain monolayer fibroblastic cultures of first trimester whole human embryos (ref. 6 and Ruscetti et al. in preparation). We describe here for the first time the derivation from myeloid leukaemic cells of a leukocyte culture that by morphological and histochemical criteria clearly and persistently differentiates along the myeloid series without an exogenous source of conditioned medium.