Abstract
Abstract
The K-562 leukemia cell line, originally established in our laboratory, has been characterized as an early precursor of the granulocytic series with a block for differentiation. Since K-562 blasts did not differentiate when cultured for 7-8 days in liquid media or 14-16 days in agar-gel an attempt was made to stimulate their potential for spontaneous differentiation by prolonging the time in culture. Inducers of differentiation were not added to the cultures and the cells were studied when they reached the steady state rather than during exponential growth. The cultivation of K-562 cells for 10 to 11 days in media gradually depleted of the essential nutrients needed for cell division induced their differentiation into early precursors of the monocytic, granulocytic, and erythrocytic series. Thus, the peroxidase reaction for hemoglobin demonstrates benzidine-positive material limited to the region of the Golgi apparatus. Analysis of the hemoglobin by isoelectric focusing indicated major bands in the region of embryonic hemoglobin. Most cells (80-90%) give a strong reaction for α-naphthyl acetate esterase typical of monocytes and as many as 30 to 40% of the cells have abundant red cytoplasmic granules of naphthol AS-D chloroacetate esterase characteristic of granulocytic precursors. Myeloperoxidase activity was found in 5 to 10% of the cells. Polyploid cells (5-8%) and early myelomonocytic precursors have PAS-positive material, were stained with Sudan black, and possessed abundant acid phosphatase. The data support the conclusion that K-562 is, indeed, a multipotential leukemia cell line of human origin.
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