Biosynthesis of ferritin subunits from different cell lines of HL-60 human promyelocytic leukaemia cells and the release of acidic isoferritin-inhibitory activity against normal granulocyte-macrophage progenitor cells

Purification and characterization of a human leukemia cell-derived immunosuppressive factor

A human leukemia cell-derived suppressor factor (LDSF) capable of suppressing in vitro proliferation and activation of normal human lymphocytes was purified from human leukemic HL-60 cells. LDSF is constitutively produced by the cells and was purified from serum free culture supernatant by a combination of ion-exchange chromatography, gel filtration and electrophoresis. Purified LDSF was determined to be a single chain protein with an apparent molecular mass of 66,000 daltons. LDSF was not cytolytic to lymphocytes, was heat stable at 70 degrees C, and did not have any effect on IL-2 or transferrin receptor expression.

Model for intermediate steps in monocytic differentiation: c-myc, c-fms, and ferritin as markers

A mature hematopoietic cell represents the end product of a stepwise differentiation process. As a model system for studying differentiation, the human promyelocytic leukemia cell line HL-60 undergoes terminal monocytic/macrophagic differentiation following exposure to either phorbol 12-myristate 13-acetate or 1,25-dihydroxyvitamin D3. We have derived and analyzed a variant HL-60 cell line, 1F10, that permits the study of several intermediate steps in the myeloid differentiation process. These intermediate steps are documented by cell cycle data and phenotype analysis as well as markers such as c-myc, c-fms, and both subunits of ferritin.

Changes in cellular ferritin content during myeloid differentiation of human leukemic cell lines

The human promyelocytic cell lines HL-60 can be induced to undergo differentiation to either granulocyte- or macrophage-like cells. We followed the changes in the synthesis and content of ferritin in this and other cell lines during differentiation. Ferritin content of HL-60 cells ranged from 11 to 81 fg/cell, depending on the clone tested. Following exposure to dimethylsulfoxide (DMSO) or retinoic acid (RA) an increase in ferritin and a decrease in total protein synthesis was observed, resulting in increased ferritin content, reaching a peak after 2 days. This increase occurred prior to the appearance of the typical morphological and functional characteristics of mature granulocytes. A correlation was found between concentrations of DMSO effective in inducing differentiation and the increase in ferritin content. Other inducers of granulocyte differentiation had a similar effect, while 12-O-tetradecanoylphorbol-13-acetate (TPA), an inducer of macrophage differentiation, had not. Another human cell line (U-937), which was induced into monocyte-like cells by RA, showed a twofold increase in ferritin content following differentiation. Addition of iron to the culture medium increased ferritin content of both differentiating and non-differentiating cells, but the former responded to lower concentrations of iron. The increase in ferritin during differentiation, however, was not related to an accelerated iron uptake. The present results suggest that changes in the intracellular ferritin of the developing myeloid cells may play a regulating role in the process of maturation of these cells.

Biochemical and immunological characteristics of ferritin from HL-60, U-937 and K-562 cell lines: Implications for haemopoietic regulation

It has been suggested that acidic isoferritins play a major role in the regulation of human granulocyte-macrophage (CFU-GM) proliferation. Such regulatory isoferritins are said to occur in some human tissues including both leukaemic and normal leucocytes, and certain established cell lines. They are glycosylated and bind to Con A. Extracts from HL-60, U-937 and K-562 cell lines are said to contain inhibitory activity but only in HL60 cells is the activity neutralized by antibody to acidic isoferritins. The properties of ferritin from these cell lines have been investigated. HL60 and U-937 extracts contained predominantly basic (spleen-type) isoferritins and K-562 extracts predominantly acidic (heart-type) isoferritins on immunoradiometric assay. None of the ferritin bound to Con A. On anion exchange chromatography ferritin from U-937 was basic in character, that from K-562 was acidic and HL-60 contained a variety of isoferritins. The identification of glycosylated acidic isoferritins as inhibitors of granulopoiesis appears to be an oversimplification and the classification of isoferritins on the basis of two subunit types may also need revision.