Human Lymphoma Cell Line U937 Research Articles

Differentiated HL-60 promyelocytic leukaemia cells produce a factor inducing differentiation

The bipotential human promyelocytic leukaemia cell line HL-60 can be induced to differentiate into monocytic or granulocytic cells by treatment with 1,25 dihydroxyvitamin D 3 (1,25(OH) 2D 3) or dimethylsulphoxide (DMSO) respectively. Conditioned media (CM) from 1,25(OH) 2D 3- or DMSO-treated cells were able to induce monocytic differentiation in fresh HL-60 cells as measured by induction of non-specific esterase and macrophage surface markers. CM from 1,25(OH) 2D 3-treated cells also led to a dose dependent loss of proliferative capacity in soft agar colony assays. These effects were not due to a toxic effect of the CM or to residual inducer present in the CM. γ-interferon and GM-CSF were apparently not responsible for these effects. CM from the human histocytic lymphoma cell line U937 led to only a low level of induction of macrophage differentiation in fresh HL-60 cells. The defect in HL-60 leukaemic cells may therefore be at the level of induction of an autonomously-produced differentiation factor.

Structure-activity relationships of aromatic retinoids on the differentiation of the human histiocytic lymphoma cell line U-937

The differentiation-inducer activity of a series of derivatives modified on the terminal ring, the polyene side-chain or the polar end group of the retinoic acid molecule was tested on the human histiocytic lymphoma cell line U-937 and compared with that of all- trans-retinoic acid. Only retinoids with both an unsaturated terminal end ring and a free carboxyl polar end group were found to be active in this system. Introduction of an aromatic ring in place of the first double bond of the side chain increased highly the activity whereas cyclisation of the last two double bonds decreased it. Replacement of the unsaturated terminal ring by an aromatic ring abolished the activity as did the esterification of the carboxyl end group or its replacement by a sodium sulfinate, sodium sulfonate or ethyl sulfone end group. All but only the active retinoids induced the same morphological and biochemical changes on U-937 cells, suggesting that they have the same route of action. However, biologically inactive retinoids were shown to be able to inhibit the differentiation of U-937 cells, induced by active ones, indicating that they can compete for a common “receptor”.

Evidence for a gamma-interferon receptor that regulates macrophage tumoricidal activity.

Gamma-interferon (IFN-gamma) is the macrophage-activating factor (MAF) produced by normal murine splenic cells and the murine T cell hybridoma 24/G1 that induces nonspecific tumoricidal activity in macrophages. Incubation of 24/G1 supernatants diluted to 8.3 IRU IFN-gamma/ml with 6 X 10(6) elicited peritoneal macrophages or bone marrow-derived macrophages for 4 h at 37 degrees C, resulted in removal of 80% of the MAF activity from the lymphokine preparation. Loss of activity appeared to result from absorption and not consumption because (a) 40% of the activity was removed after exposure to macrophage for 30 min at 4 degrees C, (b) no reduction of MAF activity was detected when the 24/G1 supernatant was incubated with macrophage culture supernatants, and (c) macrophage-treated supernatants showed a selective loss of MAF activity but not interleukin 2 (IL-2) activity. Absorption was dependent on the input of either IFN-gamma or macrophages and was time dependent at 37 degrees C but not at 4 degrees C. With four rodent species tested, absorption of murine IFN-gamma displayed species specificity. However, cultured human peripheral blood monocytes and the human histiocytic lymphoma cell line U937 were able to absorb the murine lymphokine. Although the majority of murine cell lines tested absorbed 24/G1 MAF activity, two murine macrophage cell lines, P388D1 and J774, were identified which absorbed significantly reduced amounts of natural IFN-gamma. Purified murine recombinant IFN-gamma was absorbed by elicited macrophages but not by P388D1. Normal macrophages but not P388D1 bound fluoresceinated microspheres coated with recombinant IFN-gamma and binding was inhibited by pretreatment of the normal cells with 24/G1 supernatants. Scatchard plot analysis showed that 12,000 molecules of soluble 125I-recombinant IFN-gamma bound per bone marrow macrophage with a Ka of 0.9 X 10(8) M-1. Binding was quantitatively inhibitable by natural IFN-gamma but not by murine IFN alpha. IFN-beta competed only weakly. Monoclonal antibodies against IFN-gamma either inhibited or enhanced MAF activity by blocking or increasing IFN-gamma binding to macrophages, respectively. These results indicate that IFN-gamma reacts with a receptor on macrophage in a specific and saturable manner and this interaction initiates macrophage activation.

Binding of 125I-insulin to the human histiocytic lymphoma cell line U-937: Effect of differentiation with retinoic acid

The human histiocytic lymphoma line U-937 consists of cells having characters of immature monocytes. We have demonstrated that these cells posses highly specific insulin receptors with binding properties similar to that found for mature human blood monocytes. 125I-insulin binding increased progressively with time to reach a maximum at 90 min at 22°C and was proportional to the number of cells in the incubation medium. Insulin degradation as assessed by TCA precipitation was negligible. Scatchard analysis of the binding data was curvilinear and the total number of insulin binding sites was around 13,500. The average affinity profile gave an ‘unoccupied site’ affinity constant of 1.34 nM −1. When the U-937 cells were induced to differentiate into morphologically and functionally monocyte-like cells, after incubation with retinoic acid, the total number of binding sites decreased significantly with no change in the affinity of the hormone for its receptor.

Accessory function of human tumor cell lines. I. Production of interleukin 1 by the human histiocytic lymphoma cell line U-937.

The established human histiocytic lymphoma cell line U-937 spontaneously produced a factor with biological activity similar to that ascribed to interleukin 1 (IL 1). Actually, supernatants from U-937 cells promoted proliferation of thymocytes initiated by concanavalin A (Con A) and replaced the requirement of accessory cells for activation of highly purified circulating T lymphocytes induced by Con A. Phorbol myristate acetate (PMA) significantly increased the titers of the helper factor produced by U-937 cells as compared to that secreted by non-PMA-treated U-937 cells or PMA-stimulated P388D1 murine macrophage tumor cells. Generally U-937 cells did not secrete detectable IL 1 activity during the first 24-48 h of culture. However, after this initial period the level of IL 1 activity increased and reached a maximum at 5-6 days of culture. Finally, the helper factor released by U-937 cells had an apparent mol. wt. of 12000-15000 as determined by Sephadex G-100 chromatography and lacked interleukin 2 activity as shown by its inability to support growth of IL 2-addicted T cell lines. To our knowledge this is the first report of an established human cell line capable of producing IL 1.

Preparation and characterization of lymphocyte-activating factor (LAF) from acute monocytic and myelomonocytic leukemia cells

Leukemia cells from acute monocytic and myelomonocytic patients undergoing leukophoresis have been used to prepare large quantities of lymphocyte-activating factor (LAF). The chemical properties of normal leukocyte LAF and leukemia cell LAF from a single donor for industrial-scale purification. The human histiocytic lymphoma cell line U937 was also evaluated as a possible source of LAF. Although exhibiting several monocyte-specific properties, the U937 cell line failed to release LAF.