ABSTRACT
Three variants of the human monoblastic cell line U937 with different degrees of sensitivity to the antiproliferative action of interferon-alpha (IFN-alpha were examined for phenotypic differences. The highly IFN-sensitive variant U937-V expressed twice as many IFN-alpha binding sites as both its IFN-alpha-resistant derivative U937-VR and the cell line U937 exhibiting a 20-fold reduction in IFN-alpha sensitivity as compared to U937-V cells. All three variants were IFN-reactive with regard to induction of 2',5'-oligoadenylate (2-5A) synthetase activity and were similarly sensitive to the growth-inhibiting action of IFN-gamma and tumor necrosis factor. Responsiveness to the antiproliferative effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), however, was confined to cell lines U937 and U937-VR. Although expressing a comparable number of GM-CSF receptors, the highly IFN-sensitive variant U937-V was refractory to GM-CSF. Flow cytometry revealed a marked difference in the expression of the antigen CD11b which was detectable on 85% of cells of the U937-V line but only on approximately 25% of cells derived from the U937 and U937-VR lines. Results thus demonstrate opposite sensitivity of U937 cells to the growth-inhibiting action of IFN-alpha and GM-CSF, apparently dependent on the state of U937 differentiation as determined by expression of the CD11b antigen.
Subject(s)
Granulocyte-Macrophage Colony-Stimulating Factor/therapeutic use , Interferon-alpha/therapeutic use , Leukemia, Monocytic, Acute/drug therapy , 2',5'-Oligoadenylate Synthetase/biosynthesis , 2',5'-Oligoadenylate Synthetase/metabolism , Cell Differentiation/drug effects , Cell Division/drug effects , Enzyme Induction/drug effects , Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology , Humans , Infant, Newborn , Interferon-alpha/metabolism , Interferon-alpha/pharmacology , Interferon-gamma/pharmacology , Phenotype , Protein Binding , Receptors, Interferon/metabolism , Sensitivity and Specificity , Tumor Cells, Cultured , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
Activity of the interferon-induced enzyme 2'-5' oligoadenylate synthetase (2-5 OAS) was measured in peripheral blood mononuclear cells (PBMCs) and serum of patients with chronic phase Ph'-positive chronic myelogenous leukemia (CML) treated with interferon-alpha (IFN-alpha) (4 x 10(6) IU/m2) alone or in combination with 50 micrograms IFN-gamma. At the beginning of IFN therapy, marked elevation of 2-5 OAS titers was detected in PBMCs (pretreatment 0.03-1.62, median 0.2; during treatment 0.8-13.14, median 4.31; 22 patients studied) and in serum (pretreatment 21-156 pmol/dl, median 62; during treatment 532-1740 pmol/dl, median 800; eight patients studied). However, 2-5 OAS titers were not related to clinical outcome or IFN therapy and also during IFN resistance elevated 2-5 OAS activity in PBMCs (median 3.45; range 1.05-13.14; 11 patients studied) were detected. These data argue against direct involvement of the 2-5 OAS system in the therapeutic effect of IFN in CML. However, 2-5 OAS titers in PBMCs or serum appear to be a reliable control of biologically active IFN therapy.
