Characterization of interleukin-10 receptor expression on B-cell chronic lymphocytic leukemia cells.
B-cell chronic lymphocytic leukemia (B-CLL) cells accumulate in vivo in the G0/G1 phase of the cell cycle, suggesting that their malignant expansion is due, at least in part, to a delay in cell death. However, the cellular or molecular factors responsible for a delay in B-CLL cell death are unknown. B-CLL cells do express receptors for interferon-alpha (IFN-alpha) and IFN-gamma, and activation of both has been shown to promote B-CLL survival in vitro by preventing apoptosis. The interleukin-10 (IL-10) receptor is another member of the IFN receptor family, but its ligand, IL-10, has been reported to induce apoptosis in B-CLL cells. In the current study, we undertook a biochemical analysis of IL-10 receptor expression on freshly isolated B-CLL cells and characterized the functional responsiveness of IL-10 binding to its constitutively expressed receptor. We show that B-CLL cells bind IL-10 with significant specificity and express between 47 and 127 IL-10 receptor sites per cell, with a dissociation constant in the range of 168 to 426 x 10(-12) mol/L. Ligand binding and activation of the IL-10 receptor expressed on B-CLL cells results in the phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT3 proteins. This pattern of STAT protein phosphorylation is identical to IL-10 receptor activation on normal cells and similar to IFN-alpha (STAT1 and STAT3) and IFN-gamma (STAT1) receptor activation in CLL. Further, in consecutive samples of fresh blood obtained from patients with B-CLL cells, the addition of IL-10 inhibited B-CLL proliferation, enhanced B-CLL differentiation, but did not induce apoptosis. Indeed, IL-10, like IFN-gamma, was able to significantly reduce the amount of B-CLL cell death caused by hydrocortisone-induced apoptosis. We conclude that cytokines, which signal through the interferon family of receptors, have comparable functional effects on B-CLL cells.
Jurlander
J
J
Department of Molecular and Cell Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Lai
C F
CF
Tan
J
J
Chou
C C
CC
Geisler
C H
CH
Schriber
J
J
Blumenson
L E
LE
Narula
S K
SK
Baumann
H
H
Caligiuri
M A
MA
D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism; D006801:Humans; D016753:Interleukin-10 / Q000276:immunology / Q000378:metabolism; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology* / Q000378:metabolism; D018123:Receptors, Interleukin / Q000096:biosynthesis* / Q000276:immunology; D053701:Receptors, Interleukin-10; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000276:immunology*; D015534:Trans-Activators / Q000276:immunology / Q000378:metabolism
D004268:DNA-Binding Proteins; D018123:Receptors, Interleukin; D053701:Receptors, Interleukin-10; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D016753:Interleukin-10