Differential human multiple myeloma cell line responsiveness to interferon-alpha. Analysis of transcription factor activation and interleukin 6 receptor expression.
Although IFN-alpha is commonly used as maintenance treatment for multiple myeloma patients, its effectiveness is varied. In this study, we have used a panel of IL-6 responsive myeloma cell lines that vary remarkably in responsiveness to IFN-alpha. Three cell lines were growth arrested by IFN-alpha; however, IFN-alpha significantly stimulated growth of the fourth cell line, KAS-6/1. Our studies have focused on elucidating the mechanism of differential IFN-alpha responsiveness. First, we have shown that IFN-alpha-stimulated growth of the KAS-6/1 cells did not result from induction of autocrine IL-6 expression. Second, analysis of Stats 1, 2, and 3 and IFN regulatory factor-1 (IRF-1) and IRF-2 activation failed to reveal differences between the IFN-alpha growth-arrested or growth-stimulated cells. Third, although IFN-alpha treatment of the IFN-alpha growth-inhibited cell lines reduced IL-6 receptor (IL-6R) expression, IFN-alpha also reduced KAS-6/1 IL-6R expression. Finally, although IFN-alpha treatment reduced IL-6R numbers on each cell line, analysis of Stat protein activation revealed that the receptors were still functional. We conclude that myeloma cell responsiveness to IFN-alpha is heterogeneous and that mechanisms of IFN-alpha-mediated growth inhibition other than IL-6R downregulation must exist in myeloma. Identification of these mechanisms may allow development of agents that are more universally effective than IFN-alpha.
Jelinek
D F
DF
Department of Immunology, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA. jelinek.diane@mayo.edu
Aagaard-Tillery
K M
KM
Arendt
B K
BK
Arora
T
T
Tschumper
R C
RC
Westendorf
J J
JJ
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000032:analysis; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015151:Immunoblotting; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis / Q000502:physiology; D009101:Multiple Myeloma / Q000188:drug therapy / Q000276:immunology*; D009500:Neutralization Tests; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D011233:Precipitin Tests; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis / Q000502:physiology; D012097:Repressor Proteins; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000032:analysis; D014157:Transcription Factors
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; C494229:IRF2 protein, human; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D016898:Interferon-alpha; D015850:Interleukin-6; D010750:Phosphoproteins; D015375:Receptors, Interleukin-2; D012097:Repressor Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D007371:Interferon-gamma; D004247:DNA