Mechanism of apoptosis induced by IFN-alpha in human myeloma cells: role of Jak1 and Bim and potentiation by rapamycin.
Interferon-alpha (IFN-alpha) has been used for the last 20 years in the maintenance therapy of multiple myeloma (MM), though it is only effective in some patients. Congruent with this, IFN-alpha induces apoptosis in some MM cell lines. Understanding the mechanism of IFN-alpha-induced apoptosis could be useful in establishing criteria of eligibility for therapy. Here we show that IFN-alpha-induced apoptosis in the MM cell lines U266 and H929 was completely blocked by a specific inhibitor of Jak1. The mTOR inhibitor rapamycin mitigated apoptosis in U266 but potentiated it in H929 cells. IFN-alpha induced PS exposure, DeltaPsi(m) loss and pro-apoptotic conformational changes of Bak, but not of Bax, and was fully prevented by Mcl-1 overexpression in U266 cells. IFN-alpha treatment caused the release of cytochrome c from mitochondria to cytosol and consequently, a limited proteolytic processing of caspases. Apoptosis induced by IFN-alpha was only slightly prevented by caspase inhibitors. Levels of the BH3-only proteins PUMA and Bim increased during IFN-alpha treatment. Bim increase and apoptosis was prevented by transfection with the siRNA for Bim. PUMA-siRNA transfection reduced electroporation-induced apoptosis but had no effect on apoptosis triggered by IFN-alpha. The potentiating effect of rapamycin on apoptosis in H929 cells was associated to an increase in basal and IFN-alpha-induced Bim levels. Our results indicate that IFN-alpha causes apoptosis in myeloma cells through a moderate triggering of the mitochondrial route initiated by Bim and that mTOR inhibitors may be useful in IFN-alpha maintenance therapy of certain MM patients.
Gómez-Benito
Maria
M
Departamento de Bioquimica, Biologia Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain.
Balsas
Patricia
P
Carvajal-Vergara
Xonia
X
Pandiella
Atanasio
A
Anel
Alberto
A
Marzo
Isabel
I
Naval
Javier
J
D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D053613:Janus Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009101:Multiple Myeloma / Q000201:enzymology / Q000473:pathology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology*
D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D016898:Interferon-alpha; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D045304:Cytochromes c; D053613:Janus Kinase 1; D020169:Caspases; D005978:Glutathione; D020123:Sirolimus