Extensive crosslinking of CD22 by epratuzumab triggers BCR signaling and caspase-dependent apoptosis in human lymphoma cells.
MAbs
; 7(1): 199-211, 2015.
Article
en En
| MEDLINE
| ID: mdl-25484043
ABSTRACT
Epratuzumab has demonstrated therapeutic activity in patients with non-Hodgkin lymphoma, acute lymphoblastic leukemia, systemic lupus erythematosus, and Sjögren's syndrome, but its mechanism of affecting normal and malignant B cells remains incompletely understood. We reported previously that epratuzumab displayed in vitro cytotoxicity to CD22-expressing Burkitt lymphoma cell lines (Daudi and Ramos) only when immobilized on plates or combined with a crosslinking antibody plus a suboptimal amount of anti-IgM (1 µg/mL). Herein, we show that, in the absence of additional anti-IgM ligation, extensive crosslinking of CD22 by plate-immobilized epratuzumab induced intracellular changes in Daudi cells similar to ligating B-cell antigen receptor with a sufficiently high amount of anti-IgM (10 µg/mL). Specifically, either treatment led to phosphorylation of CD22, CD79a and CD79b, along with their translocation to lipid rafts, both of which were essential for effecting caspase-dependent apoptosis. Moreover, such immobilization induced stabilization of F-actin, phosphorylation of Lyn, ERKs and JNKs, generation of reactive oxygen species (ROS), decrease in mitochondria membrane potential (Δψm), upregulation of pro-apoptotic Bax, and downregulation of anti-apoptotic Bcl-xl and Mcl-1. The physiological relevance of immobilized epratuzumab was implicated by noting that several of its in vitro effects, including apoptosis, drop in Δψm, and generation of ROS, could be observed with soluble epratuzumab in Daudi cells co-cultivated with human umbilical vein endothelial cells. These results suggest that the in vivo mechanism of non-ligand-blocking epratuzumab may, in part, involve the unmasking of CD22 to facilitate the trans-interaction of B cells with vascular endothelium.
Palabras clave
488-annexin V, Alexa Fluor 488-conjugated annexin V; 7-AAD, 7-aminoactinomycin D, Syk, spleen tyrosine kinase; Anti-IgM, F(ab')2 fragment of affinity-purified goat anti-human IgM, Fc5µ fragment; BCR; BCR, B-cell antigen receptor; BSA, bovine serum albumin; CD22; CM-H2DCF-DA, 2',7'-dichlorodihydrofluorescein diacetate; DNP, 2,4-dinitrophenyl; EC, endothelial cells; ERKs, extracellular signal-regulated kinases; FBS, fetal bovine serum; FITC-DNase I, fluorescein isothiocyanate-conjugated DNase I; GAH, F(ab')2 fragment of affinity-purified goat anti-human IgG Fcγ fragment-specific; HUV-EC; HUV-EC, human umbilical vein endothelial cells; ITIM, immunoreceptor tyrosine-based inhibition motif; JNKs, c-Jun N-terminal kinases; JP, jasplakinolide; LatB, latrunculin B; Lyn, Lck/Yes novel tyrosine kinase; MAP kinases, mitogen-activated protein kinases; MTS, (3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium; PARP, poly(ADP-ribose) polymerase; PBS, phosphate-buffered saline; PLCγ2, phospholipase C, isotype gamma 2; ROS, reactive oxygen species; Rhodamine-anti-IgG, rhodamine-conjugated F(ab')2 fragment of affinity-purified goat anti-human IgG, F(ab')2 fragment-specific; TMRE/tetramethylrhodamine/ethyl ester; epratuzumab; human B-cell lymphoma; immobilized; mIgM, membrane IgM; Δψm, mitochondria membrane potential
Texto completo:
1
Colección:
01-internacional
Asunto principal:
Receptores de Antígenos de Linfocitos B
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Transducción de Señal
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Linfoma de Burkitt
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Apoptosis
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Caspasas
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Lectina 2 Similar a Ig de Unión al Ácido Siálico
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Anticuerpos Monoclonales Humanizados
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Recubrimiento Inmunológico
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Proteínas de Neoplasias
Límite:
Humans
Idioma:
En
Revista:
MAbs
Asunto de la revista:
ALERGIA E IMUNOLOGIA
Año:
2015
Tipo del documento:
Article