title: Endoplasmic reticulum stress-mediated apoptosis of EBV-transformed B cells by cross-linking of CD70 is dependent upon generation of reactive oxygen species and activation of p38 MAPK and JNK pathway.
abstract: CD70 is expressed in normal activated immune cells as well as in several types of tumors. It has been established that anti-CD70 mAb induces complement-dependent death of CD70(+) tumor cells, but how anti-CD70 mAb affects the intrinsic signaling is poorly defined. In this report, we show that ligation of CD70 expressed on EBV-transformed B cells using anti-CD70 mAb induced production of reactive oxygen species (ROS) and subsequent apoptosis. We observed an early expression of endoplasmic reticulum (ER) stress response genes that preceded the release of apoptotic molecules from the mitochondria and the cleavage of caspases. CD70-induced apoptosis was inhibited by pretreatment with the ER stress inhibitor salubrinal, ROS quencher N-acetylcysteine, and Ca(2+) chelator BAPTA. We supposed that ROS generation might be the first event of CD70-induced apoptosis because N-acetylcysteine blocked increases of ROS and Ca(2+), but BAPTA did not block ROS generation. We also found that CD70 stimulation activated JNK and p38 MAPK. JNK inhibitor SP600125 and p38 inhibitor SB203580 effectively blocked upregulation of ER stress-related genes and cleavage of caspases. Inhibition of ROS generation completely blocked phosphorylation of JNK and p38 MAPK and induction of ER stress-related genes. Taken together, we concluded that cross-linking of CD70 on EBV-transformed B cells triggered ER stress-mediated apoptosis via ROS generation and JNK and p38 MAPK pathway activation. Our report reveals alternate mechanisms of direct apoptosis through CD70 signaling and provides data supporting CD70 as a viable target for an Ab-based therapy against EBV-related tumors.
authors.affiliation: Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan, Korea.
authors.forename: Ga Bin
authors.initials: GB
authors.lastname: Park
authors.forename: Yeong Seok
authors.initials: YS
authors.lastname: Kim
authors.forename: Hyun-Kyung
authors.initials: HK
authors.lastname: Lee
authors.forename: Hyunkeun
authors.initials: H
authors.lastname: Song
authors.forename: Dae-Ho
authors.initials: DH
authors.lastname: Cho
authors.forename: Wang Jae
authors.initials: WJ
authors.lastname: Lee
authors.forename: Dae Young
authors.initials: DY
authors.lastname: Hur
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D053282:CD27 Ligand / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D002144:Callithrix; D002461:Cell Line, Transformed; D002614:Chelating Agents; D002934:Cinnamates / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000276:immunology* / Q000378:metabolism; D020031:Epstein-Barr Virus Infections / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D004854:Herpesvirus 4, Human / Q000276:immunology* / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000276:immunology; D017382:Reactive Oxygen Species / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects / Q000276:immunology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism
chemical_list: D000873:Anthracenes; D000911:Antibodies, Monoclonal; D053282:CD27 Ligand; D002614:Chelating Agents; D002934:Cinnamates; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; C496827:salubrinal; C432165:pyrazolanthrone; D004533:Egtazic Acid; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D013890:Thiourea; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000111:Acetylcysteine