title: CM1 ligation initiates apoptosis in a caspase 8-dependent manner in Ramos cells and in a mitochondria-controlled manner in Raji cells.
abstract: Burkitt lymphoma (BL) is a tumor with the characteristics of germinal center B cells. We previously reported that the CM1 (centrocyte/-blast marker 1) molecule is expressed only in germinal center B cells, specifically, in a subpopulation of centroblasts and centrocytes. In the present study, we investigated the apoptosis induced by anti-CM1 in the Ramos and Raji human BL cell lines. The Ramos is protected from apoptosis by the crosslinking of sIgM and the calcium ionophore by the ligation of CD40 with anti-CD40 monoclonal antibodies (mAb) or soluble CD40 ligand (sCD40L). In this investigation on the effect of CM1 on apoptosis in BL cell lines, we found that cellular signaling by CM1 induces apoptosis and decreases cell viability, in BL cell lines cultured for 24 hours with protein-G agarose beads conjugated anti-CM1 mAb. Stimulation by CD40 ligated with sCD40L protected Raji cells from CM1-induced apoptosis, but did not protect Ramos cells. Furthermore, after anti-CM1 mAb stimulation, CD95 expression was upregulated and CD40 expression was unaltered or slightly decreased in Ramos cells, whereas CD95 was downregulated and CD40 was slightly upregulated in Raji cells. The engagement of CD40 by sCD40L enhanced CD95 expression, but the level of CM1 expression was unchanged in Ramos. However, sCD40L downregulated both CD95 and CM1 expression in Raji. In addition, the caspase-8 specific inhibitor blocked CM1-induced apoptosis in Ramos cells, but not in Raji cells. Increased mitochondrial membrane permeabilization was observed only in Raji cells. Moreover, the effector caspase inhibitor, z-DEVD, blocked CM1-mediated apoptosis in both cell lines. We found that CM1-induced apoptosis is achieved via different initiation pathways, which are cell-type dependent.
authors.affiliation: Department of Anatomy, Seoul National University, College of Medicine and Institute of Allergy and Clinical Immunology, Medical Research Center, Seoul National University, Seoul, South Korea.
authors.forename: Daejin
authors.initials: D
authors.lastname: Kim
authors.forename: Dae Young
authors.initials: DY
authors.lastname: Hur
authors.forename: Yeong Seok
authors.initials: YS
authors.lastname: Kim
authors.forename: Kyungmi
authors.initials: K
authors.lastname: Lee
authors.forename: Youngseon
authors.initials: Y
authors.lastname: Lee
authors.forename: Daeho
authors.initials: D
authors.lastname: Cho
authors.forename: Jae Seung
authors.initials: JS
authors.lastname: Kang
authors.forename: Young-in
authors.initials: YI
authors.lastname: Kim
authors.forename: Eunsil
authors.initials: E
authors.lastname: Hahm
authors.forename: Yoolhee
authors.initials: Y
authors.lastname: Yang
authors.forename: Suyoung
authors.initials: S
authors.lastname: Yoon
authors.forename: Seonghan
authors.initials: S
authors.lastname: Kim
authors.forename: Won Bok
authors.initials: WB
authors.lastname: Lee
authors.forename: Hae Young
authors.initials: HY
authors.lastname: Park
authors.forename: Yoon Berm
authors.initials: YB
authors.lastname: Kim
authors.forename: Young-il
authors.initials: YI
authors.lastname: Hwang
authors.forename: Ka Y
authors.initials: KY
authors.lastname: Chang
authors.forename: Wang Jae
authors.initials: WJ
authors.lastname: Lee
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000032:analysis; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D018951:Antigens, CD20 / Q000032:analysis; D000954:Antigens, Surface / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology; D023201:CD40 Ligand / Q000276:immunology; D000071178:CD48 Antigen; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000276:immunology*; D006801:Humans; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008928:Mitochondria / Q000276:immunology*; D015260:Neprilysin / Q000032:analysis; D014066:Palatine Tonsil / Q000166:cytology; D014281:Trihexosylceramides / Q000032:analysis; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000276:immunology
chemical_list: D015703:Antigens, CD; D018951:Antigens, CD20; D000954:Antigens, Surface; D019013:CD40 Antigens; D000071178:CD48 Antigen; D008562:Membrane Glycoproteins; D014281:Trihexosylceramides; D019014:fas Receptor; D023201:CD40 Ligand; C018549:globotriaosylceramide; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D051997:ADP-ribosyl Cyclase 1; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D015260:Neprilysin