title: A single-chain Fv diabody against human leukocyte antigen-A molecules specifically induces myeloma cell death in the bone marrow environment.
abstract: Cross-linked human leukocyte antigen (HLA) class I molecules have been shown to mediate cell death in neoplastic lymphoid cells. However, clinical application of an anti-HLA class I antibody is limited by possible side effects due to widespread expression of HLA class I molecules in normal tissues. To reduce the unwanted Fc-mediated functions of the therapeutic antibody, we have developed a recombinant single-chain Fv diabody (2D7-DB) specific to the alpha2 domain of HLA-A. Here, we show that 2D7-DB specifically induces multiple myeloma cell death in the bone marrow environment. Both multiple myeloma cell lines and primary multiple myeloma cells expressed HLA-A at higher levels than normal myeloid cells, lymphocytes, or hematopoietic stem cells. 2D7-DB rapidly induced Rho activation and robust actin aggregation that led to caspase-independent death in multiple myeloma cells. This cell death was completely blocked by Rho GTPase inhibitors, suggesting that Rho-induced actin aggregation is crucial for mediating multiple myeloma cell death. Conversely, 2D7-DB neither triggered Rho-mediated actin aggregation nor induced cell death in normal bone marrow cells despite the expression of HLA-A. Treatment with IFNs, melphalan, or bortezomib enhanced multiple myeloma cell death induced by 2D7-DB. Furthermore, administration of 2D7-DB resulted in significant tumor regression in a xenograft model of human multiple myeloma. These results indicate that 2D7-DB acts on multiple myeloma cells differently from other bone marrow cells and thus provide the basis for a novel HLA class I-targeting therapy against multiple myeloma.
authors.affiliation: Department of Medicine and Bioregulatory Sciences, The University of Tokushima Graduate School of Health Biosciences, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Sekimoto
authors.forename: Shuji
authors.initials: S
authors.lastname: Ozaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohshima
authors.forename: Hironobu
authors.initials: H
authors.lastname: Shibata
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Abe
authors.forename: Naoki
authors.initials: N
authors.lastname: Kimura
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Hattori
authors.forename: Shigeto
authors.initials: S
authors.lastname: Kawai
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Hisafumi
authors.initials: H
authors.lastname: Yamada-Okabe
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Toshio
authors.initials: T
authors.lastname: Matsumoto
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000276:immunology / Q000473:pathology; D016923:Cell Death / Q000276:immunology; D045744:Cell Line, Tumor; D016207:Cytokines / Q000494:pharmacology; D004789:Enzyme Activation; D015234:HLA-A Antigens / Q000096:biosynthesis / Q000276:immunology*; D006801:Humans; D007116:Immunization, Passive / Q000379:methods*; D007128:Immunoglobulin Fragments / Q000494:pharmacology*; D019169:Jurkat Cells; D051379:Mice; D016513:Mice, SCID; D009101:Multiple Myeloma / Q000201:enzymology / Q000276:immunology* / Q000473:pathology / Q000628:therapy*; D023041:Xenograft Model Antitumor Assays; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D016207:Cytokines; D015234:HLA-A Antigens; D007128:Immunoglobulin Fragments; D020741:rho GTP-Binding Proteins