A novel bispecific protein (ULBP2-BB4) targeting the NKG2D receptor on natural killer (NK) cells and CD138 activates NK cells and has potent antitumor activity against human multiple myeloma in vitro and in vivo

Abstract

The inability of the immune system to recognize and kill malignant plasma cells in patients with multiple myeloma (MM) has been attributed in part to the ineffective activation of natural killer (NK) cells. In order to activate and target NK cells to the malignant cells in MM we designed a novel recombinant bispecific protein (ULBP2-BB4). While ULBP2 binds the activating NK receptor NKG2D, the BB4 moiety binds to CD138, which is overex-pressed on a variety of malignancies, including MM. ULBP2-BB4 strongly activated primary NK cells as demonstrated by a significant increase in interferon-(IFN-) secretion. In vitro, ULBP2-BB4 enhanced the NK-mediated lysis of 2 CD138 human MM cell lines, U-266 and RPMI-8226, and of primary malignant plasma cells in the allogenic and autolo-gous setting. Moreover, in a nude mouse model with subcutaneously growing RPMI-8226 cells, the cotherapy with ULBP-BB4 and human peripheral blood lympho-cytes abrogated the tumor growth. These data suggest potential clinical use of this novel construct in patients with MM. The use of recombinant NK receptor ligands that target NK cells to tumor cells might offer new approaches for other malignan-cies provided a tumor antigen-specific antibody is available. (Blood. 2006;107: 1955-1962)

Mimicking an Induced Self Phenotype by Coating Lymphomas with the NKp30 Ligand B7-H6 Promotes NK Cell Cytotoxicity

“…However, these strategies did not allow tumor-specific NK cell activation. In another more tumor-specific approach, tumor cells were opsonized with bifunctional Ab-based fusion proteins containing ligands addressing NKG2D (25)(26)(27). Fusion proteins containing scFvs against tumor-associated Ags such as CD20, CD33, or CD138 were able to mediate NK cell cytotoxicity.…”

“…Alternatively, tumor cells were exogenously coated with such danger signals by using recombinant immunoligands. These are bifunctional fusion proteins consisting of a stimulatory ligand and a tumor-directed Ab fragment that represent an attractive class of molecules with immunomodulatory functions (25)(26)(27). However, most attempts have focused on the NKG2D ligand system, whereas to date NKp30 and other NCRs have not been investigated as stimulatory molecules for potential therapeutic purposes.…”

Mono- and dual-targeting triplebodies activate natural killer cells and have anti-tumor activityin vitroandin vivoagainst chronic lymphocytic leukemia

“…19 We reported the first such immunoligand, ULBP2-BB4 (scFv against CD138), which successfully activated and retargeted NK cells through ULBP2 against CD138-positive multiple myeloma cells both in vitro and in vivo. 20 Subsequently, two additional immunoligands in similar formats, ULBP2-aCEA (scFv against CEA) 21 and ULBP2-aPSMA (scFv against PSMA) 22 and immunoligands fused to other ligands, [23][24][25] validated our approach. Several trispecific immunoconstructs targeting the FcgRIIIa receptor on NK cells have been developed and compared with their bispecific counterparts.…”

“…19,30 So far, these novel approaches mainly involved bispecific recombinant proteins by our group and others to exploit NKG2D-dependent NK cell activation against tumor. [19][20][21] In this study, our strategy was to design NKG2D-triggering triplebodies that involved targeting of CD19 antigen or CD19/CD33 in combination. ULBP2-aCD19-aCD19 targets CD19 on CLL cells by two subsequent antiCD19 scFvs separated by 20 amino acid long Gly/Ser linker.…”

“…IL-15 has previously shown to upregulate NKG2D expression on NK cells and hence purified NK cells were overnight incubated with IL-2 and IL-15. 20 FACS-based toxicity assay was performed by incubating target cells (MEC1 or HL60) with purified NK cells with or without 10 nM of ULBP2-aCD19 and ULBP2-aCD19-aCD19 immunoligands for 3 h at indicated effector to target (E:T) ratios. Both immunoligands enhanced NKcell-dependent killing of MEC1 cells in E:T-ratio-dependent manner (Fig.…”