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Dipeptidyl peptidase 9 (DPP9) is a ubiquitously expressed intracellular prolyl peptidase implicated in immunoregulation. However, its physiological relevance in the immune system remains largely unknown. We investigated the role of DPP9 enzyme in immune system by characterizing DPP9 knock-in mice expressing a catalytically inactive S729A mutant of DPP9 enzyme (DPP9ki/ki mice). DPP9ki/ki mice show reduced number of lymphoid and myeloid cells in fetal liver and postnatal blood but their hematopoietic cells are fully functional and able to reconstitute lymphoid and myeloid lineages even in competitive mixed chimeras. These studies demonstrate that inactivation of DPP9 enzymatic activity does not lead to any perturbations in mouse hematopoiesis.

Dipeptidyl peptidase 9 (DPP9) is an intracellular N-terminal post-proline-cleaving enzyme whose physiological function remains largely unknown. We investigated the role of DPP9 enzyme in vivo by characterizing knock-in mice expressing a catalytically inactive mutant form of DPP9 (S729A; DPP9 ki/ki mice). We show that DPP9 ki/ki mice die within 12–18 h after birth. The neonatal lethality can be rescued by manual feeding, indicating that a suckling defect is the primary cause of neonatal lethality. The suckling defect results from microglossia, and is characterized by abnormal formation of intrinsic muscles at the distal tongue. In DPP9 ki/ki mice, the number of occipital somite-derived migratory muscle progenitors, forming distal tongue intrinsic muscles, is reduced due to increased apoptosis. In contrast, intrinsic muscles of the proximal tongue and extrinsic tongue muscles, which derive from head mesoderm, develop normally in DPP9 ki/ki mice. Thus, lack of DPP9 activity in mice leads to impaired tongue development, suckling defect and subsequent neonatal lethality due to impaired survival of a specific subset of migratory tongue muscle progenitors.

As the recent rise of immune checkpoint inhibitors has resulted in durable clinical outcomes in cancer patients, the need for a newer and more widely effective target for immunotherapy has been vigorously sought in the field; T cell immunoreceptor with Ig and ITIM domain (TIGIT) is an immune checkpoint molecule expressed on CD8+ T cells, CD4+ T cells, NK cells, and regulatory T cells (Treg). TIGIT induces exhaustion of effector T cells (Teff) and NK cells in the tumor microenvironment via engagement with its ligand PVR (CD155) which is dominantly expressed on malignant tumor cells. After initial screening processes from a synthetic library, MG1131 clone was chosen based on the strongest binding affinity to human TIGIT and the superior PVR-blocking activity. MG1131 was cross-reactive with the cynomolgus monkey TIGIT, but not with the mouse TIGIT. Our in vitro efficacy data demonstrated that MG1131 activated NF-κB signaling in T cells, and enhanced NK-mediated tumor killing activities in a PVR-dependent manner. In vitro Treg suppression assays showed that MG1131 inhibited immunosuppressive functionality of Treg, leading to restoration of proliferation and IFN-γ secretion capacities of Teff even in the presence of Treg. In addition, expression levels of TIGIT on CD8+ T cells from PBMCs of cancer patient samples were higher compared with other immune inhibitory molecules such as PD-1, Tim-3, CTLA-4, or LAG-3, and the blockade of TIGIT by MG1131 resulted in increased IFN-γ secretion. Thus, our data indicate that MG1131 is a promising candidate for cancer immunotherapy by modulating NK and T cell functions. Citation Format: Jeewon Lee, Munkyung Kim, Hye-mi Nam, Joong Hyuk Sheen, Eun Jung Song, Hye In Yum, So Jung Lim, Hye-Young Park. MG1131, a novel TIGIT-targeting monoclonal antibody, enhances anti-tumor immune responses by modulating NK and T cell activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2230.

Mesothelin (MSLN) is an antigen overexpressed in several malignancies, including mesothelioma and ovarian and pancreatic adenocarcinoma. It has been studied as a marker for diagnosis and a target for immunotherapy. Here, we adopted a bispecific antibody format for recruiting cytotoxic T cells to kill tumor cells. MG1122 is a novel, whole IgG-like bispecific antibody which recognizes CD3 on T cells and MSLN on tumor cells. MG1122 induced effective killing of MSLN-expressing tumor cells. This response was associated with robust activation of T cells as shown by nuclear factor of activated T cells (NFAT) activation, CD25 and CD69 upregulation and increased cytokine release. In addition, using a live cell analysis system, we found that levels of activated caspase 3/7 were amplified in the tumor cells by MG1122 treatment. Although MSLN is a surface antigen, it also exists as a secreted isoform, which can lead to tumor evasion against MSLN targeting antibodies. However, despite the high concentration of soluble MSLN, MG1122 still effectively bound and showed strong killing effects against MSLN-expressing tumor cells. Taken together, our MSLN/CD3 bispecific antibody, MG1122 offers a promising opportunity to redirect T cells to kill MSLN-expressing cancer cells. Citation Format: Yun-Jung Lee, Okjae Lim, Munkyung Kim, Jeewon Lee, Kisu Kim, Junhong Jung, SuA Lee, Sung Keun Kim, Haenaem Kwon, Yangmi Lim, Yong Yea Park, Jonghwa Won. MG1122, a whole IgG-like bispecific antibody targeting mesothelin and CD3, induces T cell-mediated killing of MSLN-expressing tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5768.

The oxidation kinetics of TiAl alloys with and without (3, 5, 10 wt.%) TiB2 dispersoids were studied between 1073 and 1273 K in atmospheric air. The inert TiB2 dispersoids effectively increased the oxidation resistance of TiAl alloys. The higher the TiB2 dispersoids content, the more pronounced the effect. The oxide scale formed on TiAl–TiB2 composites was triple-layered, consisting mainly of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (TiO2+Al2O3) mixed layer. No B2O3 was observed within the oxide scale because of its high vapor pressure. A thin Ti3Al sublayer and discrete TiN particles were found at the oxide–substrate interface. During the oxidation of TiAl alloys with and without TiB2 dispersoids, titanium ions diffused outwardly to form the outer TiO2 layer, while oxygen ions transported inwardly to form the inner (TiO2+Al2O3) mixed layer. The increased oxidation resistance by the addition of TiB2 was attributed to the enhanced alumina-forming tendency and thin and dense scale formation.

Reversine has been shown to induce dedifferentiation of C2C12 murine myoblasts into multipotent progenitor cells. However, little is known about the key regulators mediating the dedifferentiation induced by reversine. Here, we show that large scale miRNA gene expression profiling of reversine-treated C2C12 myoblasts identifies a down-regulated miRNA, miR-133a, involved in dedifferentiation of myoblasts. Reversine treatment results in up- and down-regulated miRNA profiles. Among miRNAs affected by reversine, the level of muscle-specific miR-133a, which has been shown to be up-regulated during muscle development and to suppress differentiation into other lineages, is markedly reduced by treatment of C2C12 myoblasts with reversine. In parallel, reversine decreases the expression and recruitment of myogenic factor, SRF, to the enhancer regions of miR-133a. Sequentially, down-regulation of miR-133a by reversine is accompanied by a decrease in active histone modifications including trimethylation of histone H3K4 and H3K36, phosphorylation of H3S10, and acetylation of H3K14 on the miR-133a promoter, leading to dissociation of RNA polymerase II from the promoter. Furthermore, inhibition of miR-133a by transfection of C2C12 myoblasts with miR-133a inhibitor increases the expression of osteogenic lineage marker, Ogn, and adipotenic lineage marker, ApoE, similar to that in response to reversine. In contrast, the co-overexpression of miR-133a mimic reversed the effect of reversine on C2C12 myoblast dedifferentiation. Taken together, the results indicate that reversine induces a multipotency of C2C12 myoblasts by suppression of miR-133a expression through depletion of active histone modifications, and suggest that miR-133a is a potential miRNA regulating the reversine-induced dedifferentiation. Collectively, our findings provide a mechanistic rationale for the application of reversine to dedifferentiation of somatic cells.