Chimeric-antigen-receptor (CAR) T-cell therapy for CD19-expressing B-cell malignancies is already widely adopted in clinical practice. On the other hand, the development of CAR-T-cell therapy for T-cell malignancies is in its nascent stage. One of the potential targets is CD26, to which we have developed and evaluated the efficacy and safety of the humanized monoclonal antibody YS110. We generated second (CD28) and third (CD28/4-1BB) generation CD26-targeted CAR-T-cells (CD26-2G/3G) using YS110 as the single-chain variable fragment. When co-cultured with CD26-overexpressing target cells, CD26-2G/3G strongly expressed the activation marker CD69 and secreted IFNgamma. In vitro studies targeting the T-cell leukemia cell line HSB2 showed that CD26-2G/3G exhibited significant anti-leukemia effects with the secretion of granzymeB, TNFα, and IL-8, with 3G being superior to 2G. CD26-2G/3G was also highly effective against T-cell lymphoma cells derived from patients. In an in vivo mouse model in which a T-cell lymphoma cell line, KARPAS299, was transplanted subcutaneously, CD26-3G inhibited tumor growth, whereas 2G had no effect. Furthermore, in a systemic dissemination model in which HSB2 was administered intravenously, CD26-3G inhibited tumor growth more potently than 2G, resulting in greater survival benefit. The third-generation CD26-targeted CAR-T-cell therapy may be a promising treatment modality for T-cell malignancies.

DPP8/9 inhibition induces either pyroptotic or apoptotic cell death in hematological malignancies. We previously reported that treatment with the DPP8/9 inhibitor 1G244 resulted in apoptotic cell death in myeloma, and our current study further evaluates the mechanism of action of 1G244 in different blood cancer cell lines. Specifically, 1G244 inhibited DPP9 to induce GSDMD-mediated-pyroptosis at low concentrations and inhibited DPP8 to cause caspase-3-mediated-apoptosis at high concentrations. HCK expression is necessary to induce susceptibility to pyroptosis but does not participate in the induction of apoptosis. To further characterize this DPP8-dependent broad-spectrum apoptosis induction effect, we evaluated the potential antineoplastic role for an analog of 1G244 with higher DPP8 selectivity, tominostat (also known as 12 m). In vitro studies demonstrated that the cytotoxic effect of 1G244 at high concentrations was enhanced in tominostat. Meanwhile, in vivo work showed tominostat exhibited antitumor activity that was more effective on a cell line sensitive to 1G244, and at higher doses, it was also effective on a cell line resistant to 1G244. Importantly, the weight loss morbidity associated with increasing doses of 1G244 was not observed with tominostat. These results suggest the possible development of novel drugs with antineoplastic activity against selected hematological malignancies by refining and increasing the DPP8 selectivity of tominostat.

CD26 (dipeptidyl peptidase-4) is a marker of colorectal cancer stem cells with high metastatic potential and resistance to therapy. Although CD26 expression is known to be associated with tumor progression, its functional involvement in epithelial-mesenchymal transition (EMT) and metastasis remains to be fully elucidated. In this study, we aimed to investigate the effects of a monoclonal anti-CD26 antibody on EMT-related phenotypes and metastatic behavior in colorectal cancer cells. We evaluated changes in EMT markers by quantitative PCR and Western blotting, assessed cell motility and invasion using scratch wound-healing and Transwell assays, and examined metastatic potential in vivo using a splenic injection mouse model. Treatment with the anti-CD26 antibody significantly increased the expression of the epithelial marker E-cadherin and reduced levels of EMT-inducing transcription factors, including ZEB1, Twist1, and Snail1, at the mRNA and protein levels. Functional assays revealed that the antibody markedly inhibited cell migration and invasion in vitro without exerting cytotoxic effects. Furthermore, systemic administration of the anti-CD26 antibody significantly suppressed the formation of liver metastases in vivo. These findings suggest that CD26 may contribute to the regulation of EMT and metastatic behavior in colorectal cancer. Our data highlight the potential therapeutic utility of CD26-targeted antibody therapy for suppressing EMT-associated phenotypes and metastatic progression.