Dipeptidyl peptidases (DPPs) are proteolytic enzymes that are ideal therapeutic targets in human diseases. Indeed, DPP4 inhibitors are widely used in clinical practice as anti-diabetic agents. In this paper, we show that DPP4 inhibitors also induced cell death in multiple human myeloma cells. Among five DPP4 inhibitors, only two of them, vildagliptin and saxagliptin, exhibited apparent cytotoxic effects on myeloma cell lines, without any difference in suppression of DPP4 activity. As these two DPP4 inhibitors are known to have off-target effects against DPP8/9, we employed the specific DPP8/9 inhibitor 1G244. 1G244 demonstrated anti-myeloma effects on several cell lines and CD138+ cells from patients as well as in murine xenograft model. Through siRNA silencing approach, we further confirmed that DPP8 but not DPP9 is a key molecule in inducing cell death induced by DPP8/9 inhibition. In fact, the expression of DPP8 in CD38+ cells from myeloma patients was higher than that of healthy volunteers. DPP8/9 inhibition induced apoptosis, as evidenced by activated form of PARP, caspases-3 and was suppressed by the pan-caspase inhibitor Z-VAD-FMK. Taken together, these results indicate that DPP8 is a novel therapeutic target for myeloma treatment.

Pericyte desorption from retinal blood vessels and subsequent vascular abnormalities are the pathogenesis of diabetic retinopathy (DR). Although the involvement of abnormal signals including platelet-derived growth factor receptor-β (PDGFRβ) and vascular endothelial growth factor-A (VEGF-A) have been hypothesized in DR, the mechanisms that underlie this processes are largely unknown. Here, novel retinopathy mouse model (N-PRβ-KO) was developed with conditional Pdgfrb gene deletion by Nestin promoter-driven Cre recombinase (Nestin-Cre) that consistently reproduced through early non-proliferative to late proliferative DR pathologies. Depletion of Nestin-Cre-sensitive PDGFRβ+NG2+αSMA− pericytes suppressed pericyte-coverages and induced severe vascular lesion and hemorrhage. Nestin-Cre-insensitive PDGFRβ+NG2+αSMA+ pericytes detached from the vascular wall, and subsequently changed into myofibroblasts in proliferative membrane to cause retinal traction. PDGFRα+ astrogliosis was seen in degenerated retina. Expressions of placental growth factor (PlGF), VEGF-A and PDGF-BB were significantly increased in the retina of N-PRβ-KO. PDGF-BB may contribute to the pericyte-fibroblast transition and glial scar formation. Since VEGFR1 signal blockade significantly ameliorated the vascular phenotype in N-PRβ-KO mice, the augmented VEGFR1 signal by PlGF and VEGF-A was indicated to mediate vascular lesions. In addition to PDGF-BB, PlGF and VEGF-A with their intracellular signals may be the relevant therapeutic targets to protect eyes from DR.

Intravascular large B-cell lymphoma (IVLBCL) is a very rare subtype of malignant lymphoma that is difficult to diagnose. Cases of myocardial infarction caused by IVLBCL are even rarer. Herein, we report a case presenting with heart failure and delayed enhancement in the hypokinetic cardiac septum on contrast-enhanced cardiac magnetic resonance imaging. Myocardial biopsy showed large B-cell lymphoma cells in the microvessels within the myocardium. To the best of our knowledge, this is the first report of imaging findings of cardiac involvement in IVLBCL.

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