DPP4 truncated GM-CSF and IL-3 manifest distinct receptor-binding and regulatory functions compared with their full-length forms

Dipeptidylpeptidase 4 promotes survival and stemness of acute myeloid leukemia stem cells

Leukemic-stem-cell-specific targeting may improve the survival of patients with acute myeloid leukemia (AML) by avoiding the ablative effects of standard regimens on normal hematopoiesis. Herein, we perform an unbiased screening of compounds targeting cell surface proteins and identify clinically used DPP4 inhibitors as strong suppressors of AML development in both murine AML models and primary human AML cells xenograft model. We find in retrovirus-induced AML mouse models that DPP4-deficient AML cell-transplanted mice exhibit delay and reversal of AML development, whereas deletion of DPP4 has no significant effect on normal hematopoiesis. DPP4 activates and sustains survival of AML stem cells that are critical for AML development in both human and animal models via binding with Src kinase and activation of nuclear factor κB (NF-κB) signaling. Thus, inhibition of DPP4 is a potential therapeutic strategy against AML development through suppression of survival and stemness of AML cells.

Image-seq: spatially resolved single-cell sequencing guided by in situ and in vivo imaging

Tissue function depends on cellular organization. While the properties of individual cells are increasingly being deciphered using powerful single-cell sequencing technologies, understanding their spatial organization and temporal evolution remains a major challenge. Here, we present Image-seq, a technology that provides single-cell transcriptional data on cells that are isolated from specific spatial locations under image guidance, thus preserving the spatial information of the target cells. It is compatible with in situ and in vivo imaging and can document the temporal and dynamic history of the cells being analyzed. Cell samples are isolated from intact tissue and processed with state-of-the-art library preparation protocols. The technique therefore combines spatial information with highly sensitive RNA sequencing readouts from individual, intact cells. We have used both high-throughput, droplet-based sequencing as well as SMARTseq-v4 library preparation to demonstrate its application to bone marrow and leukemia biology. We discovered that DPP4 is a highly upregulated gene during early progression of acute myeloid leukemia and that it marks a more proliferative subpopulation that is confined to specific bone marrow microenvironments. Furthermore, the ability of Image-seq to isolate viable, intact cells should make it compatible with a range of downstream single-cell analysis tools including multi-omics protocols.

Varying Impact of Gestational Diabetes Mellitus on Incidence of Childhood Cancers: An Age-Stratified Retrospective Cohort Study

OBJECTIVE

We studied the association between gestational diabetes mellitus and early versus late childhood cancer.

RESEARCH DESIGN AND METHODS

We conducted a retrospective cohort study of 1 million children born between 2006 and 2019 in Quebec, Canada. We identified children who were exposed to gestational diabetes mellitus in utero and followed them from birth up to 14 years of age to identify new-onset cancers. We estimated hazard ratios (HRs) for the association between gestational diabetes mellitus and childhood cancer using Cox proportional regression models with adjustment for covariates through inverse propensity score weights.

RESULTS

A total of 83,626 children (8.2%) were exposed to gestational diabetes mellitus, and 1,702 developed cancer during 7.6 million person-years of follow-up. Children exposed to gestational diabetes mellitus had a higher risk of any cancer (HR 1.19, 95% CI 1.01-1.40), with signals present for blood cancer (HR 1.27, 95% CI 0.92-1.76) and solid tumors (HR 1.14, 95% CI 0.94-1.40). The association between gestational diabetes mellitus and cancer was strongest early in life and decreased with age. Gestational diabetes mellitus was associated with 1.47 times the risk of any cancer (95% CI 1.21-1.79), 1.44 times the risk of solid cancer (95% CI 1.12-1.87), and 1.61 times the risk of blood cancer (95% CI 1.09-2.36) in children age <2 years. Gestational diabetes mellitus was not significantly associated with blood or solid cancers after 2 years of age, and all associations disappeared after 6 years.

CONCLUSIONS

Hyperglycemia may be carcinogenic in utero and may be a novel risk factor for early childhood cancer.

Leukemia Inhibitory Factor Promotes Survival of Hematopoietic Progenitors Ex Vivo and Is Post-Translationally Regulated by DPP4

Hematopoietic cells are regulated in part by extracellular cues from cytokines. Leukemia inhibitory factor (LIF) promotes survival, self-renewal, and pluripotency of mouse embryonic stem cells (mESC). While genetic deletion of LIF affects hematopoietic progenitor cells (HPCs), the direct effect of LIF protein exposure on HPC survival is not known. Furthermore, post-translational modifications (PTM) of LIF and their effects on its function have not been evaluated. We demonstrate that treatment with recombinant LIF preserves mouse and human HPC numbers in stressed conditions when growth factor addition is delayed ex vivo. We show that Lif is upregulated in response to irradiation-induced stress. We reveal novel PTM of LIF where it is cleaved twice by dipeptidyl peptidase 4 (DPP4) protease so that it loses its 4 N-terminal amino acids. This truncation of LIF down-modulates LIF's ability to preserve functional HPC numbers ex vivo following delayed growth factor addition. DPP4-truncated LIF blocks the ability of full-length LIF to preserve functional HPC numbers. This LIF role and its novel regulation by DPP4 have important implications for normal and stress hematopoiesis, as well as for other cellular contexts in which LIF and DPP4 are implicated.

Pleiotropic Benefits of DPP-4 Inhibitors Beyond Glycemic Control

Dipeptidyl peptidase (DPP)-4 inhibitors are oral anti-diabetic medications that block the activity of the ubiquitous enzyme DPP-4. Inhibition of this enzyme increases the level of circulating active glucagon-like peptide (GLP)-1 secreted from L-cells in the small intestine. GLP-1 increases the glucose level, dependent on insulin secretion from pancreatic β-cells; it also decreases the abnormally increased level of glucagon, eventually decreasing the blood glucose level in patients with type 2 diabetes. DPP-4 is involved in many physiological processes other than the degradation of GLP-1. Therefore, the inhibition of DPP-4 may have numerous effects beyond glucose control. In this article, we review the pleiotropic effects of DPP-4 inhibitors beyond glucose control, including their strong beneficial effects on the stress induced accelerated senescence of vascular cells, and the possible clinical implications of these effects.

DPP4+ exosomes in AML patients' plasma suppress proliferation of hematopoietic progenitor cells

Mechanisms by which acute myeloid leukemia (AML) interferes with normal hematopoiesis are under intense investigation. Emerging evidence suggests that exosomes produced by leukemia blasts suppress hematopoiesis. Exosomes isolated from AML patients' plasma at diagnosis significantly and dose-dependently suppressed colony formation of normal hematopoietic progenitor cells (HPC). Levels of HPC suppression mediated by exosomes of AML patients who achieved complete remission (CR) were significantly decreased compared to those observed at AML diagnosis. Exosomes from plasma of patients who had achieved CR but with incomplete cell count recovery (CRi) after chemotherapy suppressed in vitro colony formation as effectively as did exosomes obtained at AML diagnosis. Dipeptidylpeptidase4 (DPP4/CD26), a serine protease that cleaves select penultimate amino acids of various proteins, has been previously implicated in the regulation of hematopoiesis. DPP4 was carried by exosomes from AML plasma or leukemia cell lines. Leukemia exosomes which suppressed HSC colony formation had markedly higher DPP4 functional activity than that detected in the exosomes of normal donors. Pharmacological inhibition of DPP4 activity in AML exosomes reversed the effects of exosome-mediated myelosuppression. Reversing the negative effects of exosomes on AML hematopoiesis, and thus improving cell count recovery, might emerge as a new therapeutic approach to AML.

An expanded role for dipeptidyl peptidase 4 in cell regulation

PURPOSE OF REVIEW

Dipeptidyl peptidase 4 (DPP4) is a serine protease with diverse regulatory functions in healthy and diseased cells. Much remains unknown about the mechanisms and targets of DPP4. Here we discuss new studies exploring DPP4-mediated cellular regulation, provide an updated list of potential targets of DPP4, and discuss clinical implications of each.

RECENT FINDINGS

Recent studies have sought enhanced efficacy of targeting DPP4's role in regulating hematopoietic stem and progenitor cells for improved clinical application. Further studies have identified DPP4 functions in different cellular compartments and have proposed ways to target this protein in malignancy. These findings, together with an expanded list of putative extracellular, cell surface, and intracellular DPP4 targets, provide insight into new DPP4-mediated cell regulation.

SUMMARY

DPP4 posttranslationally modifies proteins and peptides with essential roles in hematopoietic cell regulation, stem cell transplantation, and malignancy. Targets include secreted signaling factors and may include membrane proteins and transcription factors critical for different hematopoietic functions. Knowing these targets and functions can provide insight into new regulatory roles for DPP4 that may be targeted to enhance transplantation, treat disease, and better understand different regulatory pathways of hematopoiesis.

Cooperating, congenital neutropenia-associated Csf3r and Runx1 mutations activate pro-inflammatory signaling and inhibit myeloid differentiation of mouse HSPCs

Patients with the pre-leukemia bone marrow failure syndrome called severe congenital neutropenia (CN) have an approximately 15% risk of developing acute myeloid leukemia (AML; called here CN/AML). Most CN/AML patients co-acquire CSF3R and RUNX1 mutations, which play cooperative roles in the development of AML. To establish an in vitro model of leukemogenesis, we utilized bone marrow lin^- cells from transgenic C57BL/6-d715 Csf3r mice expressing a CN patient-mimicking truncated CSF3R mutation. We transduced these cells with vectors encoding RUNX1 wild type (WT) or RUNX1 mutant proteins carrying the R139G or R174L mutations. Cells transduced with these RUNX1 mutants showed diminished in vitro myeloid differentiation and elevated replating capacity, compared with those expressing WT RUNX1. mRNA expression analysis showed that cells transduced with the RUNX1 mutants exhibited hyperactivation of inflammatory signaling and innate immunity pathways, including IL-6, TLR, NF-kappaB, IFN, and TREM1 signaling. These data suggest that the expression of mutated RUNX1 in a CSF3R-mutated background may activate the pro-inflammatory cell state and inhibit myeloid differentiation.

The roles of dipeptidyl peptidase-4 and its inhibitors in the regulation of airway epithelial-mesenchymal transition

Objective: Dipeptidyl peptidase 4 (DPP4), also known as CD26, is a transmembrane glycoprotein with peptidase activity expressed on epithelial cells and some immune cells. It also occurs as a soluble form. Studies have revealed that the expression level of lymphocyte sCD26/sDPP4 was elevated in the asthmatic patients. Airway remodeling increases in asthma severity and these structural changes include, amongst others, the loss of epithelial integrity because of cell shedding, goblet cell hyperplasia, destruction of ciliated cells, and EMT. So we try to find whether sCD26/sDPP4 has a role in pathological/dysregulated transition from bronchial epithelial cells into fibroblasts cells in response to TGFβ1 exposure in vitro. Therefore, our purpose in the present work was to identify the role of sCD26/sDPP4 in airway EMT regulation. Methods: The EMT cell model was established based on human 16HBE cells. The effects of sCD26/sDPP4 and its inhibitors on airway EMT and that of sCD26/sDPP4 on Th17/IL-17 and its role in airway EMT were investigated in vitro. Results: The mRNA and protein level of E-Cadherin decreased after the treatment of TGF-β1 in 16HBE cells, while α-SMA was up-regulated. The level of E-Cadherin was significantly down-regulated after the sCD26/sDPP4 stimulation, and that of α-SMA was dramatically elevated. DPP4 inhibitors promoted the level of E-cadherin and inhibited that of α-SMA. Additionally, in the DPP4-treated IL-17 cells group, E-Cadherin was markedly down-regulated at the mRNA and protein level, while α-SMA was reversely up-regulated. Conclusion: The TGF-β1-induced EMT of human bronchial epithelial cells could be promoted by sCD26/sDPP4. The suppression of EMT in human bronchial epithelial cells was achieved by DPP4 inhibitor, and the TGF-β1-mediated EMT of human airway cells was promoted by the synergy of IL-17 and sCD26/sDPP4 in vitro.

Dipeptidyl peptidase 4 inhibitors and their potential immune modulatory functions

Dipeptidyl peptidase 4 (DPP4) inhibitors (DPP4is) are oral anti-diabetic drugs (OADs) for the treatment of type 2 diabetes mellitus (T2DM) through inhibiting the degradation of incretin peptides. Numerous investigations have been focused on the effects of DPP4is on glucose homeostasis. However, there are limited evidences demonstrating their Potential modulatory functions in the immune system. DPP4, originally known as the lymphocyte cell surface protein CD26, is widely expressed in many types of immune cells including CD4(+) and CD8(+) T cells, B cells, NK cells, dendritic cells, and macrophages; and regulate the functions of these cells. In addition, DPP4 is capable of modulating plenty of cytokines, chemokines and peptide hormones. Accordingly, DPP4/CD26 is speculated to be involved in various immune/inflammatory diseases and DPP4is may become a new drug class applied in these diseases. This review focuses on the regulatory effects of DPP4is on immune functions and their possible underlying mechanisms. Further clinical studies will be necessitated to fully evaluate the administration of DPP4is in diabetic patients with or without immune diseases.

Exosomes in acute myeloid leukemia inhibit hematopoiesis

PURPOSE OF REVIEW

Exosomes are cell-derived, biologically active membrane-bound vesicles, and are emerging as key modulators of hematopoiesis. Recent studies have provided a clearer understanding of the mechanisms whereby blast-derived exosomes act to suppress hematopoiesis in acute myeloid leukemia (AML).

RECENT FINDINGS

Exosomes released from leukemia blasts have been shown to suppress hematopoietic progenitor cell (HPC) functions indirectly through stromal reprogramming of niche-retention factors and also as a consequence of AML exosome-directed microRNA delivery to HPC. Furthermore, exosomes secreted by AML blasts remodel the bone marrow niche into a leukemia growth-permissive microenvironment.

SUMMARY

Exosomes suppress hematopoiesis in AML. Strategies to block the production, secretion and reprogramming that exosomes induce may be a novel therapeutic approach in AML and other leukemias.

A novel non-enzymatic hydrolytic probe for dipeptidyl peptidase IV specific recognition and imaging

A novel non-enzymatic hydrolytic probe for DPP IV is obtained.

Open the gates: vascular neurocrine signaling mobilizes hematopoietic stem and progenitor cells

Mobilization of hematopoietic stem and progenitor cells (HSPCs) from the bone marrow (BM) into the peripheral blood is a complex process that is enhanced dramatically under stress-induced conditions. A better understanding of how the mobilization process is regulated will likely facilitate the development of improved clinical protocols for stem cell harvesting and transplantation. In this issue of the JCI, Singh et al. (1) showed that the truncated cleaved form of neurotransmitter neuropeptide Y (NPY) actively promotes a breach of BM vascular sinusoidal portals, thereby augmenting HSPC trafficking to the circulation. The authors report a previously unrecognized axis, in which expression of the enzyme dipeptidylpeptidase-4 (DPP4)/CD26 by endothelial cells activates NPY-mediated signaling by increasing the bioavailability of the truncated form of NPY. These findings underscore the importance of and urgency to develop pharmacological therapies that target the vasculature and regulate diverse aspects of hematopoiesis, such as HSPC trafficking, in steady-state and stress-induced conditions.

Chemokine isoforms and processing in inflammation and immunity

The first dimension of chemokine heterogeneity is reflected by their discovery and purification as natural proteins. Each of those chemokines attracted a specific inflammatory leukocyte type. With the introduction of genomic technologies, a second wave of chemokine heterogeneity was established by the discovery of putative chemokine-like sequences and by demonstrating chemotactic activity of the gene products in physiological leukocyte homing. In the postgenomic era, the third dimension of chemokine heterogeneity is the description of posttranslational modifications on most chemokines. Proteolysis of chemokines, for instance by dipeptidyl peptidase IV (DPP IV/CD26) and by matrix metalloproteinases (MMPs) is already well established as a biological control mechanism to activate, potentiate, dampen or abrogate chemokine activities. Other posttranslational modifications are less known. Theoretical N-linked and O-linked attachment sites for chemokine glycosylation were searched with bio-informatic tools and it was found that most chemokines are not glycosylated. These findings are corroborated with a low number of experimental studies demonstrating N- or O-glycosylation of natural chemokine ligands. Because attached oligosaccharides protect proteins against proteolytic degradation, their absence may explain the fast turnover of chemokines in the protease-rich environments of infection and inflammation. All chemokines interact with G protein-coupled receptors (GPCRs) and glycosaminoglycans (GAGs). Whether lectin-like GAG-binding induces cellular signaling is not clear, but these interactions are important for leukocyte migration and have already been exploited to reduce inflammation. In addition to selective proteolysis, citrullination and nitration/nitrosylation are being added as biologically relevant modifications contributing to functional chemokine heterogeneity. Resulting chemokine isoforms with reduced affinity for GPCRs reduce leukocyte migration in various models of inflammation. Here, these third dimension modifications are compared, with reflections on the biological and pathological contexts in which these posttranslational modifications take place and contribute to the repertoire of chemokine functions and with an emphasis on autoimmune diseases.