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Background: Asthma pathology may induce changes in naïve/memory lymphocyte proportions assessable through the evaluation of surface CD26 (dipeptidyl peptidase 4/DPP4) levels. Our aim was to investigate the association of asthma phenotype/severity with the relative frequency of CD26−/lo, CD26int and CD26hi subsets within different lymphocyte populations. Methods: The proportion of CD26−/lo, CD26int and CD26hi subsets within CD4+ effector T cells (Teff), total CD4− lymphocytes, γδ‐T cells, NK cells and NKT cells was measured in peripheral blood samples from healthy (N = 30) and asthma (N = 119) donors with different phenotypes/severities by flow cytometry. We performed K‐means clustering analysis and further characterised the CD4+CD26−/lo Teff cell subset by LC–MS/MS and immunofluorescence. Results: Cluster analysis including clinical and flow cytometry data resulted in four groups, two of them with opposite inflammatory profiles (neutrophilic vs. eosinophilic). Neutrophilic asthma presented reduced CD4−CD26hi cells, which negatively correlated with systemic inflammation. Eosinophilic asthma displayed a general expansion of CD26−/lo subsets. Specifically, CD4+CD26−/lo Teff expansion was confirmed in asthma, especially in atopic patients. Proteomic characterisation of this subset with a TEM/TEMRA phenotype revealed upregulated levels of innate (e.g. MPO and RNASE2) and cytoskeleton/extracellular matrix (e.g. MMP9 and ACTN1) proteins. Immunofluorescence assays confirmed the presence of atypical proteins for CD4+ T cells, and an enrichment in 'flower‐like' nuclei and MMP9/RNASE2 levels in CD4+CD26−/lo Teff compared to CD4+ T lymphocytes. Conclusion: There is an association between CD26 levels in different lymphocyte subsets and asthma phenotype/severity. CD4+CD26−/loTEMRA cells expressing innate proteins specific to eosinophils/neutrophils could be determinant in sustaining long‐term inflammation in adult allergic asthma. [ABSTRACT FROM AUTHOR]

Introduction: Leukemic stem cells (LSCs) are the transcriptionally low/silent cells which are resistant to the tyrosine kinase inhibitor. These have been found to play a pivotal role in disease relapse in chronic myeloid leukemia (CML) cases. The present study evaluated the correlation of absolute CML‐LSC count in the peripheral blood (PB) at diagnosis and achievement of major molecular response (MMR) at 12 months in patients of CML‐CP. Methods: This was a prospective, observational, non‐interventional single center study including newly diagnosed adult (>18 yrs) CML‐CP patients. Absolute CD26 + CML‐LSC quantification was done by multiparametric flow cytometry. Patients were treated with Imatinib treatment and subsequently monitored at 3‐month intervals for BCR::ABL transcript levels. MMR was defined as a BCR::ABL1 transcript level of less than 0.1% on international scale. Results: A total of 89 patients were enrolled in the study out of which 40.5% achieved MMR at 12 months. There was a significant difference in the median absolute CML‐LSC count of the patients who achieved MMR at 12 months as compared to those who did not (58.5 vs 368.1 cells/μL; p value <0.001). Using a ROC analysis, a count of <165.69 CML LSC/μL was identified to have a sensitivity of 83.8% and specificity of 72.4%, in predicting the MMR at 12 months. Conclusion: Absolute CML‐LSC count at diagnosis in the PB predicts the MMR achievement at 12 months. An absolute count of less than 165 cells/μL is highly predictive of achieving MMR at 12 months. [ABSTRACT FROM AUTHOR]

Infantile hemangiomas (IHs) are benign vascular neoplasms of childhood (prevalence 5–10%) due to the abnormal proliferation of endothelial cells. IHs are characterized by a peculiar natural life cycle enclosing three phases: proliferative (≤12 months), involuting (≥13 months), and involuted (up to 4–7 years). The mechanisms underlying this neoplastic disease still remain uncovered. Twenty-seven IH tissue specimens (15 proliferative and 12 involuting) were subjected to hematoxylin and eosin staining and a panel of diagnostic markers by immunohistochemistry. WT1, nestin, CD133, and CD26 were also analyzed. Moreover, CD31pos/CD26pos proliferative hemangioma–derived endothelial cells (Hem-ECs) were freshly isolated, exposed to vildagliptin (a DPP-IV/CD26 inhibitor), and tested for cell survival and proliferation by MTT assay, FACS analysis, and Western blot assay. All IHs displayed positive CD31, GLUT1, WT1, and nestin immunostaining but were negative for D2-40. Increased endothelial cell proliferation in IH samples was documented by ki67 labeling. All endothelia of proliferative IHs were positive for CD26 (100%), while only 10 expressed CD133 (66.6%). Surprisingly, seven involuting IH samples (58.3%) exhibited coexisting proliferative and involuting aspects in the same hemangiomatous lesion. Importantly, proliferative areas were characterized by CD26 immunolabeling, at variance from involuting sites that were always CD26 negative. Finally, in vitro DPP-IV pharmacological inhibition by vildagliptin significantly reduced Hem-ECs proliferation through the modulation of ki67 and induced cell cycle arrest associated with the upregulation of p21 protein expression. Taken together, our findings suggest that CD26 might represent a reliable biomarker to detect proliferative sites and unveil non-regressive IHs after a 12-month life cycle. [ABSTRACT FROM AUTHOR]

Background/Objectives: Colorectal cancer (CRC) is still accompanied by significant mortality, which poses the necessity of novel markers to predict treatment success and patient survival. This study aims to evaluate the prognostic and survival impact of flowytometry (FC) in CRC patients. Methods: In this prospective study, 106 surgically resectable CRC patients were included. Tissue specimens from tumor and normal mucosa were collected and analyzed by FC. DNA and tumor index were calculated. In a subgroup of 46 patients, the CD26 expression on tumor cells was estimated. These parameters were compared with patients' tumor characteristics as stage, histology data, responsiveness to treatment, metastasis/recurrence, and, finally, patients' survival to identify possible new biomarkers. Results: The overall survival and the disease-specific survival in our study group was 76% and 72%, respectively, during the 7-year follow up period. Diploid tumors had better median survival than the aneuploid ones. The DNA index had significant correlation to the tumor index and response to neoadjuvant treatment. Similarly, the tumor index was also significantly related to the response to neoadjuvant treatment. Patients with a higher tumor index had worst survival rates. Surprisingly, CD26 levels were not associated with any of the parameters examined and were negatively related to tumor stage and differentiation. Conclusions: FC is a rapid and reliable method of cell analysis. In CRC, it has been used for prognostic and diagnostic purposes. In this study, we have shown that DNA and tumor index could become predictive biomarkers of tumor response to neoadjuvant treatment and survival of resectable CRC patients. [ABSTRACT FROM AUTHOR]

A novel pangolin-origin MERS-like coronavirus (CoV), MjHKU4r-CoV-1, was recently identified. It is closely related to bat HKU4-CoV, and is infectious in human organs and transgenic mice. MjHKU4r-CoV-1 uses the dipeptidyl peptidase 4 (DPP4 or CD26) receptor for virus entry and has a broad host tropism. However, the molecular mechanism of its receptor binding and determinants of host range are not yet clear. Herein, we determine the structure of the MjHKU4r-CoV-1 spike (S) protein receptor-binding domain (RBD) complexed with human CD26 (hCD26) to reveal the basis for its receptor binding. Measuring binding capacity toward multiple animal receptors for MjHKU4r-CoV-1, mutagenesis analyses, and homology modeling highlight that residue sites 291, 292, 294, 295, 336, and 344 of CD26 are the crucial host range determinants for MjHKU4r-CoV-1. These results broaden our understanding of this potentially high-risk virus and will help us prepare for possible outbreaks in the future. Synopsis: MjHKU4r-CoV-1 is a novel merbecovirus with potentially high risk. This study elucidates the molecular mechanism of its receptor recognition and broad host tropism, enhancing our understanding of MjHKU4r-CoV-1 to prepare for possible future outbreaks. Determination of the X-ray structure of MjHKU4r-CoV-1 RBD in complex with hCD26. Evaluation of binding of MjHKU4r-CoV-1 RBD to 17 additional CD26 orthologs. Residue sites 291, 292, 294, 295, 336, and 344 of CD26 are the crucial host range determinants for MjHKU4r-CoV-1. MjHKU4r-CoV-1 is a novel merbecovirus with potentially high risk. This study elucidates the molecular mechanism of its receptor recognition and broad host tropism, enhancing our understanding of MjHKU4r-CoV-1 to prepare for possible future outbreaks. [ABSTRACT FROM AUTHOR]

Simple Summary: Prognostic markers have become a promising tool for predicting response to a certain treatment and qualifying patients for a certain therapy; however, it is important to consider that they generally describe a probabilistic scenario. For instance, the analysis of programmed death ligand 1 expression on tumor cells or tumor mutational burden is commonly employed as a biomarker with relative predictive value for immunotherapy efficacy in non-small-cell lung cancer (NSCLC) patients. Cutting-edge techniques, such as next-generation sequencing of tumor tissue and flow cytometry analysis of lymphocyte subpopulations in the peripheral blood of patients, are used with the aim of increasing the predictive value, avoiding statistical weakness and discovering algorithms based on many biomarkers. To resolve the issues posed by these novel techniques, dynamic monitoring of biomarker changes can indicate resistance or response to immunotherapy during different points of the treatment. Hence, clinicians can flexibly modify the therapy course for the benefit of the patient, improving response rates, efficiency in laboratory routines, and the economic cost of the technique. Immune checkpoint immunotherapy alters the local (solid tumor infiltration) and systemic balance among several immune system cell populations. The usefulness of immune-cell-related soluble CD26 and its DPP4 activity in immunotherapy monitoring is discussed. Soluble CD26 (sCD26), a glycoprotein with dipeptidyl peptidase (DPP4) enzymatic activity, can contribute to early diagnosis of colorectal cancer and advanced adenomas and has been studied, including for prognostic purposes, across various other types of cancer and disease. The latest research in this field has confirmed that most, though not all, serum/plasma sCD26 is related to inflammation. The shedding and/or secretion of sCD26 from different immune cells are being investigated, and blood DPP4 activity levels do not correlate very strongly with protein titers. Some of the main substrates of this enzyme are key chemokines involved in immune cell migration, and both soluble and cell-surface CD26 can bind adenosine deaminase (ADA), an enzyme involved in the metabolism of immunosuppressor extracellular adenosine. Of note, there are T cells enriched in CD26 expression and, in mice tumor models, tumor infiltrating lymphocytes exhibited heightened percentages of CD26+ correlating with tumor regression. We employed sCD26 as a biomarker in the follow-up after curative resection of colorectal cancer for the early detection of tumor recurrence. Changes after treatment with different biological disease-modifying antirheumatic drugs, including Ig-CTLA4, were also observed in rheumatoid arthritis. Serum soluble CD26/DPP4 titer variation has recently been proposed as a potential prognostic biomarker after a phase I trial in cancer immunotherapy with a humanized anti-CD26 antibody. We propose that dynamic monitoring of sCD26/DPP4 changes, in addition to well-known inflammatory biomarkers such as CRP already in use as informative for immune checkpoint immunotherapy, may indicate resistance or response during the successive steps of the treatment. As tumor cells expressing CD26 can also produce sCD26, the possibility of sorting immune- from non-immune-system-originated sCD26 is discussed. [ABSTRACT FROM AUTHOR]

Immune cell function is impaired in hyperglycemic patients with diabetes but thought to improve with normalization of blood glucose levels. In this study, we hypothesized that this improvement might involve changes in T cell function. We compared the peripheral T cell markers between the people with and without type 2 diabetes (T2D) admitted to our hospital for glycemic control, and then in patients with T2D before and after the improvement of hyperglycemia by inpatient treatment. Expression of programmed death 1 (PD-1) and T-cell immunoglobulin and mucin domain 3 (TIM-3), co-suppressive molecules, CD26 and CD28 on CD4-positive and/or CD8-positive T cells, the Th1/Th2 ratio, and the number of regulatory T cells (Tregs) were not significantly different between the people with and without T2D. Although an average of 10.6 days of inpatient treatment with improved hyperglycemia did not affect expression of PD-1 and TIM-3 in T cells, the Th1/Th2 ratio, or Tregs, it significantly reduced expression of CD26 and CD28 on CD4-positive T cells. CD26 and CD28 on CD4-positive T cells may be associated with the altered immune function after rapid improvement of hyperglycemia but that the other T-cell markers investigated here may not be. [ABSTRACT FROM AUTHOR]

Improving cancer immunotherapy efficacy hinges on identifying key T-cell populations critical for tumor control and response to Immune Checkpoint Blockade (ICB). We have recently reported that while the co-expression of PD-1 and CD28 is associated with impaired functionality in peripheral blood, it significantly enhances T-cell fitness in the tumor site of non-small cell lung cancer (NSCLC) patients. To uncover the underlying mechanisms, we explored the role of CD26, a key player in T-cell activation through its interaction with adenosine deaminase (ADA), a crucial intra/extracellular enzyme able to neutralize local adenosine (ADO). We found that an autocrine ADA/CD26 axis enhances CD8+PD-1+CD28+ T-cell function, particularly within an immunosuppressive environment marked by CD39 expression. Then, we interrogated the TCGA and OAK datasets to gain insight into the prognostic/predictive potential of our findings. We identified a signature predicting overall survival (OS) in LUAD patients and response to atezolizumab in advanced LUAD cases. These findings suggest promising avenues for therapeutic intervention targeting the ADA/CD26 axis.

A new approach helps examine the proportion of cancerous and healthy stem cells in patients with chronic myeloid leukemia and how this influences treatment outcomes.

The advent of tyrosine kinase inhibitors (TKIs) as treatment of chronic myeloid leukemia (CML) is a paradigm in molecularly targeted cancer therapy. Nonetheless, TKI-insensitive leukemia stem cells (LSCs) persist in most patients even after years of treatment and are imperative for disease progression as well as recurrence during treatment-free remission (TFR). Here, we have generated high-resolution single-cell multiomics maps from CML patients at diagnosis, retrospectively stratified by BCR::ABL1IS (%) following 12 months of TKI therapy. Simultaneous measurement of global gene expression profiles together with >40 surface markers from the same cells revealed that each patient harbored a unique composition of stem and progenitor cells at diagnosis. The patients with treatment failure after 12 months of therapy had a markedly higher abundance of molecularly defined primitive cells at diagnosis compared to the optimal responders. The multiomic feature landscape enabled visualization of the primitive fraction as a mixture of molecularly distinct BCR::ABL1+ LSCs and BCR::ABL1-hematopoietic stem cells (HSCs) in variable ratio across patients, and guided their prospective isolation by a combination of CD26 and CD35 cell surface markers. We for the first time show that BCR::ABL1+ LSCs and BCR::ABL1- HSCs can be distinctly separated as CD26+CD35- and CD26-CD35+, respectively. In addition, we found the ratio of LSC/HSC to be higher in patients with prospective treatment failure compared to optimal responders, at diagnosis as well as following 3 months of TKI therapy. Collectively, this data builds a framework for understanding therapy response and adapting treatment by devising strategies to extinguish or suppress TKI-insensitive LSCs.

Objective To explore the effect of chenodeoxycholic acid (CDCA) on the expression of glucagon-like peptide-1 (GLP-1) in the intestine of mice induced by high-fat diet (HFD) through farnesoid X receptor (FXR), and investigate the related mechanism. Methods Forty C57BL/6 mice were divided into control group, HFD group, HFD+CDCA group, HFD+Z-Gug (FXR antagonist) group, and HFD+CDCA+Z-Gug group, with 8 animals in each group. During intervention for 8 weeks, body weight and 24-hour food intake were measured every week. At the 8th week, oral glucose tolerance test (OGTT) and intraperitoneal glucose tolerance test (IPGTT) were conducted. After the mice were sacrificed, the serum levels of GLu, TG, CHO, LDL-C and HDL-C were detected; the expression levels of GLP-1 and FXR in intestinal tissues were detected by immunofluorescence assay; and the mRNA levels of TNF-α, IL-6, IL-1β, Gcg and FXR were detected by RT-qPCR; the serum level of GLP-1 was detected by ELISA, and the proportion of intraepithelial lymphocytes (IELs) subsets and the expression of CD26/DPP4 were detected by flow cytometry. Results Compared with the control group, the HFD group had increased body weight, abnormal serum glucose and lipid metabolism, impaired oral glucose tolerance, and weakened secretion of gastrointestinal hormones (P < 0.05), enhanced FXR expression at mRNA and protein levels, declined Gcg mRNA level and GLP-1 secretion level (P < 0.05), increased mRNA levels of intestinal inflammatory factors TNF-α, IL-6 and IL-1β (P < 0.05), raised proportions of TCRαβ+ IELs, TCRαβ+CD8αα+ IELs, and TCRαβ+CD8αβ+ IELs but reduced proportion of TCRγδ+IELs, and increased total CD26/DPP4 expression in IELs (P < 0.05). Compared with the HFD group, HFD+CDCA treatment resulted in significantly increased body weight, impaired oral glucose tolerance, decreased secretion of gastrointestinal hormones, increased FXR mRNA and protein expression, and decreased Gcg mRNA expression and GLP-1 secretion (P < 0.05); decreased proportions of TCRαβ+ IELs, TCRαβ+CD8αα+ IELs and TCRααβ+CD8αβ+ IELs but increased proportion of TCRγδ+ cells in IELs, and increased expression of total CD26/DPP4 in IELs (P < 0.05), which were significantly improved after Z-Gug intervention (P < 0.05). Conclusion CDCA may inhibit the expression and secretion of GLP-1 in intestinal tissue by activating FXR, and reduce the secretion of GLP-1. At the same time, CDCA may inhibit the expression of related inflammatory factors, regulate the proportions of IELs subsets, up-regulate the expression level of CD26/DPP4, promote the degradation of GLP-1 and aggravate insulin resistance. [Key words] chenodeoxycholic acid , glucagon-like peptide-1, farnesoid X receptor , intraepithelial lymphocytes , CD26 ,

Acute respiratory distress syndrome (ARDS) is characterized by dysregulated inflammation and increased permeability of lung microvascular cells. CD26/dipeptidyl peptidase-4 (DPP4) is a type II membrane protein that is expressed in several cell types and mediates multiple pleiotropic effects. We previously reported that DPP4 inhibition by sitagliptin attenuates lipopolysaccharide (LPS)-induced lung injury in mice. The current study characterized the functional role of CD26/DPP4 expression in LPS-induced lung injury in mice, isolated alveolar macrophages, and cultured lung endothelial cells. In LPS-induced lung injury, inflammatory responses [bronchoalveolar lavage fluid (BALF) neutrophil numbers and several proinflammatory cytokine levels] were attenuated in Dpp4 knockout (Dpp4 KO) mice. However, multiple assays of alveolar capillary permeability were similar between the Dpp4 KO and wild-type mice. TNF-α and IL-6 production was suppressed in alveolar macrophages isolated from Dpp4 KO mice. In contrast, in cultured mouse lung microvascular endothelial cells (MLMVECs), reduction in CD26/DPP4 expression by siRNA resulted in greater ICAM-1 and IL-6 expression after LPS stimulation. Moreover, the LPS-induced vascular monolayer permeability in vitro was higher in MLMVECs treated with Dpp4 siRNA, suggesting that CD26/DPP4 plays a protective role in endothelial barrier function. In summary, this study demonstrated that genetic deficiency of Dpp4 attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential functional roles of CD26/DPP4 expression in resident cellular components of the lung. CD26/DPP4 may be a potential therapeutic target for ARDS and warrants further exploration to precisely identify the multiple functional effects of CD26/DPP4 in ARDS pathophysiology. NEW & NOTEWORTHY: We aimed to clarify the functional roles of CD26/DPP4 in ARDS pathophysiology using Dpp4-deficient mice and siRNA reduction techniques in cultured lung cells. Our results suggest that CD26/DPP4 expression plays a proinflammatory role in alveolar macrophages while also playing a protective role in the endothelial barrier. Dpp4 genetic deficiency attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential roles of CD26/DPP4 expression in the resident cellular components of the lung. [ABSTRACT FROM AUTHOR]

Pulmonary hypertension (PH) with interstitial lung diseases (ILDs) often causes intractable conditions. CD26/Dipeptidyl peptidase-4 (DPP4) is expressed in lung constituent cells and may be related to the pathogenesis of various respiratory diseases. We aimed to clarify the functional roles of CD26/DPP4 in PH-ILD, paying particular attention to vascular smooth muscle cells (SMCs). Dpp4 knockout (Dpp4KO) and wild type (WT) mice were administered bleomycin (BLM) intraperitoneally to establish a PH-ILD model. The BLM-induced increase in the right ventricular systolic pressure and the right ventricular hypertrophy observed in WT mice were attenuated in Dpp4KO mice. The BLM-induced vascular muscularization in small pulmonary vessels in Dpp4KO mice was milder than that in WT mice. The viability of TGFβ-stimulated human pulmonary artery SMCs (hPASMCs) was lowered due to the DPP4 knockdown with small interfering RNA. According to the results of the transcriptome analysis, upregulated genes in hPASMCs with TGFβ treatment were related to pulmonary vascular SMC proliferation via the Notch, PI3K-Akt, and NFκB signaling pathways. Additionally, DPP4 knockdown in hPASMCs inhibited the pathways upregulated by TGFβ treatment. These results suggest that genetic deficiency of Dpp4 protects against BLM-induced PH-ILD by alleviating vascular remodeling, potentially through the exertion of an antiproliferative effect via inhibition of the TGFβ-related pathways in PASMCs. [ABSTRACT FROM AUTHOR]

The Middle East respiratory syndrome (MERS) is a severe respiratory disease with high fatality rates, caused by the Middle East respiratory syndrome coronavirus (MERS-CoV). The virus initiates infection by binding to the CD26 receptor (also known as dipeptidyl peptidase 4 or DPP4) via its spike protein. Although the receptor-binding domain (RBD) of the viral spike protein and the complex between RBD and the extracellular domain of CD26 have been studied using X-ray crystallography, conflicting studies exist regarding the importance of certain amino acids outside the resolved RBD-CD26 complex interaction interface. To gain atomic-level knowledge of the RBD-CD26 complex, we employed computational simulations to study the complex's dynamic behavior as it evolves from its crystal structure to a conformation stable in solution. Our study revealed previously unidentified interaction regions and interacting amino acids within the complex, determined a novel comprehensive RBD-binding domain of CD26, and by that expanded the current understanding of its structure. Additionally, we examined the impact of a single amino acid substitution, E513A, on the complex's stability. We discovered that this substitution disrupts the complex through an allosteric domino-like mechanism that affects other residues. Since MERS-CoV is a zoonotic virus, we evaluated its potential risk of human infection via animals, and suggest a low likelihood for possible infection by cats or dogs. The molecular structural information gleaned from our insights into the RBD-CD26 complex pre-dissociative states may be proved useful not only from a mechanistic view but also in assessing inter-species transmission and in developing anti-MERS-CoV antiviral therapeutics.

Cluster of differentiation 26 (CD26)/dipeptidyl peptidase 4 (DPP4) is an exopeptidase that is expressed as a transmembrane protein in many organs but also present in a circulating soluble form. Beyond its enzymatic and costimulatory activity, CD26/DPP4 is involved in the pathogenesis of chronic fibrotic diseases across many organ types, such as liver cirrhosis, kidney fibrosis and lung fibrosis. Organ fibrosis is associated with a high morbidity and mortality, and there are no causative therapies that can effectively attenuate the progress of the disease. Growing evidence suggests that inhibiting CD26/DPP4 can modulate the profibrotic tissue microenvironment and thus reduce fibrotic changes within affected organs. This review summarizes the role of CD26/DPP4 in fibroproliferative disorders and highlights new opportunities for an antifibrotic treatment by CD26/DPP4 inhibition. As a major advantage, CD26/DPP4 inhibitors have been in safe and routine clinical use in type 2 diabetes for many years and thus qualify for repurposing to repurpose as a promising therapeutic against fibrosis. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc [ABSTRACT FROM AUTHOR]

Abstract Background Nivolumab is an anti-PD1 antibody that has dramatically improved metastatic melanoma patients’ outcomes. Nevertheless, many patients are resistant to PD-1 inhibition, occasionally experiencing severe off-target immune toxicity. In addition, no robust and reproducible biomarkers have yet been validated to identify the correct selection of patients who will benefit from anti-PD-1 treatment avoiding unwanted side effects. However, the strength of CD26 expression on CD4+ T lymphocytes permits the characterization of three subtypes with variable degrees of responsiveness to tumors, suggesting that the presence of CD26-expressing T cells in patients might be a marker of responsiveness to PD-1-based therapies. Methods The frequency distribution of peripheral blood CD26-expressing cells was investigated employing multi-parametric flow cytometry in 69 metastatic melanoma patients along with clinical characteristics and blood count parameters at baseline (W0) and compared to 20 age- and sex-matched healthy controls. Percentages of baseline CD4+CD26high T cells were correlated with the outcome after nivolumab treatment. In addition, the frequency of CD4+CD26high T cells at W0 was compared with those obtained after 12 weeks (W1) of therapy in a sub-cohort of 33 patients. Results Circulating CD4+CD26high T cells were significantly reduced in melanoma patients compared to healthy subjects (p = 0.001). In addition, a significant association was observed between a low baseline percentage of CD4+CD26high T cells (

The association between immunoregulatory cytokines, such as interleukin (IL)‐10 or IL‐35, and dipeptidyl peptidase‐4 inhibitor (DPP4i)‐related bullous pemphigoid (BP) has not been evaluated. Serum IL‐10 and IL‐35 levels were measured in 39 patients with BP (24 males and 15 females; 6 DPP4i‐related and 33 DPP4i‐unrelated BP patients) and 10 healthy controls. The number of CD26+ cells in the dermis around bulla on sections was counted immunohistochemically for 12 patients (six patients with DPP4i‐related BP and six randomly sampled patients with DPP4i‐unrelated BP). Patients with DPP4i‐related BP had lower levels of serum eosinophils (DPP4i‐related vs. DPP4i‐unrelated BP: 476.1 ± 234.0 vs. 911.3 ± 948.8/μL; p = 0.537) and a higher rate of infiltrating CD26+ cells (32.9 ± 7.1% vs. 15.7 ± 4.4%; p = 0.01). There were no significant differences in serum IL‐10 (6.77 ± 0.24 vs. 6.84 ± 0.20 pg/mL), serum IL‐35 (2.63 ± 0.17 vs. 2.63 ± 0.21 pg/mL), serum anti‐BP180NC16a antibodies (67.31 ± 37.4 vs. 76.18 ± 54.59 U/mL) and Bullous Pemphigoid Disease Area Index before treatment in this study. Serum IL‐10 and IL‐35 levels do not increase in patients with BP and may not be a candidate for a therapeutic target for BP. An increase in CD26+ cells might be associated with DPP4i‐related BP. [ABSTRACT FROM AUTHOR]

Simple Summary: The monitoring of the minimal residual disease (MRD) in Chronic Myeloid Leukemia is a key element in the management of affected patients because it reflects the response to therapy and allows for the selection of the best responders who may benefit from the suspension of the therapy. The gold-standard method of MRD monitoring is the quantification of the BCR::ABL1 transcript, the hallmark of the disease, by RT-qPCR. Considering that almost half of the patients who discontinue the treatment experience a molecular relapse, the identification of new approaches for the improvement of the selection of the best-responding CML patients is needed. In the present pilot study, we compared the gold standard with two additional MRD techniques: the quantification of the BCR::ABL1 transcript by digital PCR and the quantification of leukemic stem cells by flowcytometry. In fact, this cell population is one of the factors driving relapses. Although no linear regression was observed, a correlation between the lowest levels obtained using the three methods was noted. To the best of our knowledge, this is the first time that these methods have been compared in the CML setting. A Deep Molecular Response (DMR), defined as a BCR::ABL1 transcript at levels ≤ 0.01% by RT-qPCR, is the prerequisite for the successful interruption of treatment among patients with Chronic Myeloid Leukemia (CML). However, approximately 50% of patients in Treatment-Free Remission (TFR) studies had to resume therapy after their BCR::ABL1 transcript levels rose above the 0.1% threshold. To improve transcript detection sensitivity and accuracy, transcript levels can be analyzed using digital PCR (dPCR). dPCR increases BCR::ABL1 transcript detection sensitivity 10–100 fold; however, its ability to better select successful TFR patients remains unclear. Beyond the role of the immune system, relapses may be due to the presence of residual leukemic stem cells (LSCs) that are transcriptionally silent. Flow cytometry can be used to identify and quantify circulating bone marrow Ph+ LSCs CD34+/CD38− co-expressing CD26 (dipeptidylpeptidase-IV). To date, the significance of circulating Ph+ LSCs in TFR is unclear. The aim of this work is to compare and examine the values obtained using the three different methods of detecting minimal residual disease (MRD) in CML at RNA (RT-qPCR and dPCR) and LSC (flowcytometry) levels among patients in TFR or exhibiting a DMR. The twenty-seven patients enrolled received treatment with either imatinib (12), dasatinib (6), nilotinib (7), bosutinib (1), or interferon (1). Twelve patients were in TFR, while the rest exhibited a DMR. The TFR patients had stopped therapy for less than 1 year (3), <3 years (2), 6 years (6), and 17 years (1). Blood samples were collected and tested using the three methods at the same time. Both d-PCR and LSCs showed higher sensitivity than RT-qPCR, exhibiting positive results in samples that were undetectable using RT-qPCR (17/27). None of the patients tested negative with d-PCR; however, 23/27 were under the threshold of 0.468 copies/μL, corresponding to a stable DMR. The results were divided into quartiles, and the lowest quartiles defined the lowest MRD. These data were strongly correlated in 15/27 patients, corresponding to almost half of the TFR patients. Indeed, the TFR patients, some lasting up to 17 years, corresponded to the lowest detectable DMR categories. To the best of our knowledge, this is the first attempt to analyze and compare DMRs in a CML population using standard (RT-qPCR) and highly sensitive (dPCR and LSCs) methods. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

cute myeloid leukemia (AML) is a devastating blood cancer with poor prognosis. Novel effective treatment is an urgent unmet need. Immunotherapy targeting T cell exhaustion by blocking inhibitory pathways, such as PD-1, is promising in cancer treatment. However, results from clinical studies applying PD-1 blockade to AML patients are largely disappointing. AML is highly heterogeneous. Identification of additional immune regulatory pathways and defining predictive biomarkers for treatment response are crucial to optimize the strategy. CD26 is a marker of T cell activation and involved in multiple immune processes. Here, we performed comprehensive phenotypic and functional analyses on the blood samples collected from AML patients and discovered that CD26lowPD-1+ CD8 T cells were associated with AML progression. Specifically, the percentage of this cell fraction was significantly higher in patients with newly diagnosed AML compared to that in patients achieved completed remission or healthy controls. Our subsequent studies on CD26lowPD-1+ CD8 T cells from AML patients at initial diagnosis demonstrated that this cell population highly expressed inhibitory receptors and displayed impaired cytokine production, indicating an exhaustion status. Importantly, CD26lowPD-1+ CD8 T cells carried features of terminal exhaustion, manifested by higher frequency of TEMRA differentiation, increased expression of transcription factors that are observed in terminally exhausted T cells, and high level of intracellular expression of granzyme B and perforin. Our findings suggest a prognostic and predictive value of CD26 in AML, providing pivotal information to optimize the immunotherapy for this devastating cancer. [ABSTRACT FROM AUTHOR]

The capacity of adipose stem/progenitor cells (ASCs) to undergo self-renewal and differentiation is crucial for adipose tissue homoeostasis, regeneration and expansion. However, the heterogeneous ASC populations of the adipose lineage constituting adipose tissue are not precisely known. In the present study, we demonstrate that cell surface expression of dipeptidyl peptidase-4 (DPP4)/cluster of differentiation 26 (CD26) subdivides the DLK1−/CD34+/CD45−/CD31− ASC pool of human white adipose tissues (WATs) into two large populations. Ex vivo, DPP4+ ASCs possess higher self-renewal and proliferation capacity and lesser adipocyte differentiation potential than DDP4− ASCs. The knock-down of DPP4 in ASC leads to significantly reduced proliferation and self-renewal capacity, while adipogenic differentiation is increased. Ectopic overexpression of DPP4 strongly inhibits adipogenesis. Moreover, in whole mount stainings of human subcutaneous (s)WAT, we detect DPP4 in CD34+ ASC located in the vascular stroma surrounding small blood vessels and in mature adipocytes. We conclude that DPP4 is a functional marker for an abundant ASC population in human WAT with high proliferation and self-renewal potential and low adipogenic differentiation capacity.

Objective To investigate the histological differences and expression of E-cadherin, Vimentin, matrix metalloprotein-9 (MMP-9), TNF-α, dipeptidyl-peptidase 4 (DPP4, also called CD26) in the margin and center of hypertrophic scar, superficial dilated keloid and normal skin. Methods Ten patients with keloid and another 10 with hypertrophic scar undergoing excision surgery in our hospital from October 2020 to August 2021 were included, and 8 cases requiring partial normal skin resection were also recruited. The resected tissues were collected, the tissue morphology was observed with HE staining, and the expression levels of E-cadherin, Vimentin, MMP-9, TNF-α and CD26 were detected by immunohistochemical staining and Western blotting. Results The E-cadherin expression in the epidermis of both keloid and hypertrophic scar was significantly lower than that of normal skin (P < 0.05), and the level in the edge of keloid was obviously weakened as compared with that of the center (P < 0.05), but there was no significant difference between the edge of hypertrophic scar and the center (P>0.05). By contrast, the expression levels of Vimentin, MMP-9, TNF-α and CD26 in the epidermis of both keloid and hypertrophic scar were remarkably enhanced when compared with those of normal skin (P < 0.05), and the keloids' edge higher than the center (P < 0.05), while no significance between the hypertrophic scars' edge and center (P>0.05). Conclusion The differences in epithelial-to-mesenchymal transition (EMT) and expression of relevant biomarkers within individual scars may be one of the reasons for the diversity of clinical features between hypertrophic scar and keloid, in which TNF-α and CD26 may be the key factors.

Background: Middle East respiratory syndrome-coronavirus (MERS-CoV) utilizes CD26 (dipeptidyl peptidase‐4) and CD66e or CEACAM5 (carcinoembryonic antigen-related cell adhesion molecule 5) receptors for cell infection. Peripheral blood mononuclear cells (PBMCs) play a critical role in mounting adaptive immune response against the virus. This study was performed to assess the expression of CD26 and CD66e on PBMCs and their susceptibility to MERS-CoV infection. Methods: Surface expression of CD26 and CD66e receptors on PBMCs from MERS-CoV patients (n = 20) and healthy controls (n = 20) was assessed by flow cytometry and the soluble forms were determined by enzyme-linked immunosorbent assay (ELISA). MERS-CoV UpE and Orf1a genes in PBMCs were detected by using Altona diagnostics reverse transcription polymerase chain reaction (RT-PCR) kit. Results: Mean fluorescent intensity (MFI) of CD66e was significantly higher on CD4 + lymphocytes (462.4 ± 64.35 vs 325.1 ± 19.69; p

Chemokines are a group of cytokines involved in the mobilization of leukocytes, which play a role in host defense and a variety of pathological conditions, including cancer. Interferon (IFN)-inducible chemokines C-X-C motif ligand 9 (CXCL), CXCL10, and CXCL11 are anti-tumor chemokines; however, the differential anti-tumor effects of IFN-inducible chemokines are not completely understood. In this study, we investigated the anti-tumor effects of IFN-inducible chemokines by transferring chemokine expression vectors into a mouse squamous cell carcinoma cell line, SCCVII, to generate a cell line stably expressing chemokines and transplanted it into nude mice. The results showed that CXCL9- and CXCL11-expressing cells markedly inhibited tumor growth, whereas CXCL10-expressing cells did not inhibit growth. The NH2-terminal amino acid sequence of mouse CXCL10 contains a cleavage sequence by dipeptidyl peptidase 4 (DPP4), an enzyme that cleaves the peptide chain of chemokines. IHC staining indicated DPP4 expression in the stromal tissue, suggesting CXCL10 inactivation. These results suggest that the anti-tumor effects of IFN-inducible chemokines are affected by the expression of chemokine-cleaving enzymes in tumor tissues. [ABSTRACT FROM AUTHOR]

Background: Nivolumab is an anti-PD1 antibody that has dramatically improved metastatic melanoma patients' outcomes. Nevertheless, many patients are resistant to PD-1 inhibition, occasionally experiencing severe off-target immune toxicity. In addition, no robust and reproducible biomarkers have yet been validated to identify the correct selection of patients who will benefit from anti-PD-1 treatment avoiding unwanted side effects. However, the strength of CD26 expression on CD4+ T lymphocytes permits the characterization of three subtypes with variable degrees of responsiveness to tumors, suggesting that the presence of CD26-expressing T cells in patients might be a marker of responsiveness to PD-1-based therapies. Methods: The frequency distribution of peripheral blood CD26-expressing cells was investigated employing multi-parametric flow cytometry in 69 metastatic melanoma patients along with clinical characteristics and blood count parameters at baseline (W0) and compared to 20 age- and sex-matched healthy controls. Percentages of baseline CD4+CD26high T cells were correlated with the outcome after nivolumab treatment. In addition, the frequency of CD4+CD26high T cells at W0 was compared with those obtained after 12 weeks (W1) of therapy in a sub-cohort of 33 patients. Results: Circulating CD4+CD26high T cells were significantly reduced in melanoma patients compared to healthy subjects (p = 0.001). In addition, a significant association was observed between a low baseline percentage of CD4+CD26high T cells (< 7.3%) and clinical outcomes, measured as overall survival (p = 0.010) and progression-free survival (p = 0.014). Moreover, patients with clinical benefit from nivolumab therapy had significantly higher frequencies of circulating CD4+CD26high T cells than patients with non-clinical benefit (p = 0.004) at 12 months. Also, a higher pre-treatment proportion of circulating CD4+CD26high T cells was correlated with Disease Control Rate (p = 0.014) and best Overall Response Rate (p = 0.009) at 12 months. Interestingly, after 12 weeks (W1) of nivolumab treatment, percentages of CD4+CD26high T cells were significantly higher in comparison with the frequencies measured at W0 (p < 0.0001), aligning the cell counts with the ranges seen in the blood of healthy subjects. Conclusions: Our study firstly demonstrates that peripheral blood circulating CD4+CD26high T lymphocytes represent potential biomarkers whose perturbations are associated with reduced survival and worse clinical outcomes in melanoma patients. [ABSTRACT FROM AUTHOR]

Ju Yup Lee,1,2 Mae-Ja Park3 1Department of Internal Medicine, Keimyung University School of Medicine, Daegu, South Korea; 2Institute for Cancer Research, Keimyung University, Daegu, South Korea; 3Department of Anatomy, School of Medicine, Kyungpook National University, Daegu, South KoreaCorrespondence: Mae-Ja Park, Department of Anatomy, School of Medicine, Kyungpook National University, Daegu, South Korea, Tel/Fax +82-53-420-4802, Email mjpark@knu.ac.krPurpose: The value of serum cluster of differentiation 26 (CD26) in gastric cancer remains unknown. We investigated serum CD26 as a non-invasive serological marker for the diagnosis of gastric cancer and its relationship with serum human epidermal growth factor receptor-2 (HER2) levels.Patients and Methods: We enrolled 393 gastric cancer patients treated with endoscopic resection or surgery, and 90 healthy controls. HER2 positivity in tissue was evaluated by immunohistochemistry staining, and the serum CD26 and HER2 levels were measured using an enzyme-linked immunosorbent assay.Results: Serum CD26 levels were significantly lower in gastric cancer patients than in healthy controls (582.2 ± 254.3 vs 862.7 ± 410.6 ng/mL, P< 0.001). Serum CD26 levels were significantly lower in advanced gastric cancer compared to early gastric cancer (642.2 ± 333.9 vs 503.4 ± 332.7 ng/mL, P< 0.001), and tended to decrease with gastric cancer progression. To diagnose gastric cancer, the optimal cut-off value of serum CD26 was 762.7 ng/mL with 75.6% sensitivity and 64.4% specificity. Serum CD26 levels were weakly correlated with serum HER2 levels (rs=0.363, P< 0.001). However, no difference in serum CD26 levels was observed between tissue HER2-negative and HER2-positive gastric cancer groups (586.2 ± 362.1 vs 579.6 ± 264.8 ng/mL, P=0.898).Conclusion: CD26 is a useful non-invasive serological marker for gastric cancer diagnosis; however, its levels do not correlate with HER2 status.Keywords: gastric cancer, biomarker, CD26, HER2

Abstract Introduction Human mesenchymal stromal cells (MSCs) have immunomodulatory, anti-inflammatory, and tolerogenic effects. Long-term in vitro expansion of MSCs to generate clinical grade products results in the accumulation of senescent-functionally impaired MSCs. Markers to assess the ‘senescent load’ of MSC products are needed. Methods Early and late passage human adipose tissue (AT) MSCs from pediatric and adult donors were characterized using established senescent markers [i.e., MSC size, granularity, and autofluorescence by flow cytometry; β-galactosidase staining (SA-β-gal); CDKN2A and CDKN1A by qRT-PCR]. In gene set enrichment analysis, DPP4 (also known as adenosine deaminase complexing protein 2 or CD26) was found as a prominent dysregulated transcript that was increased in late passage MSC(AT). This was confirmed in a larger number of MSC samples by PCR, flow cytometry, Western blotting, and immunofluorescence. In vitro immunopotency assays compared the function of CD26high and CD26low MSC(AT). The effect of senolytics on the CD26high subpopulation was evaluated in senescent MSC(AT). Results Late passage MSC(AT) had a senescence transcriptome signature. DPP4 was the most differentially enriched gene in senescent MSCs. Late passage senescent MSC(AT) had higher CD26 surface levels and total protein abundance. Moreover, CD26 surface levels were higher in early passage MSC(AT) from adults compared to pediatric donors. CD26 abundance correlated with established senescence markers. CD26high MSC(AT) had reduced immunopotency compared to CD26low MSC(AT). Senolytic treatment induced MSC apoptosis, which decreased the frequencies of CD26high MSC(AT). Conclusions DPP4 gene expression and DPP4/CD26 protein abundance are markers of replicative senescence in MSC(AT). Samples enriched in CD26high MSC(AT) have reduced immunopotency and CD26high MSCs are reduced with senolytics.

Acute myeloid leukemia (AML) is a devastating blood cancer with poor prognosis. Novel effective treatment is an urgent unmet need. Immunotherapy targeting T cell exhaustion by blocking inhibitory pathways, such as PD-1, is promising in cancer treatment. However, results from clinical studies applying PD-1 blockade to AML patients are largely disappointing. AML is highly heterogeneous. Identification of additional immune regulatory pathways and defining predictive biomarkers for treatment response are crucial to optimize the strategy. CD26 is a marker of T cell activation and involved in multiple immune processes. Here, we performed comprehensive phenotypic and functional analyses on the blood samples collected from AML patients and discovered that CD26lowPD-1+ CD8 T cells were associated with AML progression. Specifically, the percentage of this cell fraction was significantly higher in patients with newly diagnosed AML compared to that in patients achieved completed remission or healthy controls. Our subsequent studies on CD26lowPD-1+ CD8 T cells from AML patients at initial diagnosis demonstrated that this cell population highly expressed inhibitory receptors and displayed impaired cytokine production, indicating an exhaustion status. Importantly, CD26lowPD-1+ CD8 T cells carried features of terminal exhaustion, manifested by higher frequency of TEMRA differentiation, increased expression of transcription factors that are observed in terminally exhausted T cells, and high level of intracellular expression of granzyme B and perforin. Our findings suggest a prognostic and predictive value of CD26 in AML, providing pivotal information to optimize the immunotherapy for this devastating cancer.

The pathogenesis of pulmonary fibrosis involves complex interplay between cell types and signaling pathways. Recurrent alveolar epithelial injury can occur during pulmonary inflammation, causing dysregulation of epithelial repair. Dysregulated repair interacts with mesenchymal, inflammatory, and endothelial cells to trigger fibroblast‐to‐myofibroblast activation. CD26/dipeptidyl peptidase‐4 (DPP4) is a type II membrane protein mediating pleiotropic effect. However, the mechanistic role of CD26/DPP4 in pulmonary fibrosis remains unclear. In this study, we aimed to characterize Dpp4 deficiency in a mouse bleomycin (BLM)‐induced pulmonary fibrosis model and in cell culture systems of human lung fibroblasts (HLFs). Dpp4 knockout (Dpp4 KO) mouse lungs exhibited lower Ashcroft scale indices, collagen content, and numbers of fibroblasts and myofibroblasts compared with those in C57BL/6 wild‐type (WT) mice. Upregulation of Tgfb1 and Tgfb2 mRNA levels in the lungs after BLM treatment was lower in Dpp4 KO mice compared with those in WT mice. Although TGF‐β‐driven endothelial‐to‐mesenchymal transition (EndMT) has been implicated as one of the mechanisms of pulmonary fibrosis, a number of partial EndMT cells in lungs did not differ between Dpp4 KO mice and WT mice. The proliferation capacity and mRNA levels of COL1A1, a collagen deposition‐related gene, in cultured HLFs were suppressed in DPP4 small interfering RNA‐treated cells. This study indicates that the genetic deficiency of DPP4 has protective effects against BLM‐induced pulmonary fibrosis, partly through the reduction in TGF‐β expression and inhibition of fibroblast activation in the lung. Our study suggests that CD26/DPP4 inhibition is a potential therapeutic strategy for pulmonary fibrosis. [ABSTRACT FROM AUTHOR]

We evaluated the number of CD26 expressing cells in peripheral blood of patients with COVID‐19 within 72 h of admission and on day 4 and day 7 after enrollment. The majority of CD26 expressing cells were presented by CD3+CD4+ lymphocytes. A low number of CD26 expressing cells were found to be associated with critical‐severity COVID‐19 disease. Conversely, increasing numbers of CD26 expressing T cells over the first week of standard treatment was associated with good outcomes. Clinically, the number of circulating CD26 cells might be a marker of recovery or the therapeutic efficacy of anti‐COVID‐19 treatment. New therapies aimed at preserving and increasing the level of CD26 expressing T cells may prove useful in the treatment of COVID‐19 disease. [ABSTRACT FROM AUTHOR]

Abstract The pathogenesis of pulmonary fibrosis involves complex interplay between cell types and signaling pathways. Recurrent alveolar epithelial injury can occur during pulmonary inflammation, causing dysregulation of epithelial repair. Dysregulated repair interacts with mesenchymal, inflammatory, and endothelial cells to trigger fibroblast‐to‐myofibroblast activation. CD26/dipeptidyl peptidase‐4 (DPP4) is a type II membrane protein mediating pleiotropic effect. However, the mechanistic role of CD26/DPP4 in pulmonary fibrosis remains unclear. In this study, we aimed to characterize Dpp4 deficiency in a mouse bleomycin (BLM)‐induced pulmonary fibrosis model and in cell culture systems of human lung fibroblasts (HLFs). Dpp4 knockout (Dpp4 KO) mouse lungs exhibited lower Ashcroft scale indices, collagen content, and numbers of fibroblasts and myofibroblasts compared with those in C57BL/6 wild‐type (WT) mice. Upregulation of Tgfb1 and Tgfb2 mRNA levels in the lungs after BLM treatment was lower in Dpp4 KO mice compared with those in WT mice. Although TGF‐β‐driven endothelial‐to‐mesenchymal transition (EndMT) has been implicated as one of the mechanisms of pulmonary fibrosis, a number of partial EndMT cells in lungs did not differ between Dpp4 KO mice and WT mice. The proliferation capacity and mRNA levels of COL1A1, a collagen deposition‐related gene, in cultured HLFs were suppressed in DPP4 small interfering RNA‐treated cells. This study indicates that the genetic deficiency of DPP4 has protective effects against BLM‐induced pulmonary fibrosis, partly through the reduction in TGF‐β expression and inhibition of fibroblast activation in the lung. Our study suggests that CD26/DPP4 inhibition is a potential therapeutic strategy for pulmonary fibrosis.

Dipeptidyl-peptidase 4 (DPP4) is a multifunctional type II transmembrane glycoprotein that is expressed on various cell surfaces. While DPP4 inhibitors have a therapeutic role in the treatment of diabetes mellitus, they are an independent risk factor in the development of bullous pemphigoid. Contrarily, there are reports of improvement in psoriasis with DPP4 inhibition. We investigated the effect of DPP4 inhibition on primary human keratinocytes to determine whether DPP4 modulates keratinocyte inflammatory signaling and keratinocyte homeostasis. We performed RNA sequencing of primary adult human keratinocytes treated with DPP4 inhibitor, identifying 424 differentially expressed genes. Gene ontology analysis revealed significant enrichment of epidermal differentiation and cornified envelope genes. Using three-dimensional organotypic cultures and a pan-late cornified envelope 2 (LCE2) antibody, we demonstrate a dose dependent relationship between DPP4 inhibition and increased expression of LCE2 during epidermal development. The late cornified envelope gene clusters are expressed at the late stages of epithelial development, responding to stimuli such as calcium and ultraviolet light. While its biologic function is not fully understood, mutations in LCE3B/LCE3C confer a 40% increased risk in the development of plaque psoriasis. While we did not identify significant modulation of keratinocyte inflammatory markers, DPP4 inhibition increased expression of the late cornified envelope may offer a potential alternative therapeutic mechanism in psoriasis. [ABSTRACT FROM AUTHOR]

Middle East respiratory syndrome-coronavirus (MERS-CoV) utilizes CD26 (dipeptidyl peptidase‐4) and CD66e or CEACAM5 (carcinoembryonic antigen-related cell adhesion molecule 5) receptors for cell infection. Peripheral blood mononuclear cells (PBMCs) play a critical role in mounting adaptive immune response against the virus. This study was performed to assess the expression of CD26 and CD66e on PBMCs and their susceptibility to MERS-CoV infection. Surface expression of CD26 and CD66e receptors on PBMCs from MERS-CoV patients (n = 20) and healthy controls (n = 20) was assessed by flow cytometry and the soluble forms were determined by enzyme-linked immunosorbent assay (ELISA). MERS-CoV UpE and Orf1a genes in PBMCs were detected by using Altona diagnostics reverse transcription polymerase chain reaction (RT-PCR) kit. Mean fluorescent intensity (MFI) of CD66e was significantly higher on CD4 + lymphocytes (462.4 ± 64.35 vs 325.1 ± 19.69; p < 0.05) and CD8 + lymphocytes (533.8 ± 55.32 vs 392.4 ± 37.73; p < 0.04) from patients with MERS-CoV infection compared to the normal controls. No difference in MFI for CD66e was observed on monocytes (381.8 ± 40.34 vs 266.8 ± 20.6; p = 0.3) between the patients and controls. Soluble form of CD66e among MERS-CoV patients was also higher than the normal controls (mean= 338.7 ± 58.75 vs 160.7 ± 29.49 ng/mL; p < 0.01). Surface expression of CD26 on PBMCs and its soluble form were no different between the groups. MERS-CoV was detected by RT-PCR in 16/20 (80%) patients from whole blood, among them 8 patients were tested in PBMCs, 4/8 (50%) patients were positive. Increased expression levels of CD66e (CEACAM5) may contribute to increased susceptibility of PBMCs to MERS-CoV infection and disease progression. [ABSTRACT FROM AUTHOR]

Background: Angiotensin-converting enzyme 2 (ACE2) is known as the major viral entry site for SARS-CoV-2. However, viral tissue tropism and high rate of infectivity do not directly correspond with the level of ACE2 expression in the organs. It may suggest involvement of other receptors or accessory membrane proteins in SARSCoV-2 cell entry. Methods and Results: A systematic search was carried out in PubMed/Medline, EMBASE, and Cochrane Library for studies reporting SARS-CoV-2 cell entry. We used a group of the MeSH terms including "cell entry", "surface receptor", "ACE2", and "SARS-CoV-2". We reviewed all selected papers published in English up to end of February 2022. We found several receptors or auxiliary membrane proteins (including CD147, NRP-1, CD26, AGTR2, Band3, KREMEN1, ASGR1, ANP, TMEM30A, CLEC4G, and LDLRAD3) along with ACE2 that facilitate virus entry and transmission. Expression of Band3 protein on the surface of erythrocytes and evidence of binding with S protein of SARS-CoV-2 may explain asymptomatic hypoxemia during COVID19 infection. The variants of SARS-CoV-2 including the B.1.1.7 (Alpha), B.1.617.1 (Kappa), B.1.617.2 (Delta), B.1.617.2+ (Delta+), and B.1.1.529 (Omicron) may have different potency to bond with these receptors. Conclusions: The high rate of infectivity of SARS-CoV-2 may be due to its ability to enter the host cell through a group of cell surface receptors. These receptors are potential targets to develop novel therapeutic agents for SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Chronic lymphocytic leukemia (CLL) is most common in western countries forming about one-third of all leukemias in adults aged above 50 years. Some patients have indolent course and a survival very similar to the general population whereas others have a highly aggressive disease and a rapidly fatal outcome. CD49d and CD26 expressions have shown to independently predict prognosis in CLL. The study aimed to assess the expression of CD49d and CD26 in newly diagnosed CLL patients and find their correlation with clinical Binet stage, and other clinical parameters. Patients, materials and methods: This study was conducted on 51 newly diagnosed CLL patients based on lymphocyte count > 5×109/L and immunophenotyping. The expression of CD49d, and CD26 were investigated using eight-color flow cytometer. Results: The expression of CD49d and CD26 were detected in 56.9 %, 68.8 % of CLL patients, respectively. The correlation between CD49d expression and CD26 expression was statistically significant (p < 0.001) with high concordance rate between them. The positive expression of both CD49d and CD26 had statistically significant association with clinical Binet staging (p < 0.001, and 0.001, respectively) and their combined positive expression had also statistically significant association with clinical Binet stage of the disease (p < 0.001) with the highest combined positive rate was associated with stage C then followed by B in comparison with stage A. Conclusion: Positive CD49d and CD26 expressions were significantly correlated with advanced clinical Binet stage and associated with frequent lymphadenopathy and their combined positive expression had highly significant correlation with advanced clinical Binet stage and therefore their co expression could be beneficial as reliable prognostic indicator in CLL patients. [ABSTRACT FROM AUTHOR]

The advent of tyrosine kinase inhibitors (TKIs) as treatment of chronic myeloid leukemia (CML) is a paradigm in molecularly targeted cancer therapy. Nonetheless, TKI-insensitive leukemia stem cells (LSCs) persist in most patients even after years of treatment and are imperative for disease progression as well as recurrence during treatment-free remission (TFR). Here, we have generated high-resolution single-cell multiomics maps from CML patients at diagnosis, retrospectively stratified by BCR::ABL1 IS (%) following 12 months of TKI therapy. Simultaneous measurement of global gene expression profiles together with >40 surface markers from the same cells revealed that each patient harbored a unique composition of stem and progenitor cells at diagnosis. The patients with treatment failure after 12 months of therapy had a markedly higher abundance of molecularly defined primitive cells at diagnosis compared to the optimal responders. The multiomic feature landscape enabled visualization of the primitive fraction as a mixture of molecularly distinct BCR::ABL1 + LSCs and BCR::ABL1 - hematopoietic stem cells (HSCs) in variable ratio across patients, and guided their prospective isolation by a combination of CD26 and CD35 cell surface markers. We for the first time show that BCR::ABL1 + LSCs and BCR::ABL1 - HSCs can be distinctly separated as CD26 + CD35 - and CD26 - CD35 + , respectively. In addition, we found the ratio of LSC/HSC to be higher in patients with prospective treatment failure compared to optimal responders, at diagnosis as well as following 3 months of TKI therapy. Collectively, this data builds a framework for understanding therapy response and adapting treatment by devising strategies to extinguish or suppress TKI-insensitive LSCs., Competing Interests: RW, LG, FS, MS, SS, RT No competing interests declared, PD, GK Is a board member and has equity in Nygen Analytics AB, HH Received honoraria from Pfizer, Novartis, BMS, and Incyte, SM Received honoraria and research funding from BMS, research funding from Novartis, Janpix, and honoraria from Dren Bio, JR Received honoraria and research funding from Novartis and Bristol-Myers Squibb (BMS) and honoraria from Ariad, (© 2023, Warfvinge et al.)

A new approach helps examine the proportion of cancerous and healthy stem cells in patients with chronic myeloid leukemia and how this influences treatment outcomes., Competing Interests: NA, SE No competing interests declared, (© 2024, Arellano and Elf.)

Background: Asthma pathology may induce changes in naïve/memory lymphocyte proportions assessable through the evaluation of surface CD26 (dipeptidyl peptidase 4/DPP4) levels. Our aim was to investigate the association of asthma phenotype/severity with the relative frequency of CD26 -/lo , CD26 int and CD26 hi subsets within different lymphocyte populations., Methods: The proportion of CD26 -/lo , CD26 int and CD26 hi subsets within CD4 + effector T cells (T eff ), total CD4 - lymphocytes, γδ-T cells, NK cells and NKT cells was measured in peripheral blood samples from healthy (N = 30) and asthma (N = 119) donors with different phenotypes/severities by flow cytometry. We performed K-means clustering analysis and further characterised the CD4 + CD26 -/lo T eff cell subset by LC-MS/MS and immunofluorescence., Results: Cluster analysis including clinical and flow cytometry data resulted in four groups, two of them with opposite inflammatory profiles (neutrophilic vs. eosinophilic). Neutrophilic asthma presented reduced CD4 - CD26 hi cells, which negatively correlated with systemic inflammation. Eosinophilic asthma displayed a general expansion of CD26 -/lo subsets. Specifically, CD4 + CD26 -/lo T eff expansion was confirmed in asthma, especially in atopic patients. Proteomic characterisation of this subset with a T EM /T EMRA phenotype revealed upregulated levels of innate (e.g. MPO and RNASE2) and cytoskeleton/extracellular matrix (e.g. MMP9 and ACTN1) proteins. Immunofluorescence assays confirmed the presence of atypical proteins for CD4 + T cells, and an enrichment in 'flower-like' nuclei and MMP9/RNASE2 levels in CD4 + CD26 -/lo T eff compared to CD4 + T lymphocytes., Conclusion: There is an association between CD26 levels in different lymphocyte subsets and asthma phenotype/severity. CD4 + CD26 -/lo T EMRA cells expressing innate proteins specific to eosinophils/neutrophils could be determinant in sustaining long-term inflammation in adult allergic asthma., (© 2024 The Author(s). Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

Abstract Background Hereditary hemorrhagic telangiectasia (HHT) is a rare genetic disease characterized by a deregulated neo-angiogenesis. Besides a mainly vascular phenotype (muco-cutaneous telangiectases, arteriovenous malformations), a specific risk of infection is suggested by case series of severe and atypical infections as well as by reports of decreased T and natural killer (NK) lymphocyte counts. As some evidence supports a dysregulation of the CXCR4/CXCL12 chemotactic axis of HHT endothelial cells, we hypothesized that a similar phenomenon could occur on lymphocytes. Methods Eighteen HHT patients with history of severe infection (HSI) were matched in age and sex with 18 HHT without HSI and 18 healthy control subjects (HC). We assessed the cell count and the surface expression of CXCR4 and CD26 (CXCL12 inactivating peptidase) of circulating T-helper and T-cytotoxic lymphocytes (including naive, memory and activated subsets) and NK cells. Results The overall HHT group of 36 patients exhibited a reduction of circulating T-helper lymphocytes compared to HC (median: 517 vs. 1026 cells/mm3, p

In classical Hodgkin lymphoma (cHL), the highly abundant CD4+ T cells in the vicinity of tumor cells are considered essential for tumor cell survival, but are ill-defined. Although they are activated, they consistently lack expression of activation marker CD26. In this study, we compared sorted CD4+CD26- and CD4+CD26+ T cells from cHL lymph node cell suspensions by RNA sequencing and T cell receptor variable gene segment usage analysis. This revealed that although CD4+CD26- T cells are antigen experienced, they have not clonally expanded. This may well be explained by the expression of exhaustion associated transcription factors TOX and TOX2, immune checkpoints PDCD1 and CD200, and chemokine CXCL13, which were amongst the 100 significantly enriched genes in comparison with the CD4+CD26+ T cells. Findings were validated in single-cell RNA sequencing data from an independent cohort. Interestingly, immunohistochemistry revealed predominant and high frequency of staining for TOX and TOX2 in the T cells attached to the tumor cells. In conclusion, the dominant CD4+CD26- T cell population in cHL is antigen experienced, polyclonal, and exhausted. This population is likely a main contributor to the very high response rates to immune checkpoint inhibitors in cHL.

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.

DPP4/CD26 is a single-pass transmembrane protein with multiple functions on glycemic control, cell migration and proliferation, and the immune system, among others. It has recently acquired an especial relevance due to the possibility to act as a receptor or co-receptor for SARS-CoV-2, as it has been already demonstrated for other coronaviruses. In this review, we analyze the evidence for the role of DPP4 on COVID-19 risk and clinical outcome, and its contribution to COVID-19 physiopathology. Due to the pathogenetic links between COVID-19 and diabetes mellitus and the hyperinflammatory response, with the hallmark cytokine storm developed very often during the disease, we dive deep into the functions of DPP4 on carbohydrate metabolism and immune system regulation. We show that the broad spectrum of functions regulated by DPP4 is performed both as a protease enzyme, as well as an interacting partner of other molecules on the cell surface. In addition, we provide an update of the DPP4 inhibitors approved by the EMA and/or the FDA, together with the newfangled approval of generic drugs (in 2021 and 2022). This review will also cover the effects of DPP4 inhibitors (i.e., gliptins) on the progression of SARS-CoV-2 infection, showing the role of DPP4 in this disturbing disease. [ABSTRACT FROM AUTHOR]

Introduction: Human mesenchymal stromal cells (MSCs) have immunomodulatory, anti-inflammatory, and tolerogenic effects. Long-term in vitro expansion of MSCs to generate clinical grade products results in the accumulation of senescent-functionally impaired MSCs. Markers to assess the 'senescent load' of MSC products are needed. Methods: Early and late passage human adipose tissue (AT) MSCs from pediatric and adult donors were characterized using established senescent markers [i.e., MSC size, granularity, and autofluorescence by flow cytometry; β-galactosidase staining (SA-β-gal); CDKN2A and CDKN1A by qRT-PCR]. In gene set enrichment analysis, DPP4 (also known as adenosine deaminase complexing protein 2 or CD26) was found as a prominent dysregulated transcript that was increased in late passage MSC(AT). This was confirmed in a larger number of MSC samples by PCR, flow cytometry, Western blotting, and immunofluorescence. In vitro immunopotency assays compared the function of CD26high and CD26low MSC(AT). The effect of senolytics on the CD26high subpopulation was evaluated in senescent MSC(AT). Results: Late passage MSC(AT) had a senescence transcriptome signature. DPP4 was the most differentially enriched gene in senescent MSCs. Late passage senescent MSC(AT) had higher CD26 surface levels and total protein abundance. Moreover, CD26 surface levels were higher in early passage MSC(AT) from adults compared to pediatric donors. CD26 abundance correlated with established senescence markers. CD26high MSC(AT) had reduced immunopotency compared to CD26low MSC(AT). Senolytic treatment induced MSC apoptosis, which decreased the frequencies of CD26high MSC(AT). Conclusions: DPP4 gene expression and DPP4/CD26 protein abundance are markers of replicative senescence in MSC(AT). Samples enriched in CD26high MSC(AT) have reduced immunopotency and CD26high MSCs are reduced with senolytics. [ABSTRACT FROM AUTHOR]

Simple Summary: The cd26 gene is known to be significantly involved in immune responses. However, there are very few studies that have used cd26 siRNA in porcine embryos and no available information regarding its role during this pre-implantation development in in vitro. In the present study, the cd26 siRNA-injected oocytes showed significantly lower blastocyst development than control groups and we confirmed aberrant gene expression patterns of the porcine parthenogenetic embryo development. This study showed the possibility that the cd26 plays an important role in in vitro development of the porcine pre-implantation embryo. cd26 is ubiquitously distributed in the body, particularly in the endothelial and epithelial cells, with the highest expression in the kidney, liver, and small intestine. In humans, cd26 serves as a marker for the embryo implantation phase. However, little is known about the role of cd26 in porcine pre-implantation embryo development. Here, we aimed to examine siRNA-induced cd26 downregulation in the cytoplasm of MII oocytes, to determine whether cd26 is involved in the regulation of porcine pre-implantation embryonic development. The cd26 siRNA was micro-injected into the cytoplasm of MII oocytes, which were then parthenogenetically activated electrically in a medium containing 0.3M Mannitol. Inhibition of the cd26 expression did not affect cleavage but stopped development in the blastocyst stage. Additionally, the cd26 siRNA-treated blastocysts had significantly more apoptotic cells than the untreated blastocysts. Among the 579 transcripts evaluated with transcriptome resequencing, 38 genes were differentially expressed between the treatment and control blastocysts (p < 0.05). Twenty-four genes were upregulated in cd26 siRNA-injected blastocysts, whereas 14 were downregulated. These genes are involved in apoptosis, accumulation of reactive oxygen species, and aberrant expression of ribosomal protein genes. Our results indicate that cd26 is required for proper porcine parthenogenetic activation during embryonic development. [ABSTRACT FROM AUTHOR]

Background. Exosomes are microvesicles that actively participate in signaling mechanisms and depending on their content can contribute to the development of different pathologies, such as diabetes and cardiovascular disease. Objective. The aim of this study was to evaluate the association of cystatin C, CD26, and CD14 proteins in serum exosomes from patients with Type 2 Diabetes (T2D), metabolic syndrome (MetS), and atherogenic index of plasma (AIP). Methods. Serum exosomes were isolated by ultracentrifugation from 147 individuals with and without diabetes. Both anthropometric and metabolic parameters were registered from everyone. The levels of exosomal proteins cystatin C, CD26, and CD14 were quantified by ELISA. The association between protein levels and T2D or atherogenic risk factors was analyzed by linear regression and generalized regression models. Results. We observed a significant correlation of increased glucose with elevated levels of Cystatin C, and an effect of T2D on the levels of CD26 (βD45:8 pg/mg; pD0:001) and CD14 (βD168 pg/mg; p<0:001) compared to subjects without T2D. CD14 was significantly related to T2D, metabolic syndrome, glucose, and the Atherogenic Index of Plasma (AIP). Additionally, we observed a significant effect of metabolic syndrome MetS on the increase of exosomal Cystatin C and CD14. Conclusions. T2D may contribute to the increase of CD14 protein contained in exosomes, as well as to the predisposition of atherogenic events development due to its relationship with the increase in serum triglyceride concentrations and the AIP score. Finally, the increased levels of CD14 and Cystatin C in exosomes are related to MetS. The analysis of exosome contents of diabetic patients remains an incipient field, so extensive characterization is crucial for their use as biomarkers or to analyze their possible contribution to diabetic complications. [ABSTRACT FROM AUTHOR]

Background Exosomes are microvesicles that actively participate in signaling mechanisms and depending on their content can contribute to the development of different pathologies, such as diabetes and cardiovascular disease. Objective The aim of this study was to evaluate the association of cystatin C, CD26, and CD14 proteins in serum exosomes from patients with Type 2 Diabetes (T2D), metabolic syndrome (MetS), and atherogenic index of plasma (AIP). Methods Serum exosomes were isolated by ultracentrifugation from 147 individuals with and without diabetes. Both anthropometric and metabolic parameters were registered from everyone. The levels of exosomal proteins cystatin C, CD26, and CD14 were quantified by ELISA. The association between protein levels and T2D or atherogenic risk factors was analyzed by linear regression and generalized regression models. Results We observed a significant correlation of increased glucose with elevated levels of Cystatin C, and an effect of T2D on the levels of CD26 (β = 45.8 pg/µg; p = 0.001) and CD14 (β = 168 pg/µg; p

Cancer-associated fibroblasts (CAFs) are a heterogeneous population of fibroblasts with various features in the cancer stroma and have been reported to influence cancer progression through cell–cell interactions in various types of malignancies, including lung adenocarcinoma (LUAD). Dipeptidyl peptidase 4 (DPP4) is a transmembrane protein with serine protease activity and is involved in the progression of tumors, metabolic diseases, and autoimmune diseases. In the present study, we focused on the role of DPP4-positive CAFs in LUAD. Immunohistochemistry revealed that 38 of 89 LUAD patients showed DPP4 expression in the fibrous stroma, and patients harboring DPP4-positive CAFs were more often male, had a higher Brinkman index, and had a higher Ki-67 labeling index of tumor cells than those with DPP4-negative CAFs. DPP4-positivity was associated with the expression of other CAF markers, α-SMA, periostin, and podoplanin, as well as a cellular senescence marker, p16. In the in vitro study, conditioned media collected from pulmonary fibroblast (OUS-11, HPF, and HPF-C)-induced overexpression of DPP4 significantly promoted the proliferation of LUAD cells (A549 and PC-9) and increased the expression levels of MCP-1, IL-8, IL-6, and GCSF in the media compared to those in controls. In addition, OUS-11 overexpression in DPP4 overexpression increased periostin expression. In conclusion, DPP4-positive CAFs could promote lung adenocarcinoma cell growth by producing soluble factors, and DPP4 inhibition may inhibit cancer progression. • Lung adenocarcinoma cases with DPP4-positive CAFs showed high Ki-67 LI in cancer. • DPP4-immunopositivity was associated with other conventional CAF marker expressions. • DPP4-positive fibroblasts significantly increased lung adenocarcinoma cell growth. • DPP4 overexpression increased MCP-1, IL-8, IL-6, and GCSF in media of fibroblasts. • DPP4 overexpression increased periostin in pulmonary fibroblasts. [ABSTRACT FROM AUTHOR]

Background: Recently, CD26 have been identified as one of the promising and specific marker for the identification of leukemic stem cells (LSCs) in chronic myeloid leukemia (CML). Methods: This was a prospective, observational validation study. Peripheral blood (PB) samples from suspected cases of CML and other hematolymphoid neoplasm were evaluated for the expression of CD26 on stem cells (SC) (CD45 dim/CD34+/CD38‐) fraction by flow cytometry (FCM) using a single tube four‐color antibodies cocktail: CD45‐V500 /CD26‐PE/CD34‐PerCPcy5.5/CD38‐APC‐H7. The diagnosis of CML was confirmed using cytogenetics and/or molecular studies. Additionally, 12 paired PB and bone marrow (BM) samples of CML cases were compared for the proportion of CD26+ LSCs. Results: Expression of CD26 on the SC fraction was invariably noted in all cases (116/116) of CML, irrespective of the disease phase and transcript type. None of other neoplasm (0/26), including the Ph + ALLs expressed CD26. Proportion of SCs expressing CD26 was variable with a median (range) proportion being 61.3% (7.6%–98.6%). Evaluation of paired PB and BM samples showed similar proportion of CD26 + LSCs (R2: 0.969). Conclusion: We confirmed that FCM evaluation of CD26 expression in the PB LSCs is a rapid and specific tool for CML diagnosis. Its utility as a marker for residual disease evaluation can also be explored in the future. [ABSTRACT FROM AUTHOR]

Background: Chronic myeloid leukemia (CML) is a hematopoietic stem cell (SC) neoplasm diagnosed by the demonstration of t(9;22)(BCR‐ABL1) fusion gene. We performed a flow cytometric assay to identify CD26+ CML leukemic stem cells (LSCs) for its value as a standalone diagnostic investigation for CML and its utility for detection of residual disease in CML patients on therapy. Methods: Patients with clinical suspicion of CML/CML on follow‐up were included, and peripheral (PB) and/or bone marrow (BM) samples were utilized for flow cytometric analysis. PB and/or BM of patients with diseases other than CML were used as controls. A pre‐titrated antibody cocktail containing CD45, CD34, CD38, and CD26 MoABs was used. Results: A total of 104 samples (63 PB and 41 BM) from 64 patients [suspected CML (n = 30), CML on follow‐up (n = 15), and non‐CML (n = 19)] were tested. CD26+ LSCs were identified in all patients with a confirmed diagnosis of CML (median = 0.07 (range 0.002%–26.79%)). None of the patients in the control group (non‐CML) and follow‐up patients with negative reverse transcriptase‐polymerase chain reaction (RT‐PCR) results showed the presence of CD26+ LSCs. Also, there was a strong correlation between CD26+ CML LSCs in the PB and BM (r =.917). Conclusion: Flow cytometric identification of CD26+ LSCs in the peripheral blood can be a cheap, rapid, robust, and potential diagnostic tool for the diagnosis of CML compared to available testing methods. It is irrespective of BCR‐ABL1 transcript type, and its role in residual disease monitoring needs thorough investigation. [ABSTRACT FROM AUTHOR]

Jaquellyne Gurgel Penaforte-Saboia,1,2 Carlos Eduardo Barra Couri,3 Natasha Vasconcelos Albuquerque,1,4 Vanessa Lauanna Lima Silva,5 Natália Bitar da Cunha Olegario,1,2 Virgínia Oliveira Fernandes,1,2,4 Renan Magalhães Montenegro Junior1,2,4 1Clinical Research Unit, Walter Cantidio University Hospital, Federal University of Ceará, Fortaleza, Brazil; 2Department of Clinical Medicine, Federal University of Ceará, Fortaleza, Brazil; 3Center for Cell-Based Therapy, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil; 4Department of Community Health, Federal University of Ceará, Fortaleza, Brazil; 5Department of Clinical Medicine, Hospital and Maternity Dra Zilda Arns Neumann, Fortaleza, BrazilCorrespondence: Renan Magalhães Montenegro JuniorFederal University of Ceará, Rua Coronel Nunes de Melo s/n, Fortaleza, 60430-270, Ceará, BrazilTel +55 8533668600Fax +55 85 3366-8619Email renanmmjr@gmail.comAbstract: Type 1 diabetes mellitus (T1DM) results from the immune cell-mediated destruction of functional pancreatic β-cells. In the presymptomatic period, T1DM is characterized by the presence of two or more autoantibodies against the islet cells in patients without glycemic decompensation. Therapeutic strategies that can modify the autoimmune process could slow the progression of T1DM. Dipeptidyl peptidase-4 (DPP-4) or CD26, a multifunctional serine protease with a dual function (regulatory protease and binding protein), can modulate inflammation and immune cell-mediated β-cell destruction. CD26 is involved in T-cell co-stimulation, migration, memory development, thymic maturation, and emigration patterns. DPP-4 degrades the peptide hormones GLP-1 and GIP. In addition to regulating glucose metabolism, DPP-4 exerts anti-apoptotic, regenerative, and proliferative effects to promote β-cell mass expansion. GLP-1 receptor signaling may regulate murine lymphocyte proliferation and maintenance of peripheral regulatory T-cells. In patients with T1DM, the serum DPP-4 activity is upregulated. Several studies have suggested that the upregulated DPP-4 activity is correlated with T1DM pathophysiology. DPP-4, which is preferentially expressed on the Th1 surface, can promote the polarization of Th1 immunity, a prerequisite for T1DM development. CD26 inhibition can suppress T-cell proliferation and Th1 cytokine production and stimulate tumor growth factor beta-1 (TGF-β 1) secretion, which plays an important role in the regulation of autoimmunity in T1DM. Studies on humans or animal models of T1DM have suggested that DPP-4 inhibitors can improve β-cell function and attenuate autoimmunity in addition to decreasing insulin dependence. This review summarizes the emerging roles of DPP-4 inhibitors in potentially delaying the progression of T1DM.Keywords: CD26, type 1 diabetes mellitus, autoimmunity, autoantibodies, therapeutic targets, prevention