Implicit Flow Cytometric Diagnosis of Classic Hodgkin Lymphoma Using CD3+CD4+CD26- T-Cells.

BACKGROUND: Flow cytometry is not routinely performed in clinical laboratories for the diagnosis of classic Hodgkin lymphoma (CHL). METHODS: Fourteen cases of CHL and 132 cases of the control group were studied by 10-color flow cytometry, with markers including CD3, CD4, CD7, CD8, and CD26, as well as calculated parameters such as the CD4:CD8 ratio, percent CD3+CD4+CD26- T-cells of CD3+CD4+ T-cells, percent CD3+CD4+CD26- T-cells of total events, CD7 coefficient of variation among CD3+CD4+CD26- T-cells, and CD7 median fluorescence intensity of CD3+CD4+CD26- T-cells relative to CD3+CD8+ T-cells. RESULTS: CHL cases showed a median percent CD3+CD4+CD26- of CD3+CD4+ T-cells of 72.3% with range from 41.1% to 94.4%, median percent CD3+CD4+CD26- T-cells of total events of 17.4% with range from 4.6% to 52.5%, CD7 coefficient of variation among CD3+CD4+CD26- T-cells less than 100%, and CD7 median fluorescence intensity of CD3+CD4+CD26- T-cells relative to CD3+CD8+ T-cells of 1.7 with range from 0.4 to 3.5. In the control group, every entity showed some degree of overlap with CHL in terms of these parameters. A "Hodgkin score" was thus constructed to enhance separation of CHL from other entities. A threshold Hodgkin score of 15.35 achieved a sensitivity of 78.6% and specificity of 96.2% in the diagnosis of CHL. Incorporating the Hodgkin score into a simple algorithm raises the specificity to 100%. CONCLUSION: In this study, we used flow cytometry to demonstrate increased CD3+CD4+CD26- T-cells in CHL, and derived a Hodgkin score for the diagnosis of CHL.

Impact of inpatient management of hyperglycemia on peripheral T cell markers in patients with type 2 diabetes.

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. Supplementary Information: The online version contains supplementary material available at 10.1007/s13340-024-00697-7.

Could Flow Cytometry Provide New Prognostic Markers in Colorectal Cancer?

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.

Soluble CD26: From Suggested Biomarker for Cancer Diagnosis to Plausible Marker for Dynamic Monitoring of Immunotherapy.

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.

Molecular basis for receptor recognition and broad host tropism for merbecovirus MjHKU4r-CoV-1.

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.

ADA/CD26 axis increases intra-tumor PD-1+CD28+CD8+ T-cell fitness and affects NSCLC prognosis and response to ICB.

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.

Dipeptidyl peptidase 4-positive cancer-associated fibroblasts enhance lung adenocarcinoma growth.

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.

Peripheral blood quantitation of CD26 positive leukemic stem cells as a predictor of tyrosine kinase inhibitor response in chronic myeloid leukemia.

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.

Precise correction of a spectrum of ß-thalassemia mutations in coding and non-coding regions by base editors.

ß-thalassemia/HbE results from mutations in the ß-globin locus that impede the production of functional adult hemoglobin. Base editors (BEs) could facilitate the correction of the point mutations with minimal or no indel creation, but its efficiency and bystander editing for the correction of ß-thalassemia mutations in coding and non-coding regions remains unexplored. Here, we screened BE variants in HUDEP-2 cells for their ability to correct a spectrum of ß-thalassemia mutations that were integrated into the genome as fragments of HBB. The identified targets were introduced into their endogenous genomic location using BEs and Cas9/homology-directed repair (HDR) to create cellular models with ß-thalassemia/HbE. These ß-thalassemia/HbE models were then used to assess the efficiency of correction in the native locus and functional ß-globin restoration. Most bystander edits produced near target sites did not interfere with adult hemoglobin expression and are not predicted to be pathogenic. Further, the effectiveness of BE was validated for the correction of the pathogenic HbE variant in severe ß0/ßE-thalassaemia patient cells. Overall, our study establishes a novel platform to screen and select optimal BE tools for therapeutic genome editing by demonstrating the precise, efficient, and scarless correction of pathogenic point mutations spanning multiple regions of HBB including the promoter, intron, and exons.

Flow Cytometric Assessment of CD26-Positive Leukemic Stem Cells: A Rapid and Valuable Tool in the Diagnosis and Follow-Up of Chronic Myeloid Leukemia.

Context Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasm. Recent studies have suggested that CD26-positive leukemic stem cells (LSCs) circulating in peripheral blood are specific for CML. Objective This study was undertaken to determine the proportion of CD26-positive LSCs at diagnosis and its change during tyrosine kinase inhibitor therapy. Design This prospective study was conducted on 43 cases of CML at diagnosis. For flow cytometry, peripheral blood cells were stained with CD45, CD34, CD38, CD3, and CD26. A sequential gating strategy with CD45/SSC (side scatter), CD34/SSC, and CD34/CD38 was applied to identify CD45+/34+/38- populations, from which CD26-positive stem cells were identified and compared with controls. Data analysis was done with Kaluza software. Results All patients diagnosed with CML were detected with CD26-positive LSCs. The median percentage of CD26-positive CML LSCs was 0.02 with a range of 0.001 to 1.77. None of the control samples showed CD26 positivity. The percentage and absolute count of CD26-positive CML LSCs were reduced after six months of tyrosine kinase therapy in patients with complete hematological remission. Conclusion Flow cytometric analysis of circulating CD26-positive CML LSCs is a non-invasive, rapid, and useful tool in the diagnosis and follow-up of CML.

Selective refueling of CAR T cells using ADA1 and CD26 boosts antitumor immunity.

Chimeric antigen receptor (CAR) T cell therapy is hindered in solid tumor treatment due to the immunosuppressive tumor microenvironment and suboptimal T cell persistence. Current strategies do not address nutrient competition in the microenvironment. Hence, we present a metabolic refueling approach using inosine as an alternative fuel. CAR T cells were engineered to express membrane-bound CD26 and cytoplasmic adenosine deaminase 1 (ADA1), converting adenosine to inosine. Autocrine secretion of ADA1 upon CD3/CD26 stimulation activates CAR T cells, improving migration and resistance to transforming growth factor ß1 suppression. Fusion of ADA1 with anti-CD3 scFv further boosts inosine production and minimizes tumor cell feeding. In mouse models of hepatocellular carcinoma and non-small cell lung cancer, metabolically refueled CAR T cells exhibit superior tumor reduction compared to unmodified CAR T cells. Overall, our study highlights the potential of selective inosine refueling to enhance CAR T therapy efficacy against solid tumors.

Functional roles of CD26/DPP4 in lipopolysaccharide-induced lung injury.

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.

Functional Roles of CD26/DPP4 in Bleomycin-Induced Pulmonary Hypertension Associated with Interstitial Lung Disease.

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 TGFß-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 TGFß 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 TGFß 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 TGFß-related pathways in PASMCs.

Molecular insights on the coronavirus MERS-CoV interaction with the CD26 receptor.

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.

Favorable effect of CD26/DPP-4 inhibitors on postoperative outcomes after lung transplantation: A propensity-weighted analysis.

BACKGROUND: We have shown the efficacy of CD26/dipeptidyl peptidase 4 (CD26/DPP-4) inhibitors, antidiabetic agents, in allograft protection after experimental lung transplantation (LTx). We aimed to elucidate whether CD26/DPP-4 inhibitors effectively improve postoperative outcomes after clinical LTx. METHODS: We retrospectively reviewed the records of patients undergoing LTx at our institution between 2010 and 2021 and extracted records of patients with diabetes mellitus (DM) at 6 months post-LTx. The patient characteristics and postoperative outcomes were analyzed. We established 6 months post-LTx as the landmark point for predicting overall survival (OS) and chronic lung allograft dysfunction (CLAD)-free survival. Hazard ratios were estimated by Cox regression after propensity score weighting, using CD26/DPP-4 inhibitor treatment up to 6 months post-LTx as the exposure variable. We evaluated CLAD samples pathologically, including for CD26/DPP-4 immunohistochemistry. RESULTS: Of 102 LTx patients with DM, 29 and 73 were treated with and without CD26/DPP-4 inhibitors, respectively. Based on propensity score adjustment using standardized mortality ratio weighting, the 5-year OS rates were 77.0% and 44.3%, and the 5-year CLAD-free survival rates 77.8% and 49.1%, in patients treated with and without CD26/DPP-4 inhibitors, respectively. The hazard ratio for CD26/DPP-4 inhibitor use was 0.34 (95% confidence interval (CI) 0.14-0.82, p = 0.017) for OS and 0.47 (95% CI 0.22-1.01, p = 0.054) for CLAD-free survival. We detected CD26/DPP-4 expression in the CLAD grafts of patients without CD26/DPP-4 inhibitors. CONCLUSIONS: Analysis using propensity score weighting showed that CD26/DPP-4 inhibitors positively affected the postoperative prognosis of LTx patients with DM.

CXCR2 inhibition overcomes ponatinib intolerance by eradicating chronic myeloid leukemic stem cells through PI3K/Akt/mTOR and dipeptidylpeptidase â £ (CD26).

This study explores the therapeutic potential of targeting CXCR2 in patients afflicted with ponatinib-resistant chronic myeloid leukemia (CML). Ponatinib, a third-generation tyrosine kinase inhibitor (TKI), was initially designed for treating patients with CML harboring the T315I mutation. However, resistance or intolerance issues may lead to treatment discontinuation. Additionally, TKIs have exhibited limitations in eradicating quiescent CML stem cells. Our investigation reveals the activation of CXC chemokine receptor 2 (CXCR2) signaling in response to chemotherapeutic stress. Treatment with the CXCR2 antagonist, SB225002, effectively curtails cell proliferation and triggers apoptosis in ponatinib-resistant CML cells. SB225002 intervention also results in the accumulation of reactive oxygen species and disruption of mitochondrial function, phenomena associated with TKI chemoresistance and apoptosis. Furthermore, we demonstrate that activated CXCR2 expression induces the activity of dipeptidylpeptidase Ⅳ (DPP4/CD26), a CML leukemic stem cell marker, and concomitantly inhibits the PI3K/Akt/mTOR pathway cascades. These findings underscore the novel role of CXCR2 in the regulation of not only ponatinib-resistant CML cells, but also CML leukemic stem cells. Consequently, our study proposes that targeting CXCR2 holds promise as a viable therapeutic strategy for addressing patients with CML grappling with ponatinib resistance.

Sitagliptin Induces Tolerogenic Human Dendritic Cells.

Sitagliptin, an anti-diabetic drug, is a dipeptidyl peptidase (DPP)-4/CD26 inhibitor with additional anti-inflammatory and immunomodulatory properties. In this study, we investigated for the first time the effect of sitagliptin on the differentiation and functions of human dendritic cells generated from monocytes (MoDCs) for 4 days using the standard GM-CSF/IL-4 procedure. LPS/IFN-γ treatment for an additional 24 h was used for maturation induction of MoDCs. Sitagliptin was added at the highest non-cytotoxic concentration (500 µg/mL) either at the beginning (sita 0d protocol) or after MoDC differentiation (sita 4d protocol). Sitagliptin impaired differentiation and maturation of MoDCs as judged with the lower expression of CD40, CD83, CD86, NLRP3, and HLA-DR, retention of CD14 expression, and inhibited production of IL-ß, IL-12p70, IL-23, and IL-27. In contrast, the expression of CD26, tolerogenic DC markers (ILT4 and IDO1), and production of immunoregulatory cytokines (IL-10 and TGF-ß) were increased. Generally, the sita 0d protocol was more efficient. Sitagliptin-treated MoDCs were poorer allostimulators of T-cells in MoDC/T-cell co-culture and inhibited Th1 and Th17 but augmented Th2 and Treg responses. Tolerogenic properties of sitagliptin-treated MoDCs were additionally confirmed by an increased frequency of CD4+CD25+CD127- FoxP3+ Tregs and Tr1 cells (CD4+IL-10+FoxP3-) in MoDC/T-cell co-culture. The differentiation of IL-10+ and TGF-ß+ Tregs depended on the sitagliptin protocol used. A Western blot analysis showed that sitagliptin inhibited p65 expression of NF-kB and p38MAPK during the maturation of MoDCs. In conclusion, sitagliptin induces differentiation of tolerogenic DCs, and the effect is important when considering sitagliptin for treating autoimmune diseases and allotransplant rejection.

Immunomodulatory activity of dipeptidyl peptidase-4 inhibitors in immune-related diseases.

Dipeptidyl peptidase-4 (DPP-4), also known as CD26, is a 110-kDa cell surface glycoprotein with enzymatic and signal transducing activity. DPP-4/CD26 is expressed by various cells, including CD4+ and CD8+ T cells, B cells, dendritic cells, macrophages, and NK cells. DPP-4 inhibitors (DPP-4i) were introduced to clinics in 2006 as new oral antihyperglycemic drugs approved for type 2 diabetes mellitus treatment. In addition to glucose-lowering effects, emerging data, from clinical studies and their animal models, suggest that DPP-4i could display anti-inflammatory and immunomodulatory effects as well, but the molecular and immunological mechanisms of these actions are insufficiently investigated. This review focuses on the modulatory activity of DPP-4i in the immune system and the possible application of DPP-4i in other immune-related diseases in patients with or without diabetes.

Development of a Novel CD26-Targeted Chimeric Antigen Receptor T-Cell Therapy for CD26-Expressing T-Cell Malignancies.

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.

Minimal Residual Disease Detection at RNA and Leukemic Stem Cell (LSC) Levels: Comparison of RT-qPCR, d-PCR and CD26+ Stem Cell Measurements in Chronic Myeloid Leukemia (CML) Patients in Deep Molecular Response (DMR).

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.