904 Repurposing CD26 (DPP4) inhibitors to enhance immunotherapy response in pancreatic ductal adenocarcinoma

BackgroundPancreatic ductal adenocarcinoma (PDAC) is refractory to immunotherapy due in part to cellular cross-talk with cancer associated fibroblasts (CAFs). These interactions shape the microenvironment in a manner that is profoundly immunosuppressive. Our group is identifying novel targets in the PDAC stroma that can be manipulated to enhance immunotherapy efficacy. We hypothesize dysregulation of the serine protease, CD26/DPP4 in PDAC contributes to the limited efficacy of immunotherapy. Further, we posit targeting CD26 enzymatic activity using inhibitors that are FDA-approved for adult patients with Type 2 Diabetes Mellitus can enhance the efficacy of immunotherapy in PDAC.MethodsPrimary CAFs isolated from patient PDAC resection specimens under an IRB-approved protocol, were subject to NanoString analysis.1 CD26 protein expression was measured in primary and immortalized CAFs and PDAC cells by immunoblot, flow cytometry and immunofluorescence, while ELISA detected soluble CD26. For in vivo efficacy, luciferase-expressing KPC-tumor cells were implanted orthotopically in the pancreas of immune-competent C57BL/6 mice. Bioluminescence imaging (BLI) confirmed established tumors and mice were randomized to sitagliptin (75 mg/kg in drinking water, CD26/DPP4 inhibitor), anti-PD-L1 Ab (200 ug 2x/week), or both combined for 3 weeks. Controls received vehicle or isotype control Ab. BLI utilized to track tumor progression and tissues harvested for analysis at study endpoint (day 18 of treatment).ResultsNanoString analysis identified CD26/DPP4 as significantly upregulated in RNA transcripts from primary CAFs vs. fibroblasts from normal pancreas (figure 1). We confirmed abundant CD26 expression on patient-derived CAFs and immortalized CAF cell lines, however, lower CD26 expression was observed on human PDAC cell lines (HPAC, PANC-1) by immunoblot, flow cytometry and immunofluorescence (figure 5).Abstract 904 Figure 1(A) Schema for analysis of transcript from n=10 primary CAFs (PSC) from PDAC patients vs. normal human pancreatic fibroblasts (HPPFC) via NanoString nCounter PanCancer Immune Profiling Panel. (B) Heat map of gene expression with upregulate DPP4 or CD26 transcript detected. Adapted from Mace et al., 2016.Abstract 904 Figure 2Validation of CD26 protein expression in human PDAC-derived CAF and PDAC cell lines by immunoblot analysisAbstract 904 Figure 3Analysis of surface human CD26 expression in PBMCs, PDAC-derived CAFs (h-iPSC-PDAC-1), and PDAC cells (PANC-1) by flow cytometry. Histograms representing human surface CD26 expressionAbstract 904 Figure 4Immunofluorescence analysis of CD26/DPP4 cellular localization in a human PDAC-derived CAF cell lineAbstract 904 Figure 5Combined Sitagliptin and PD-L1 blockade in a murine orthotopic model of PDAC. Fold change in tumor volume, determined by BLI, comparing baseline (Day 0 of treatment) to Day 18 of treatment. Each bar represents fold change in BLI determined tumor volume for each animalConclusionsOur results are the first to describe CD26 expression on PDAC-derived CAFs and indicate that sitagliptin augments anti-tumor activity of anti-PD-L1 in PDAC tumor-bearing mice. Our ongoing work will provide insight into specific immune cell populations responsible for efficacy of immunotherapy in murine models of PDAC, and the role of CD26 in various cellular compartments within the PDAC microenvironment.ReferencesMace TA, Shakya R, Pitarresi JR, Swanson B, McQuinn CW, Loftus S, Nordquist E, Cruz-Monserrate Z, Yu L, Young G, Zhong X, Zimmers TA, Ostrowski MC, Ludwig T, Bloomston M, Bekaii-Saab T, Lesinski GB. IL-6 and PD-L1 antibody blockade combination therapy reduces tumour progression in murine models of pancreatic cancer. Gut 2018;67(2):320–32.

Distinctive CD26 Expression on CD4 T-Cell Subsets

Immune system CD4 T-cells with high cell-surface CD26 expression show anti-tumoral properties. When engineered with a chimeric antigen receptor (CAR), they incite strong responses against solid cancers. This subset was originally associated to human CD4 T helper cells bearing the CD45R0 effector/memory phenotype and later to Th17 cells. CD26 is also found in soluble form (sCD26) in several biological fluids, and its serum levels correlate with specific T cell subsets. However, the relationship between glycoprotein sCD26 and its dipeptidyl peptidase 4 (DPP4) enzymatic activity, and cell-surface CD26 expression is not well understood. We have studied ex vivo cell-surface CD26 and in vitro surface and intracellular CD26 expression and secretome’s sCD26 in cultured CD4 T cells under different polarization conditions. We show that most human CD26negative CD4 T cells in circulating lymphocytes are central memory (TCM) cells while CD26high expression is present in effector Th1, Th2, Th17, and TEM (effector memory) cells. However, there are significant percentages of Th1, Th2, Th17, and Th22 CD26 negative cells. This information may help to refine the research on CAR-Ts. The cell surface CD45R0 and CD26 levels in the different T helper subsets after in vitro polarization resemble those found ex vivo. In the secretomes of these cultures there was a significant amount of sCD26. However, in all polarizations, including Th1, the levels of sCD26 were lower (although not significantly) compared to the Th0 condition (activation without polarization). These differences could have an impact on the various physiological functions proposed for sCD26/DPP4.

CD26 expression on donor harvest as a risk predictive biomarker for developing Graft-versus-Host Disease post-Allogeneic Hematopoietic Stem Cell Transplantation: A tenyear followup study

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (ASCT) is the preferred treatment option for patients with several hematologic disorders and immunodeficiency syndromes. Graft versus host disease (GVHD) is an immune mediated post-transplant complication which has a major impact on long term transplant outcomes. OBJECTIVE: Current efforts are focused on identification of new markers that serve as potential predictors of GVHD and other post-transplant clinical outcomes. METHODS: This study includes donor harvests collected from twenty-three allogeneic donors during period 2008–2009 and respective transplant recipients followed for clinical outcomes till March 2019. Percent CD26+ and CD34+ cells in donor harvest were analyzed using flow cytometry. Percent expression and infused dose of CD26+ and CD34+ cells were evaluated for association with various clinical outcomes. RESULTS: Total 23 healthy donors 28 years (13 males), and transplant recipients with median age 24 years (17 males) formed the study cohort. The diagnosis included malignant (n= 13) and non-malignant (n= 10) disorders. Median CD34brCD45lo HSC expression was 057% (IQR 024–103) while median CD26 expression was 1964% (IQR 896–3356) of all nucleated cells. CD26 expression was associated with donor age (P= 0.37). CD26 percent expression correlated with WBC engraftment (P= 0.015) and with acute GVHD (P= 0.023) whereas infused CD26 cell dose correlated with WBC engraftment (P= 0.004) and risk of CMV reactivation (P= 0.020). There was no statistically significant correlation of either CD26 expression or cell dose with chronic GVHD, EFS or OS.

Involvement of CD26 in Differentiation and Functions of Th1 and Th17 Subpopulations of T Lymphocytes

CD26, acting as a costimulator of T cell activation, plays an important role in the immune system. However, the role of CD26 in the differentiation of T cell subsets, especially of new paradigms of T cells, such as Th17 and Tregs, is not fully clarified. In the present study, the role of CD26 in T cell differentiation was investigated in vitro. CD26 expression was analyzed in the different subsets of human peripheral blood T lymphocytes after solid-phase immobilized specific anti-CD3 mAb stimulation. Here, the percentage of CD4+ cells significantly increased and most of these cells were coexpressed with CD26, suggesting a close correlation of CD26 expression with the proliferation of CD4+ cells. Subsequently, after immobilized anti-CD3 mAb stimulation, CD26 high-expressing cells (CD26high) were separated from CD26 low-expressing cells (CD26low) by magnetic cell sorting. We found that the percentages of cells secreting Th1 typical cytokines (IL-2, IFN-γ) and Th17 typical cytokines (IL-6, IL-17, and IL-22) or expressing Th17 typical biomarkers (IL-23R, CD161, and CD196) in the CD26high group were markedly higher than in those in the CD26low group. In addition, a coexpression of CD26 with IL-2, IFN-γ, IL-17, IL-22, and IL-23R in lymphocytes was demonstrated by fluorescence microscopy. These results provide direct evidence that the high expression of CD26 is accompanied by the differentiation of T lymphocytes into Th1 and Th17, indicating that CD26 plays a crucial role in regulating the immune response.

Identification of human CD4+ T cell populations with distinct antitumor activity

How naturally arising human CD4+ T helper subsets affect cancer immunotherapy is unclear. We reported that human CD4+CD26high T cells elicit potent immunity against solid tumors. As CD26high T cells are often categorized as TH17 cells for their IL-17 production and high CD26 expression, we posited these populations would have similar molecular properties. Here, we reveal that CD26high T cells are epigenetically and transcriptionally distinct from TH17 cells. Of clinical importance, CD26high and TH17 cells engineered with a chimeric antigen receptor (CAR) regressed large human tumors to a greater extent than enriched TH1 or TH2 cells. Only human CD26high T cells mediated curative responses, even when redirected with a suboptimal CAR and without aid by CD8+ CAR T cells. CD26high T cells cosecreted effector cytokines, produced cytotoxic molecules, and persisted long term. Collectively, our work underscores the promise of CD4+ T cell populations to improve durability of solid tumor therapies.

Reduction of endoglin receptor impairs mononuclear cell-migration

Aim: To test if the impairment of mononuclear cell (MNC) migration in patients with hereditary hemorrhagic telangiectasia (HHT) is due to the reduction of the endoglin (ENG) receptor on the cell surface and oxidative stress. Method: MNCs of HHT patients and normal controls were subjected to migration assay. Fractions of MNCs were pre-incubated with antibodies specific to HHT causative genes ENG [hereditary hemorrhagic telangiectasia type 1 (HHT1)] or activin receptor-like kinase 1 [ALK1, hereditary hemorrhagic telangiectasia type 2 (HHT2)], AMD3100 or Diprotin-A to block ENG, ALK1 C-X-C chemokine receptor 4 (CXCR4) or CD26 (increased in HHT1 MNCs) before migration assay. The MNCs were allowed to migrate toward stromal cell-derived factor-1alpha (SDF-1alpha) for 18 h. The expression of CXCR4, CD26, superoxide dismutase 1 (SOD1) and glutathione peroxidase 1 (GPX1) in MNCs and nitric oxide levels in the plasma were analyzed. Results: Compared to the controls, fewer HHT1 MNCs and similar number of HHT2 MNCs migrated toward SDF-1. Diprotin-A pre-treatment improved HHT1 MNC-migration, but had no effect on normal and HHT2 MNCs. Pre-incubation with an anti-ENG antibody reduced the migration of normal MNCs. Diprotin-A did not improve the migration of ENG antibody pre-treated MNCs. Anti-ALK1 antibody had no effect on MNC-migration. AMD3100 treatment reduced normal and HHT MNC-migration. ENG mRNA level was reduced in HHT1 and HHT2 MNCs. ALK1 mRNA was reduced in HHT2 MNCs only. CD26 expression was higher in HHT1 MNCs. Pre-treatment of MNCs with anti-ENG or anti-ALK1 antibody had no effect on CD26 and CXCR4 expression. The expression of antioxidant enzymes, SOD1, was reduced in HHT1 MNCs, which was accompanied with an increase of ROS in HHT MNCs and nitric oxide in HHT1 plasma. Conclusions: Reduction of ENG receptor on MNC surface reduced monocyte migration toward SDF-1alpha independent of CD26 expression. Increased oxidative stress could alter HHT MNC migration behavior.

Single-Antibody Detection of T-Cell Receptor Beta Chain Monotypia Resolves Uncertainties in the Identification and Quantitation of Sézary Cells By Routine Flow Cytometry: Towards Accurate and Unequivocal Blood Staging of Cutaneous T-Cell Lymphomas

BACKGROUND: Sézary syndrome and mycosis fungoides are two clinically distinct neoplasias of CD4-positive skin-resident T-cells that share remarkable morphologic and immunophenotypic similarities, commonly referred together as cutaneous T-cell lymphoma (CTCL). Prognostic clinical staging in CTCL requires flow cytometric quantitation of peripheral blood tumor cells (Sézary cells), based on aberrant loss of CD7 and/or CD26 within the CD4-positive T-cell compartment. Unfortunately, similar T-cell populations are frequently encountered in reactive conditions, creating uncertainty in the diagnostic interpretation. We recently reported a flow cytometric strategy to assess T-cell clonality using a single antibody (JOVI-1) against one of 2 mutually exclusive T-cell receptor beta constant (TRBC) regions randomly selected during T-cell receptor gene rearrangement. We hereby applied this strategy to a diagnostic Sézary cell flow cytometry panel, resulting in rapid, accurate and unequivocal identification and quantitation of clonal CD4-positive T-cells. METHODS: We studied 33 peripheral blood specimens from 24 patients with CTCL, and 28 specimens from patients with no clinical or laboratory evidence of T-cell malignancy. A routine Sézary cell flow cytometry panel (CD2/CD3/CD4/CD5/CD7/CD8/CD26/CD45) was modified to include a fluorescent labeled antibody against TRBC1. Gated CD4 T-cells were studied to identify discrete subsets lacking CD7, CD26 or both, in addition to other immunophenotypic abnormalities. Within each subset, clonality was defined as a dominant TRBC1-positive or TRBC1-negative population greater than 85%, or a dominant abnormal TRBC1-dim population, as previously described. RESULTS: Peripheral blood specimens from patients with CTCL showed subsets of CD4-positive T-cells lacking CD7 (median=35%; range 1.6% to 96%) or CD26 expression (median=54%; range 6.6% to 98%). Fifteen (45%) of these specimens had other identifiable phenotypic abnormalities, including decreased CD2, CD3, CD4 or CD5. Patients without a T-cell malignancy also had CD4-positive T-cells lacking CD7 (median=13%; range 0.5% to 38%) or CD26 expression (median=9.4%; range 0.7% to 30%), albeit to a lesser extent compared to CTCL patients (p<0.01 and p<0.0001 for CD7 and CD26, respectively). One febrile infant showed loss of CD2 on a small T-cell subset. Discrete CD4-positive T-cell subsets with monotypic TRBC expression were identified in 24 specimens (73%) from patients with CTCL (Figure A), ranging from 30 to12,000 cells/µL (median=632). Importantly, no TRBC-restricted CD4-positive T-cells were detected in any of the 28 patients without a T-cell malignancy. Nine specimens from CTCL patients without a TRBC-restricted subset were reviewed based on morphologic, immunophenotypic and clinical features, yielding no definitive evidence of Sézary cells. Absolute numbers of TRBC-restricted T-cells correlated with numbers of Sézary cells estimated based on lack of CD7 or CD26 expression (R=0.99), or absence of both antigens (R=0.7) (Figure B). However, all cases with no detectable clonal TRBC-restricted T-cells showed significant absolute numbers of CD4-positive T-cells lacking CD7 or CD26 (mean=208 cells/µL, range=22 to 1,078 cells/µL), resulting in common diagnostic uncertainties based on quantitation of these subsets. A narrower gating strategy on these same patients based on the combined loss of CD7 and CD26 yielded lower numbers of abnormal cells (mean=51 cells/µL, range=2 to 556 cells/µL), but grossly underestimated the number of TRBC-restricted CD4-positive T-cells by more than 500 cells/µL in 6 patients with CTCL (Figure B). CONCLUSIONS: A single anti-TRBC1 antibody added to a routine Sézary cell flow cytometry assay provides a rapid, simple and low-cost approach to query for clonality within immunophenotypically distinct CD4 T-cell subsets, eliminating the need for a separate T-cell clonality assay. Diagnostic uncertainties and quantitative biases resulting from immunophenotypic overlaps between Sézary cells and reactive T-cells are virtually resolved. Direct quantitation of clonal CD4 T-cells based on TRBC1 restriction is a biologically sound strategy for blood staging in CTCL, effectively overcoming the limitations and uncertainties of staging by immunophenotypic analysis based on current guidelines. Figure Disclosures Horna: MorphoSys AG: Research Funding.