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The inhibitory receptor TIGIT, as well as theectonucleotidases CD39 and CD73 constitute potential exhaustion markers for T cells. Detailed analysis of these markers can shed light into dysregulation of the T-cell response in acute myeloid leukemia (AML) and will help to identify potential therapeutic targets. The phenotype and expression of transcription factors was assessed on different T-cell populations derived from peripheral blood (PB, n = 38) and bone marrow (BM, n = 43). PB and BM from patients with AML diagnosis, in remission and at relapse were compared with PB from healthy volunteers (HD) (n = 12) using multiparameter flow cytometry. An increased frequency of terminally differentiated (CD45R-CCR7-)CD8+ T cells was detected in PB and BM regardless of the disease state. Moreover, we detected an increased frequency of two distinct T-cell populations characterized by the co-expression of PD-1 or CD39 on TIGIT+CD73-CD8- T cells in newly diagnosed and relapsed AML in comparison to HDs. In contrast to the PD-1+TIGIT+CD73-CD8+ T-cell population, the frequency of CD39+TIGIT+CD73-CD8+ T cells was normalized in remission. PD-1+- and CD39+TIGIT+CD73-CD8+ T cells exhibited additional features of exhaustion by decreased expression of CD127 and TCF-1 and increased intracellular expression of the transcription factor TOX. CD8+ T cells in AML exhibit a key signature of two subpopulations, PD-1+TOX+TIGIT+CD73-CD8+- and CD39+TOX+TIGIT+CD73-CD8+ T cells that were increased at different stages of the disease. These results provide a rationale to analyze TIGIT blockade in combination with inhibition of the purinergic signaling and depletion of TOX to improve T-cell mediated cytotoxicity in AML. [ABSTRACT FROM AUTHOR]

Comprehensive characterization of AML-associated T cells during disease progression is essential to identify relevant immune escape mechanisms and new immunotherapeutic approaches. Investigating the processes that lead to an immunosuppressive environment under progression of AML is difficult in humans, because by the time of diagnosis the disease is often progressed far beyond the initial stages. Therefore, to investigate T-cell phenotypes during progression a C57BL/6 mouse model was used. The CD3 + T cells were characterized by performing multiparametric flow analyses at different time points (day 0 = healthy mice, day 7, day 14, and day 21). The study revealed that the spleen is highly infiltrated by reg CD4 + T cells at day 21 of AML progression. These spleen-infiltrating reg CD4 + T cells mainly showed an effector memory differentiation with high expression and co-expression of the checkpoint molecules TIGIT, PD-1, OX40, and the two ectoenzymes CD39 and CD73. Substantial expression of the checkpoint molecules was restricted to the central memory and effector memory compartments. Furthermore, functional evaluation of TIGIT was performed. Blocking TIGIT resulted in a significantly increased lysis of C1498 AML cells in cocultures with AML-primed CD3 + T cells. Together these data confirm that the expression of the checkpoint receptor TIGIT is relevant for dysfunction of AML-associated T cells and, thus, represents a suitable target for future immunotherapeutic approaches.

Immune exhaustion is a hallmark of ovarian cancer. Using multiparametric flow cytometry, the study aimed to analyze protein expression of novel immunological targets on CD3 + T cells isolated from the peripheral blood ( n  = 20), malignant ascites ( n  = 16), and tumor tissue ( n  = 6) of patients with ovarian cancer (OVCA). The study revealed an increased proportion of effector memory CD8 + T cells in OVCA tissue and malignant ascites. An OVCA-characteristic PD-1 high CD8 + T cell population was detected, which differed from PD-1 low CD8 + T cells by increased co-expression of TIGIT, CD39, and HLA-DR. In addition, these OVCA-characteristic CD8 + T cells showed reduced expression of the transcription factor TCF-1, which may also indicate reduced effector function and memory formation. On the contrary, the transcription factor TOX, which significantly regulates terminal T cell-exhaustion, was found more frequently in these cells. Further protein and gene analysis showed that CD39 and CD73 were also expressed on OVCA tumor cells isolated from solid tumors ( n  = 14) and malignant ascites ( n  = 9). In the latter compartment, CD39 and CD73 were also associated with the expression of the "don't eat me" molecule CD24 on tumor cells. Additionally, ascites-derived CD24 + EpCAM + tumor cells showed a higher frequency of CD39 + or CD73 + cells. Furthermore, CD39 expression was associated with unfavorable clinical parameters. Expression of CD39 on T cells was upregulated through CD3/CD28 stimulation and its blockade by a newly developed nanobody construct resulted in increased proliferation (eFluor), activation (CD25 and CD134), and production of cytotoxic cytokines (IFN-γ, TNF-α, and granzyme-B) of CD8 + T cells., Competing Interests: The authors have no conflicts of interest to disclose., (© 2024 The Author(s). Published with license by Taylor & Francis Group, LLC.)

Introduction: Tumor-associated macrophages (TAMs) represent an important cell population within the tumor microenvironment, but little is known about the phenotype and function of these cells. The present study aims to characterize macrophages in high-grade serous ovarian cancer (HGSOC)., Methods: Phenotype and expression of co-regulatory markers were assessed on TAMs derived from malignant ascites (MA) or peripheral blood (PB) by multiparametric flow cytometry. Samples were obtained from HGSOC patients (n=29) and healthy donors (HDs, n=16). Additional expression analysis was performed by RNAseq (n=192). Correlation with clinically relevant parameters was conducted and validated by a second patient cohort (n=517). Finally, the role of TIGIT in repolarization and phagocytosis was investigated in vitro ., Results: Expression of the M2-associated receptors CD163, CD204, and CD206, as well as of the co-regulatory receptors TIGIT, CD226, TIM-3, and LAG-3 was significantly more frequent on macrophages in HGSOC than in HDs. CD39 and CD73 were broadly expressed on (mainly M2) macrophages, but without a clear clustering in HGSOC. CD163 mRNA levels were higher in TAMs from patients with residual tumor mass after surgery and associated with a shorter overall survival. In addition, TIGIT expression was associated with a higher tumor grading, indicating a prognostic relevance of M2 infiltration in HGSOC. TIGIT blockade significantly reduced the frequency of M2 macrophages. Moreover, combined blockade of TIGIT and CD47 significantly increased phagocytosis of ovarian cancer cells by TAMs in comparison to a single blockade of CD47., Conclusion: Combined blockade of TIGIT and CD47 represents a promising approach to enhance anti-CD47-facilitated phagocytosis., Competing Interests: Author TS was employed by the company 2cureX GmbH. CB: Personal fees from AOK Germany, med update, Roche Pharma, Astra Zeneca, Bayer Healthcare, BioNTech, Bristol Myers Squipp, Jansen Cilag, Merck Serono, Oncology Drug Consult CRO, Sanofi Aventis; Invited speaker by AOK Germany, med update, Roche Pharma; Advisory board by Astra Zeneca, Bayer Healthcare, BioNTech, Bristol Myers Squipp, Jansen Cilag, Merck Serono, Oncology Drug Consult CRO, Sanofi Aventis. FB: Travel grants Daiichi Sankyo, Servier, Novartis; advisory board by Jazz. GmbH, Daiichi Sankyo. WF: personal fees and non-financial support from AbbVie; grants, personal fees, and non-financial support from Amgen and Pfizer; and personal fees from Jazz Pharmaceuticals, Celgene, Morphosys, Ariad/Incyte, stem line therapeutics Daiichi Sankyo, and Servier outside the submitted work; in addition, WF has a patent for Amgen issued; and support for medical writing: Amgen, Pfizer, AbbVie. BS: Consulting and advisory board for Astra Zeneca, Roche, MSD, EISAI, GSK, Olympus; honoraria for presentations from Astra Zeneca, Roche, GSK, MSD, Clovis; travel grants Astra Zeneca, Roche, GSK; support for research from Roche, MSD, GSK, Astra Zeneca. JW: patent for Amgen issued. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Brauneck, Oliveira-Ferrer, Muschhammer, Sturmheit, Ackermann, Haag, Schulze zur Wiesch, Ding, Qi, Hell, Schmalfeldt, Bokemeyer, Fiedler and Wellbrock.)

The search for new and effective treatment targets for cancer immunotherapy is an ongoing challenge. Alongside the more established inhibitory immune checkpoints, a novel potential target is CD73. As one of the key enzymes in the purinergic signalling pathway CD73 is responsible for the generation of immune suppressive adenosine. The expression of CD73 is higher in tumours than in the corresponding healthy tissues and associated with a poor prognosis. CD73, mainly by the production of adenosine, is critical in the suppression of an adequate anti-tumour immune response, but also in promoting cancer cell proliferation, tumour growth, angiogenesis, and metastasis. The upregulation of CD73 and generation of adenosine by tumour or tumour-associated immune cells is a common resistance mechanism to many cancer treatments such as chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Therefore, the inhibition of CD73 represents a new and promising approach to increase therapy efficacy. Several CD73 inhibitors have already been developed and successfully demonstrated anti-cancer activity in preclinical studies. Currently, clinical studies evaluate CD73 inhibitors in different therapy combinations and tumour entities. The initial results suggest that inhibiting CD73 could be an effective option to augment anti-cancer immunotherapeutic strategies. This review provides an overview of the rationale behind the CD73 inhibition in different treatment combinations and the role of CD73 as a prognostic marker.

Background: Leukemia-associated macrophages (LAMs) represent an important cell population within the tumor microenvironment, but little is known about the phenotype, function, and plasticity of these cells. The present study provides an extensive characterization of macrophages in patients with acute myeloid leukemia (AML)., Methods: The phenotype and expression of coregulatory markers were assessed on bone marrow (BM)-derived LAM populations, using multiparametric flow cytometry. BM and blood aspirates were obtained from patients with newly diagnosed acute myeloid leukemia (pAML, n=59), patients in long-term remission (lrAML, n=8), patients with relapsed acute myeloid leukemia (rAML, n=7) and monocyte-derived macrophages of the blood from healthy donors (HD, n=17). LAM subpopulations were correlated with clinical parameters. Using a blocking anti-T-cell immunoreceptor with Ig and ITIM domains (TIGIT) antibody or mouse IgG2α isotype control, we investigated polarization, secretion of cytokines, and phagocytosis on LAMs and healthy monocyte-derived macrophages in vitro., Results: In pAML and rAML, M1 LAMs were reduced and the predominant macrophage population consisted of immunosuppressive M2 LAMs defined by expression of CD163, CD204, CD206, and CD86. M2 LAMs in active AML highly expressed inhibitory receptors such as TIGIT, T-cell immunoglobulin and mucin-domain containing-3 protein (TIM-3), and lymphocyte-activation gene 3 (LAG-3). High expression of CD163 was associated with a poor overall survival (OS). In addition, increased frequencies of TIGIT + M2 LAMs were associated with an intermediate or adverse risk according to the European Leukemia Network criteria and the FLT3 ITD mutation. In vitro blockade of TIGIT shifted the polarization of primary LAMs or peripheral blood-derived M2 macrophages toward the M1 phenotype and increased secretion of M1-associated cytokines and chemokines. Moreover, the blockade of TIGIT augmented the anti-CD47-mediated phagocytosis of AML cell lines and primary AML cells., Conclusion: Our findings suggest that immunosuppressive TIGIT + M2 LAMs can be redirected into an efficient effector population that may be of direct clinical relevance in the near future., Competing Interests: Competing interests: FB: travel grant from Daiichi Sankyo, Servier, and Novartis; advisory board by Jazz, GmbH, Daiichi Sankyo. WF: personal fees and non-financial support from AbbVie; grants, personal fees, and non-financial support from Amgen and Pfizer; and personal fees from Jazz Pharmaceuticals, Celgene, Morphosys, Ariad/Incyte, Stemline Therapeutics, Daiichi Sankyo, and Servier outside the submitted work; in addition, WF has a patent for Amgen issued; and support for medical writing: Amgen, Pfizer, and AbbVie. The remaining authors declare that they have no conflict of interest., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Recently new treatments for acute myeloid leukemia (AML) emerged, including regimens like CPX-351 and cladribine with cytarabine and daunorubicin (DA + C), demonstrating improved survival in patient subsets. This retrospective analysis is comparing the outcome of 124 patients treated with cytarabine and daunorubicin (DA; n  = 54), CPX-351 ( n  = 26) and DA + C ( n  = 44). Complete response rate following one cycle of therapy was increased in DA + C (62%) compared to CPX-351 (42%) and DA (50%). CPX-351 demonstrated a significant increased survival post allogenic stem cell transplantation against DA (hazard ratio (HR): 4.9; 95% confidence interval (95%CI): 1.1-21, p  = 0.03). Median survival was reached for DA (5.6 years) but not for DA + C or CPX-351. Subgroup analysis showed that AML with myelodysplasia-related changes and therapy-related AML treated with CPX-351 had increased survival compared to DA (HR: 5.2; 95%CI: 1.2-22; p  = 0.03). Our findings point twoards a CPX-351 superiority. However, the use of DA + C should be further evaluated in comparative studies.

Thymocyte selection-associated high mobility group box (TOX) has been described to be a key regulator in the formation of CD8+ T cell exhaustion. Hepatitis C virus (HCV) infection with different lengths of antigen exposure in acute, chronic, and after resolution of HCV infection is the ideal immunological model to study the expression of TOX in HCV-specific CD8+ T cells with different exposure to antigen. HCV-specific CD8+ T cells from 35 HLA-A*01:01, HLA-A*02:01, and HLA-A*24:02 positive patients were analyzed with a 16-color FACS-panel evaluating the surface expression of lineage markers (CD3, CD8), ectoenzymes (CD39, CD73), markers of differentiation (CD45RO, CCR7, CD127), and markers of exhaustion and activation (TIGIT, PD-1, KLRG1, CD226) and transcription factors (TOX, Eomesodermin, T-bet). Here, we defined on-target T cells as T cells against epitopes without escape mutations and off-target T cells as those against a "historical" antigen mutated in the autologous sequence. TOX+HCV-specific CD8+ T cells from patients with chronic HCV and on-target T cells displayed co-expression of Eomesodermin and were associated with the formation of terminally exhausted CD127 - PD1 hi , CD39 hi , CD73 low CD8+ T cells. In contrast, TOX+HCV-specific CD8+ T cells in patients with off-target T cells represented a progenitor memory Tex phenotype characterized by CD127 hi expression and a CD39 low and CD73 hi phenotype. TOX+HCV-specified CD8+ T cells in patients with a sustained virologic response were characterized by a memory phenotype (CD127+, CD73 hi ) and co-expression of immune checkpoints and Eomesodermin, indicating a key structure in priming of HCV-specific CD8+ T cells in the chronic stage, which persisted as a residual after therapy. Overall, the occurrence of TOX+HCV-specific CD8+ T cells was revealed at each disease stage, which impacted the development of progenitor Tex, intermediate Tex, and terminally exhausted T cell through an individual molecular footprint. In sum, TOX is induced early during acute infection but is modulated by changes in viral sequence and antigen recognition. In the case of antigen persistence, the interaction with Eomesodermin leads to the formation of terminally exhausted virus-specific CD8+ T cells, and there was a direct correlation of the co-expression of TOX and Eomes and terminally exhausted phenotype of virus-specific CD8+ T cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wildner, Walker, Brauneck, Ditt, Peine, Huber, Haag, Beisel, Timm and Schulze zur Wiesch.)

Phenotypic characterization of γδ T cells in the MALs (malignant ascites lymphocytes), TILs (tumor infiltrating lymphocytes), and PBLs (peripheral blood lymphocytes) of ovarian cancer (OvCA) patients is lacking. Therefore, we quantified γδ T cell prevalence in MAL, TIL, and PBL specimens from n = 18 OvCA patients and PBL from age-matched healthy donors (HD, n = 14). Multicolor flow cytometry was performed to evaluate the expression of inhibitory receptors (TIGIT, PD-1 and TIM-3), stimulatory receptors (Ox40), and purinergic ectoenzymes (CD39 and CD73) on γδ T cell subsets. We identified an abundant infiltration of Vδ1 T cells in the MALs and TILs. These cells varied in their differentiation: The majority of Vδ1 TILs displayed an effector memory (EM) phenotype, whereas Vδ1 MALs had a more mature phenotype of terminally differentiated effector memory cells (TEMRA) with high CD45RA expression. TIGIT and TIM-3 were abundantly expressed in both MALs and PBLs, whereas Vδ1 TILs exhibited the highest levels of PD-1, CD39, and Ox40. We also observed specific clusters on mature differentiation stages for the analyzed molecules. Regarding co-expression, Vδ1 TILs showed the highest levels of cells co-expressing TIGIT with PD-1 or CD39 compared to MALs and PBLs. In conclusion, the Vδ1 T cell population showed a high prevalence in the MALs and primary tumors of OvCA patients. Due to their (co-)expression of targetable immune receptors, in particular TIGIT with PD-1 and CD39 in TILs, Vδ1 T cell-based approaches combined with the inhibition of these targets might represent a promising strategy for OvCA.

Modern cancer therapies increased the survival rates of acute myeloid leukemia (AML) patients tremendously. However, the complexity of the disease and the identification of new targets require the adaptation of treatment protocols to reduce side effects and increase benefit for the patients. One key regulator of leukemogenesis and chemotherapy resistance in AML is the Hedgehog (HH) signaling pathway. It is deregulated in numerous cancer entities and inhibition of its downstream transcription factors GLI translates into anti-leukemic effects. One major regulator of GLI is BRD4, a BET family member with epigenetic functions. We investigated the effect of ZEN-3365, a novel BRD4 inhibitor, on AML cells in regard to the HH pathway. We show that ZEN-3365 alone or in combination with GANT-61 reduced GLI promoter activity, cell proliferation and colony formation in AML cell lines and primary cells. Our findings strongly support the evaluation of the BRD4 inhibitor ZEN-3365 as a new therapeutic option in AML., (© 2021. The Author(s).)

This study aimed to characterize different natural killer (NK) cell phenotypes on bone marrow and peripheral blood cells from acute myeloid leukemia (AML) patients and healthy donors (HDs). Our data show that CD56 dim CD16 - and CD56 bright CD16 - NK cells represent the predominant NK cell subpopulations in AML, while the CD56 dim CD16 + NK cells are significantly reduced compared to HDs. Moreover, TIGIT + and PVRIG + cells cluster on the CD56 dim CD16 + subset whereas CD39 + and CD38 + cells do so on CD56 bright CD16 - NK cells in AML. Furthermore, functional effects of (co-)blockade of TIGIT and CD39 or A2AR on NK cell functionality were analyzed. These experiments revealed that the single blockade of the TIGIT receptor results in an increased NK-92 cell-mediated killing of AML cells in vitro. Combined targeting of CD39 or A2AR significantly augments the anti-TIGIT-mediated lysis of AML cells. Our data indicate that distinct NK cell subsets in AML exhibit different immunosuppressive patterns (via the TIGIT/PVRIG receptors and the purinergic pathway). In summary, we conclude that TIGIT, CD39, and A2AR constitute relevant inhibitory checkpoints of NK cells in AML patients. A combinatorial blockade synergistically strengthens NK-92 cell-mediated cytotoxicity. As inhibitors of TIGIT, CD39, and A2AR are clinically available, studies on their combined use could be conducted in the near future.

Background: γδ T cells represent a unique T cell subpopulation due to their ability to recognize cancer cells in a T cell receptor- (TCR) dependent manner, but also in a non-major histocompatibility complex- (MHC) restricted way via natural killer receptors (NKRs). Endowed with these features, they represent attractive effectors for immuno-therapeutic strategies with a better safety profile and a more favorable anti-tumor efficacy in comparison to conventional αβ T cells. Also, remarkable progress has been achieved re-activating exhausted T lymphocytes with inhibitors of co-regulatory receptors e.g., programmed cell death protein 1 (PD-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT) and of the adenosine pathway (CD39, CD73). Regarding γδ T cells, little evidence is available. This study aimed to immunophenotypically characterize γδ T cells from patients with diagnosed acute myeloid leukemia (AML) in comparison to patients with multiple myeloma (MM) and healthy donors (HD). Methods: The frequency, differentiation, activation, and exhaustion status of bone marrow- (BM) derived γδ T cells from patients with AML ( n = 10) and MM ( n = 11) were assessed in comparison to corresponding CD4 + and CD8 + T cells and peripheral blood- (PB) derived γδ T cells from HDs ( n = 16) using multiparameter flow cytometry. Results: BM-infiltrating Vδ1 T cells showed an increased terminally differentiated cell population (TEMRAs) in AML and MM in comparison to HDs with an aberrant subpopulation of CD27 - CD45RA ++ cells. TIGIT, PD-1, TIM-3, and CD39 were more frequently expressed by γδ T cells in comparison to the corresponding CD4 + T cell population, with expression levels that were similar to that on CD8 + effector cells in both hematologic malignancies. In comparison to Vδ2 T cells, the increased frequency of PD-1 + -, TIGIT + -, TIM-3 + , and CD39 + cells was specifically observed on Vδ1 T cells and related to the TEMRA Vδ1 population with a significant co-expression of PD-1 and TIM-3 together with TIGIT. Conclusion: Our results revealed that BM-resident γδ T cells in AML and MM express TIGIT, PD-1, TIM-3 and CD39. As effector population for autologous and allogeneic strategies, inhibition of co-inhibitory receptors on especially Vδ1 γδ T cells may lead to re-invigoration that could further increase their cytotoxic potential., Competing Interests: FB: Travel grant Daiichi Sankyo, Servier, Novartis; advisory board by Jazz. GmbH, Daiichi Sankyo. WF: Membership on an entity's board of directors or advisory Amgen, ARIAD/Incucyte, Pfizer, Novartis, Jazz Pharmaceuticals, Morphosys, Abbvie, Celgene; patents and royalities: Amgen; other support for meeting attendance Amgen, Gilead, Jazz Pharmaceuticals, Servier, Daiichi Sankyo; research funding Amgen, Pfizer. Travel grant, advisory board and research funding by Amgen Inc., travel grant and advisory board by TEVA GmbH, the advisory board: Ariad/Incucyte Inc., travel grant by Gilead Inc and Jazz. GmbH, research funding by Pfizer Inc. KW: Honoraria: AbbVie, Amgen, Adaptive Biotech, Celgene/BMS, GSK, Janssen, Karyopharm, Novartis, Roche, Takeda, Sanofi; Research funding: Amgen, Celgene, Janssen, Sanofi. LL: Non-financial support from GSK and from Abbvie. CB: Travel grant: Astra Zeneca, Bayer Healthcare, Berlin Chemie, Bristol Myers Squipp, Jansen Cilag, Merck Serono, Merck Sharp Dohme, Novartis, Roche Pharma, Sanofi Aventis; Advisory board: Astra Zeneca, Bayer Healthcare, Berlin Chemie, Bristol Myers Squipp, Jansen Cilag, Merck Serono, Merck Sharp Dohme, Novartis, Roche Pharma, Sanofi Aventis; Invited speaker: AOK Germany, med update, Merck Serono; Honoraria: AOK Germany, Astra Zeneca, Bayer Healthcare, Berlin Chemie, GSO Research Organisation, Jansen Cilag, med update, Merck Serono, Merck Sharp Dohme, Novartis, Roche Pharma, Sanofi Aventis. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor declared a past co-authorship with the authors JW and WF., (Copyright © 2021 Brauneck, Weimer, Schulze zur Wiesch, Weisel, Leypoldt, Vohwinkel, Fritzsche, Bokemeyer, Wellbrock and Fiedler.)

The prognosis of elderly AML patients is still poor due to chemotherapy resistance. The Hedgehog (HH) pathway is important for leukemic transformation because of aberrant activation of GLI transcription factors. MBZ is a well-tolerated anthelmintic that exhibits strong antitumor effects. Herein, we show that MBZ induced strong, dose-dependent anti-leukemic effects on AML cells, including the sensitization of AML cells to chemotherapy with cytarabine. MBZ strongly reduced intracellular protein levels of GLI1/GLI2 transcription factors. Consequently, MBZ reduced the GLI promoter activity as observed in luciferase-based reporter assays in AML cell lines. Further analysis revealed that MBZ mediates its anti-leukemic effects by promoting the proteasomal degradation of GLI transcription factors via inhibition of HSP70/90 chaperone activity. Extensive molecular dynamics simulations were performed on the MBZ-HSP90 complex, showing a stable binding interaction at the ATP binding site. Importantly, two patients with refractory AML were treated with MBZ in an off-label setting and MBZ effectively reduced the GLI signaling activity in a modified plasma inhibitory assay, resulting in a decrease in peripheral blood blast counts in one patient. Our data prove that MBZ is an effective GLI inhibitor that should be evaluated in combination to conventional chemotherapy in the clinical setting.

The inhibitory receptor TIGIT, as well as theectonucleotidases CD39 and CD73 constitute potential exhaustion markers for T cells. Detailed analysis of these markers can shed light into dysregulation of the T-cell response in acute myeloid leukemia (AML) and will help to identify potential therapeutic targets.  The phenotype and expression of transcription factors was assessed on different T-cell populations derived from peripheral blood (PB, n = 38) and bone marrow (BM, n = 43). PB and BM from patients with AML diagnosis, in remission and at relapse were compared with PB from healthy volunteers (HD) ( n = 12) using multiparameter flow cytometry. An increased frequency of terminally differentiated (CD45R - CCR7 - )CD8 + T cells was detected in PB and BM regardless of the disease state. Moreover, we detected an increased frequency of two distinct T-cell populations characterized by the co-expression of PD-1 or CD39 on TIGIT + CD73 - CD8 + T cells in newly diagnosed and relapsed AML in comparison to HDs. In contrast to the PD-1 + TIGIT + CD73 - CD8 + T-cell population, the frequency of CD39 + TIGIT + CD73 - CD8 + T cells was normalized in remission. PD-1 + - and CD39 + TIGIT + CD73 - CD8 + T cells exhibited additional features of exhaustion by decreased expression of CD127 and TCF-1 and increased intracellular expression of the transcription factor TOX. CD8 + T cells in AML exhibit a key signature of two subpopulations, PD-1 + TOX + TIGIT + CD73 - CD8 + - and CD39 + TOX + TIGIT + CD73 - CD8 + T cells that were increased at different stages of the disease. These results provide a rationale to analyze TIGIT blockade in combination with inhibition of the purinergic signaling and depletion of TOX to improve T-cell mediated cytotoxicity in AML. Abbreviations : AML: Acute myeloid leukemia; pAML: newly diagnosed AML; rAML: relapse AML; lrAML: AML in remission; HD: healthy donor; PB: peripheral blood; BM: bone marrow; TIGIT: T-cell immunoreceptor with Ig and ITIM domains; PD-1: Programmed cell death protein 1; CD73: ecto-5'-nucleotidase; CD39: ectonucleoside triphosphate diphosphohydrolase 1; ATP: adenosine triphosphate; ADO: adenosine; CD127: interleukin-7 receptor; CAR-T cell: chimeric antigen receptor T cell; TCF-1: transcription factor T-cell factor 1; TOX: Thymocyte selection-associated high mobility group box protein; NFAT: nuclear factor of activated T cells; NA: Naïve; CM: Central Memory; EM Effector Memory; EMRA: Terminal Effector Memory cells; FMO: Fluorescence minus one; PVR: poliovirus receptor; PVRL2: poliovirus receptor-related 2; IFN-γ: Interferon-γ; IL-2: interleukin-2; MCF: multiparametric flow cytometry; TNFα: Tumornekrosefaktor α; RT: room temperature., (© 2021 The Author(s). Published with license by Taylor & Francis Group, LLC.)

B cells play a central role in antiviral and antiparasitic immunity, not only as producers of antibodies, but also as APCs and mediators of inflammation. In this study, we used 16-color flow cytometry analysis to investigate the frequency, differentiation, and activation status of peripheral B cells of patients with SARS-CoV-2 infection or acute Plasmodium falciparum malaria compared with the healthy individuals. As a main result, we observed an increase of the frequency of (CD27 - , CD21 - ) atypical memory B cells and (CD19 + , CD27 + , CD38 + ) plasmablasts in malaria and COVID-19 patients. Additionally, CD86, PD-1, CXCR3, and CD39 expression was up-regulated, whereas CD73 was down-regulated on plasmablasts of COVID-19 and malaria patients compared with the bulk B cell population. In particular, there was a more pronounced loss of CD73 + B cells in malaria. The frequency of plasmablasts positively correlated with serum levels of CRP, IL-6, and LDH of COVID-19 patients. In the longitudinal course of COVID-19, a rapid normalization of the frequency of atypical memory B cells was observed. The role and function of plasmablasts and atypical memory B cells in COVID-19 and other acute infections remain to be further investigated. The role of B cells as either "driver or passenger" of hyperinflammation during COVID-19 needs to be clarified., (© 2020 The Authors. Journal of Leukocyte Biology published by Wiley Periodicals LLC on behalf of Society for Leukocyte Biology.)

Immune checkpoints are intensively investigated as targets in cancer therapy. T-cell immunoreceptor with immunoglobulin (Ig) and ITIM domains (TIGIT) and its ligand poliovirus receptor (PVR) are recently emerging as novel promising targets in immunotherapy. Here, we show that high expression of PVR represents an independent prognostic marker being associated with poor outcome for breast cancer patients. Furthermore, PVR mRNA, as well as protein expression, is associated with more aggressive breast cancer subtypes such as HER2 positive and triple-negative breast cancer. In vitro , blocking TIGIT or PVR resulted in enhanced immune cell-mediated lysis of breast cancer cell lines SKBR-3, MDA-MB-231, MDA-MB-468, and BT549 and additionally increased the cytotoxic effects of a bispecific T cell engager BiTE® antibody construct targeting EGFR. Taken together, our data identify the immune checkpoint factor PVR as a novel prognostic marker in breast cancer and indicate that blocking the TIGIT-PVR axis might represent a novel therapeutic option for the treatment of breast cancer patients., (© 2019 Taylor & Francis Group, LLC.)