Increased frequency of TIGIT+CD73-CD8+ T cells with a TOX+ TCF-1low profile in patients with newly diagnosed and relapsed AML.

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.

SHIP1, but not an AML-derived SHIP1 mutant, suppresses myeloid leukemia growth in a xenotransplantation mouse model.

Constitutive activation of the PI3K/AKT signaling pathway is found in ~50-70% of AML patients. The SH2-containing inositol 5-phosphatase 1 (SHIP1) is a negative regulator of PI3K/AKT signaling in hematopoietic cells. SHIP1 knockout mice develop a myeloproliferative syndrome and concomitant deletion of SHIP1 and the tumor suppressor PTEN leads to the development of lethal B-cell lymphomas. In the study presented here, we investigated the role of SHIP1 as a tumor suppressor in myeloid leukemia cells in an in vivo xenograft transplantation model. NSG Mice transplanted with UKE-1 cells derived from a secondary AML showed a significantly extended lifespan after lentiviral-mediated overexpression of SHIP1 in comparison to the vector control cohort. In contrast, the AML-derived SHIP1Y643H mutant, which has a strongly reduced enzymatic activity showed a significant reversion of the SHIP1-induced prolongation of the survival time. In addition, the analysis of 290 AML patients revealed a correlation between expression of SHIP1 and overall survival of the AML patients. These results indicate that SHIP1 can act as a tumor suppressor in acute myeloid leukemia cells and that higher SHIP1 expression is associated with prolonged overall survival in AML patients. SHIP1 may be an interesting candidate for gene therapy.

Clinical experience with antiangiogenic therapy in leukemia.

The pathological role of bone marrow angiogenesis in human leukemias has been clearly established. Bone marrow neoangiogenesis is mediated by several growth factors, such as VEGF-A, VEGF-C, angiopoietin-1 and -2, FGF, HGF, TGF-ß and others secreted by leukemic cells. The prognostic relevance of microvessel density, and expression of VEGF-A and -C has been demonstrated especially in acute myeloid leukemia. In the last years, several classes of angiogenesis inhibitors have been developed blocking several angiogenic pathways. These include drugs that inhibit the VEGF (with or without blockade of FLT3) and the mTor signalling cascade. Besides, thalidomide and lenalidomide although possessing a pleiotrophic mode of action including antiangiogenic properities have been evaluated in the treatment of human leukemias. In the current review we analyze the results of clinical trials employing these antiangiogenic drugs. Since the clinical efficacy of these compounds used as monotherapy is often limited, confined to certain subgroups of patients and frequently short lived, several trials combining standard chemotherapy with these agents have been initiated in order to demonstrate an additional benefit to standard therapy. Furthermore the introduction of new antiangiogenic drugs such as inhibitors of the angiopoietin and HGF/cMET pathway is on the horizon. Utilizing cocktails of inhibitors of several angiogenic pathways may represent a new possibility to augment the efficacy of antiangiogenic therapy in the future.