Mesenchymal stromal cells (MSCs) possess numerous regenerative and immune modulating functions. Transplantation across histocompatibility barriers is feasible due to their hypoimmunogenicity. MSCs have emerged as promising tools for treating graft-versus-host disease following allogeneic stem cell transplantation. It is well established that their clinical efficacy is substantially attributed to fine-tuning of T-cell responses. At the same time, increasing evidence suggests that metabolic processes control T-cell function and fate. Here, we investigated the MSCs' impact on the metabolic framework of activated T-cells. In fact, MSCs led to mitigated mTOR signaling. This phenomenon was accompanied by a weaker glycolytic response (including glucose uptake, glycolytic rate, and upregulation of glycolytic machinery) toward T-cell activating stimuli. Notably, MSCs express indoleamine-2,3-dioxygenase (IDO), which mediates T-cell suppressive tryptophan catabolism. Our observations suggest that IDO-induced tryptophan depletion interferes with a tryptophan-sufficiency signal that promotes cellular mTOR activation. Despite an immediate suppression of T-cell responses, MSCs foster a metabolically quiescent T-cell phenotype characterized by reduced mTOR signaling and glycolysis, increased autophagy, and lower oxidative stress levels. In fact, those features have previously been shown to promote generation of long-lived memory cells and it remains to be elucidated how MSC-induced metabolic effects shape in vivo T-cell immunity. STEM CELLS 2016;34:516-521 SIGNIFICANCE STATEMENTMesenchymal stromal cells (MSCs) have emerged as a promising therapeutic option for a number of entities including Graft-versus-Host disease (GvHD) following stem cell transplantation. In GvHD the MSCs' beneficial effects can be attributed to their fine-tuning of T-cell responses. At the same time increasing evidence highlights that metabolic signaling governs T-cell function and fate. Here, we show for the first time how MSCs suppress T-cell activation by modulating their metabolism. However, several of the observed MSC-mediated metabolic effects are linked to memory formation and longevity in T-cells. Our findings could therefore represent an explanation why MSC-transfer in GvHD patients does not lead to an increased risk for disease relapse or infectious complications.

Sorafenib is a multi-kinase inhibitor with activity against several intracellular kinases which may play a role in the pathogenesis of acute myeloid leukemia (AML). In vitro data and results from early clinical trials suggest that sorafenib might be an effective drug for the treatment of AML. However, clinical data are still sparse, and there are only a few reported cases of monotherapy. The aim of the present research was to collect clinical data on efficacy and safety in a systematic way by conducting a survey on clinical experience with sorafenib. Thirty institutions were asked to document all patients treated with sorafenib diagnosed with AML. Of all 29 evaluable patients, six (21%) responded to sorafenib containing treatment by achieving a complete remission (CR, n = 2) or complete remission with incomplete platelet recovery (CRi, n = 4). In 23 patients receiving sorafenib as monotherapy, the CRi rate amounted to 13% and no CRs were documented. Of the 18 FLT-ITD positive patients with sorafenib monotherapy, two patients achieved a CRi (11%). In five FLT3-ITD negative cases, one CRi was documented (20%). Our results suggest the potential ability of the drug to induce remissions in refractory or relapsed AML even when given as monotherapy.

ZusammenfassungDas erhöhte Thrombose- und Blutungsrisiko bei aktiver Tumorerkrankung wird als sog. „thrombo-hämorrhagisches Syndrom“ bezeichnet, welches hohe Anforderungen an die Antikoagulation stellt. Aktuell liegen 4 randomisierte, prospektive Studien zum Einsatz von neuen, nicht Vitamin K-abhängigen oralen Antikoagulantien (NOAK) zur Behandlung von in der Onkologie aufgetretenen venösen Thromboembolien (VTE) vor. Dabei wurden die FXa-Inhibitoren Rivaroxaban, Edoxaban und zweimal Apixaban jeweils in einzelnen Studien gegenüber dem Standardtherapeutikum Dalteparin eingesetzt. Da es keinen direkten Head-to-Head-Vergleich der genannten FXa-Inhibitoren innerhalb einer Studie gibt, wurde zu jedem NOAK die jeweils größte Studie – stets verglichen gegenüber Dalteparin – ausgewertet. Die Studien wurden bzgl. ihrer Wirksamkeit, Sicherheit, fataler Blutungsraten, dem Risiko für gastrointestinale Blutungen (GIB) und sonstiger Unterschiede anhand deskriptiver Statistik analysiert. Unter Dalteparin ergab sich eine mittlere VTE-Rezidivrate von ca. 9% bei einem 6-monatigen Behandlungszeitraum. Alle 3 FXa-Inhibitoren waren gegenüber Dalteparin bezüglich der Wirksamkeit nicht unterlegen. Die VTE-Rezidivrate war bei mit Edoxaban und Apixaban behandelten Patienten um – 2,3% und bei Rivaroxaban um – 5,0% niedriger.Bei der Sicherheit fanden sich – jeweils gegenüber Dalteparin – für Rivaroxaban und Edoxaban eine erhöhte Rate an schweren Blutungen (jeweils +2,4%); insbesondere war hierbei die Zahl GIB deutlich erhöht. Dagegen war für Apixaban die Zahl schwerer Blutungen, wie auch für verschiedene Blutungstypen inkl. GIB, nicht erhöht. In der Apixabanstudie war insgesamt die Rate von schweren GIB, die ca. 50% aller schweren Blutungen ausmachten, und die der klinisch-relevanten nicht schweren Blutungen, am niedrigsten. Die FXa-Inhibitoren sind der Standardtherapie mit Dalteparin in der VTE-Rezidivrate bei onkologischen Patienten nicht unterlegen. Die GIB-Rate scheint ein wichtiger prädiktiver Faktor für die Sicherheit dieser Substanzgruppe zu sein, sodass Tumorlokalisation, gastrointestinale Risikofaktoren und andere individuelle Kriterien in Zukunft stärker bei der Therapieentscheidung für oder gegen einen FXa-Inhibitor berücksichtigt werden sollten.

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