200 research outputs found
Management of chronic immune thrombocytopenic purpura: targeting insufficient megakaryopoiesis as a novel therapeutic principle
No full textAndreas Rank, Oliver Weigert, Helmut OstermannMedizinische Klinik III – Grosshadern, Klinikum der Ludwig Maximilians-Universitaet Munich, Munich, GermanyAbstract: Traditionally, anti-platelet autoantibodies accelerating platelet clearance from the peripheral circulation have been recognized as the primary pathopysiological mechanism in chronic immune thrombocytopenia (ITP). Recently, increasing evidence supports the co-existence of insufficient megakaryopoiesis. Inadequate low thrombopoietin (TPO) levels are associated with insufficient proliferation and differentiation of megakaryocytes, decreased proplatelet formation, and subsequent platelet release. Recently two novel activators of TPO receptors have been made available: romiplostim and eltrombopag. In several phase III studies, both agents demonstrated increase of platelet counts in about 80% of chronic ITP patients within 2 to 3 weeks. These agents substantially broaden the therapeutic options for patients with chronic ITP although long-term results are still pending. This review will provide an update on the current conception of underlying mechanisms in ITP and novel, pathophysiologically based treatment options.Keywords: immune thrombocytopenia, romiplostim, eltrombopag, megakaryopoiesi
Educational and Wage Risk: Social Insurance vs. Quality of Education
No full textIn this model of education, where individuals are exposed both to educational risk and to wage risk within the skilled sector, successful graduation depends both on individual effort to study and on public resources. We show that insuring the present risks is a dichotomic task: Wage risk is diversified ex post among the skilled by graduate taxation and skill-specific tuition fees. Educational risk of failure and inequality between skilled and unskilled workers are mitigated ex ante by enhancing the quality of education. The necessary expenditures are optimally financed by regressive tuition fees and the net revenue from the graduate tax.human capital investment, educational risk, wage risk, learning effort, graduate taxation, regressive tuition fees
Lysosomal Membrane Permeabilization Sensitizes Ctss-Hyperactive Tumors to BCL2-Targeting Therapies
No full textHyperactivity of the cysteine protease cathepsin S (CTSS) -either through Y132 mutations or amplification/overexpression- is a recurrent alteration in follicular lymphoma (FL) and promotes tumor growth by inducing a supportive immune microenvironment (Bararia et al, 2020). Of note, patients with CTSS-hyperactive FL had better outcomes with standard therapies, suggesting that CTSS-hyperactivity can sensitize tumors to treatment. CTSS hyperactivity has also been reported in other B cell lymphomas (BCLs) (Dheilly et al, 2020) and solid cancers (Olson & Joyce, 2015).
CTSS is mainly localized intralysosomally but can be released into the cytosol by lysosomal membrane permeabilization (LMP). Low level LMP can occur spontaneously (e.g., during cell division) and can be enhanced by treatment. Unlike other cathepsins, cytosolically released CTSS maintains its enzymatic activity at non-acidic pH. Thus, we aimed to (i) identify the determinants of the cytosolic CTSS activity, (ii) determine its impact on the regulation of apoptosis, and (iii) study LMP as a therapeutic approach for CTSS-hyperactive tumors.
First, we accrued biochemical, functional, and clinical data supporting the role of cystatin B (CSTB) as a clinically relevant endogenous CTSS inhibitor in BCLs. Through unbiased and complementary proteomics (BioID2 labelling and co-IP followed by LC-MS/MS) we identified CSTB as a direct CTSS-interacting protein (8-fold enriched in the BCL cell line Karpas422 engineered to express CTSS wild type (WT) or Y132D vs CTSS knock-out (KO), P=0.0002). Single-cell RNA-Seq of primary FL (N=10) showed significantly higher CSTB expression in FL cells compared to normal B cells ( P=0.004). Moreover, shRNA mediated knock-down (k/d) of CSTB increased the overall cathepsin activity in BCL cell lines (N=8) by 1.5 to 5.5-fold, most notably in CTSS-hyperactive cells ( Fig A, top). We next employed LMP-inducing tool compounds (LLOMe) and clinically used drugs or analogs (desipramine, hexamethylene amiloride) to release cathepsins into the cytosol. CTSS-hyperactive Karpas422 were significantly more sensitive to LMP-inducing treatments compared to native cells (1.5 to 10-fold reduction of IC50). Importantly, CTSS hyperactivity and CSTB k/d increased LMP-mediated cell killing ( Fig A, bottom). Thus, the cytosolic CTSS/CSTB interaction determines the net cytosolic cathepsin activity and sensitivity of cells to undergo LMP-induced cell death.
Next, we hypothesized that LMP-induced cytosolic CTSS hyperactivity could prime BCLs towards apoptosis. We used BH3 profiling to functionally quantify the dependencies and interactions of BCL2 family members in BCLs with and without CTSS hyperactivity. In Karpas422 cells expressing CTSS Y132D, LMP increased overall apoptotic priming and dependencies on the anti-apoptotic proteins MCL-1 (delta priming >30 % at 10 µM, P=0.04), BCL-xL (>45 % at 10 µM, P=0.0006) and BCL2 (> 45 % at 0.5 and 1 µM, P=0.0001). We hypothesized that BCL2 family members are proteolytically cleaved by cytosolic CTSS. Indeed, e.g., BCL2 protein levels were 2.5 to 3.5-fold lower in LLOMe-treated Karpas422 cells with CTSS-hyperactivity compared to CTSS KO, and CSTB k/d further decreased BCL2 levels. To validate CTSS-mediated cleavage of BCL2, we purified FLAG-tagged BCL2 and CTSS WT and Y132D. CTSS WT efficiently cleaved BCL2 in vitro <1 hour at the top ranked predicted cleavage site and the reaction rate increased 1.3-fold for CTSS Y132D.
Finally, we hypothesized that LMP sensitizes cells to BCL2-targeting therapies ( Fig B). The combination of LLOMe-induced LMP and the BCL2 inhibitor venetoclax (VEN) showed increased cytotoxicity in CTSS-hyperactive Karpas422 cells compared to monotherapy and CSTB k/d enhanced this phenotype ( Fig A, bottom). We assessed cathepsin activities and generated dose-response curves for VEN with and without LLOMe-induced LMP in 15 primary CLL samples. Thereof, 12 samples had intermediate or high cathepsin activities and LLOMe-induced LMP increased their sensitivity to VEN, including a VEN-resistant sample in which the IC50 decreased to <3 nM.
In summary, we show that CSTB is a functionally relevant inhibitor that determines the net activity of LMP-released cytosolic CTSS. Furthermore, LMP-inducing therapies may be a promising approach to sensitize CTSS-hyperactive tumors towards apoptosis by proteolytic cleavage of BCL2 family members
Influence of Heparins on Pancreatic Cancer Cell Adhesion to Endothelial Cells in-vitro
No full textBegleitende Heparinmedikation führte in klinischen Studien zu einer Prognoseverbesserung bei onkologischen Patienten. Dieser Überlebensvorteil beruht nicht ausschließlich auf Prävention und Therapie thromboembolischer Komplikationen, sondern repräsentiert einen zusätzlichen, spezifischen Effekt auf maligne Prozesse. Die zugrundeliegenden Vorgänge und die Beobachtung, dass fraktionierte Heparine (LMWH) den unfraktionierten Heparinen diesbezüglich überlegen erscheinen, sind bislang ungeklärt. Am Beispiel des Pankreaskarzinoms wurde die Interaktion von Endothel- und Tumorzellen in-vitro untersucht. Präinkubation von Endothelzellen mit LMWH vor proinflammatorischer Zytokinstimulation (IL-1β, TNFα) führte zu einer verminderten Tumorzelladhäsion. Assoziiert war eine verminderte zytokinstimulierte Expression des Adhäsionsmoleküls E-Selektin auf Endothelzellen und eine reduzierte E-Selektin mRNS Synthese. Möglicherweise interferieren internalisierte Heparinderivate mit der NF-kB Signalkaskade.Concomitant heparin medication has been shown to improve prognosis of cancer patients in clinical trials. This survival advantage can not be fully attributed to prevention and treatment of thromboembolic events, but represents an additional and specific effect on the malignant process. The underlying mechanisms and the superiority of low molecular weight heparins (LMWH) remain incompletely understood. The interaction of endothelial and pancreatic cancer cells were investigated in-vitro. Preincubation of endothelial cells with LMWH prior to stimulation with proinflammatory cytokines (IL-1β, TNFα) resulted in decreased tumor cell adhesion. This was accompanied by decreased expression of the endothelial adhesion molecule E-selectin and reduced E-selectin mRNA synthesis. Internalized heparin fragments may interfere with cytosolic molecules of the NF-κB signaling pathway
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