Stroma-derived connective tissue growth factor maintains cell cycle progression and repopulation activity of hematopoietic stem cells in vitro

Funding Information: This project was supported by Technische Universität München, Graduate School of Bioengineering (GSB; http://www.bioengineering.gs.tum.de ), the German José Leukemia Research Foundation (DJCLS R 11/12), and the German Research Council (DFG OO 8/5, OO 8/9, and FOR 2033/1). We gratefully acknowledge the support of Prof. Torsten Buch, of the Expression Core Facility of the Institute of Medical Microbiology, Hygiene, and Immunology of the Technische Universität München. Publisher Copyright: © 2015 The Authors. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.Hematopoietic stem cells (HSCs) are preserved in co-cultures with UG26-1B6 stromal cells or their conditioned medium. We performed a genome-wide study of gene expression changes of UG26-1B6 stromal cells in contact with Lineage- SCA-1+ KIT+ (LSK) cells. This analysis identified connective tissue growth factor (CTGF) to be upregulated in response to LSK cells. We found that co-culture of HSCs on CTGF knockdown stroma (shCtgf) shows impaired engraftment and long-term quality. Further experiments demonstrated that CD34- CD48- CD150+ LSK (CD34- SLAM) cell numbers from shCtgf co-cultures increase in G0 and senescence and show delayed time to first cell division. To understand this observation, a CTGF signaling network model was assembled, which was experimentally validated. In co-culture experiments of CD34- SLAM cells with shCtgf stromal cells, we found that SMAD2/3-dependent signaling was activated, with increasing p27Kip1 expression and downregulating cyclin D1. Our data support the view that LSK cells modulate gene expression in the niche to maintain repopulating HSC activity.publishersversionPeer reviewe

Targeted inhibition of protein synthesis renders cancer cells vulnerable to apoptosis by unfolded protein response

AbstractCellular stress responses including the unfolded protein response (UPR) decide over the fate of an individual cell to ensure survival of the entire organism. During physiologic UPR counter-regulation, protective proteins are upregulated to prevent cell death. A similar strategy induces resistance to UPR in cancer. Therefore, we hypothesized that blocking protein synthesis following induction of UPR substantially enhances drug-induced apoptosis of malignant cells. In line, upregulation of the chaperone BiP was prevented by simultaneous arrest of protein synthesis in B cell malignancies. Cytotoxicity by immunotoxins—approved inhibitors of protein synthesis—was synergistically enhanced in combination with UPR-inducers in seven distinct hematologic and three solid tumor entities in vitro. Synergistic cell death depended on mitochondrial outer membrane permeabilization via BAK/BAX, which correlated with synergistic, IRE1α-dependent reduction of BID, accompanied by an additive fall of MCL-1. The strong synergy was reproduced in vivo against xenograft mouse models of mantle cell lymphoma, Burkitt’s lymphoma, and patient-derived acute lymphoblastic leukemia. In contrast, synergy was absent in blood cells of healthy donors suggesting a tumor-specific vulnerability. Together, these data support clinical evaluation of blocking stress response counter-regulation using inhibitors of protein synthesis as a novel therapeutic strategy.</jats:p

Protein kinase c-β-dependent activation of NF-κB in stromal cells is indispensable for the survival of chronic lymphocytic leukemia B cells in vivo

Tumor cell survival critically depends on heterotypic communication with benign cells in the microenvironrnent. Here, we describe a survival signaling pathway activated in stromal cells by contact to B cells from patients with chronic lymphocytic leukemia (CLL). The expression of protein kinase C (PKC)-beta II and the subsequent activation of NF-kappa B in bone marrow stromal cells are prerequisites to support the survival of malignant B cells. PKC-beta knockout mice are insusceptible to CLL transplantations, underscoring the in vivo significance of the PKC-beta II-NF-kappa B signaling pathway in the tumor microenvironment. Upregulated stromal PKG-beta II in biopsies from patients with CLL, acute lymphoblastic leukemia, and mantle cell lymphoma suggests that this pathway may commonly be activated in a variety of hematological malignancies

Inhibition of cholesterol recycling impairs cellular PrPSc propagation

The infectious agent in prion diseases consists of an aberrantly folded isoform of the cellular prion protein (PrPc), termed PrPSc, which accumulates in brains of affected individuals. Studies on prion-infected cultured cells indicate that cellular cholesterol homeostasis influences PrPSc propagation. Here, we demonstrate that the cellular PrPSc content decreases upon accumulation of cholesterol in late endosomes, as induced by NPC-1 knock-down or treatment with U18666A. PrPc trafficking, lipid raft association, and membrane turnover are not significantly altered by such treatments. Cellular PrPSc formation is not impaired, suggesting that PrPSc degradation is increased by intracellular cholesterol accumulation. Interestingly, PrPSc propagation in U18666A-treated cells was partially restored by overexpression of rab 9, which causes redistribution of cholesterol and possibly of PrPSc to the trans-Golgi network. Surprisingly, rab 9 overexpression itself reduced cellular PrPSc content, indicating that PrPSc production is highly sensitive to alterations in dynamics of vesicle trafficking

Successful treatment of COVID-19 infection with convalescent plasma in B-cell-depleted patients may promote cellular immunity

Treatment with convalescent plasma has been shown to be safe in coronavirus disease in 2019 (COVID-19) infection, although efficacy reported in immunocompetent patients varies. Nevertheless, neutralizing antibodies are a key requisite in the fight against viral infections. Patients depleted of antibody-producing B cells, such as those treated with rituximab (anti-CD20) for hematological malignancies, lack a fundamental part of their adaptive immunity. Treatment with convalescent plasma appears to be of general benefit in this particularly vulnerable cohort. We analyzed clinical course and inflammation markers of three B-cell-depleted patients suffering from COVID-19 who were treated with convalescent plasma. In addition, we measured serum antibody levels as well as peripheral blood CD38/HLA-DR-positive T-cells ex vivo and CD137-positive T-cells after in vitro stimulation with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-derived peptides in these patients. We observed that therapy with convalescent plasma was effective in all three patients and analysis of CD137-positive T-cells after stimulation with SARS-CoV-2 peptides showed an increase in peptide-specific T-cells after application of convalescent plasma. In conclusion, we here demonstrate efficacy of convalescent plasma therapy in three B-cell-depleted patients and present data that suggest that while application of convalescent plasma elevates systemic antibody levels only transiently, it may also boost specific T-cell responses

The role of microenvironment and immunity in drug response in leukemia

Leukemia is a cancer of the white blood cells, with over 54,000 new cases per year diagnosed worldwide and a 5-year survival rate below 60%. This highlights a need for research into the mechanisms behind its etiology and causes of therapy failure. The bone marrow microenvironment, in which adult stem cells are maintained in healthy individuals, has been implicated as a source of chemoresistance and disease relapse. Here the various ways that the microenvironment can contribute to the resistance and persistence of leukemia are discussed. The targeting of the microenvironment by leukemia cells to create an environment more suitable for cancer progression is described. The role of soluble factors, drug transporters, microvesicles, as well as the importance of direct cell–cell contact, in addition to the effects of inflammation and immune surveillance in microenvironment-mediated drug resistance are discussed. An overview of the clinical potential of translating research findings to patients is also provided. Understanding of and further research into the role of the bone marrow microenvironment in leukemia progression and relapse are crucial towards developing more effective treatments and reduction in patient morbidity