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We have previously developed an antibody fusion protein composed of a mouse/human chimeric IgG3 specific for the human transferrin receptor genetically fused to avidin (anti-hTfR IgG3-Av) as a universal delivery system for cancer therapy. This fusion protein efficiently delivers biotinylated FITC into cancer cells via TfR-mediated endocytosis. In addition, anti-hTfR IgG3-Av alone exhibits intrinsic cytotoxic activity and interferes with hTfR recycling, leading to the rapid degradation of the TfR and lethal iron deprivation in certain malignant B-cell lines. We now report on the cytotoxic effects of a conjugate composed of anti-hTfR IgG3-Av and biotinylated saporin 6 (b-SO6), a toxin derived from the plant Saponaria officinalis that inhibits protein synthesis. Conjugation of anti-hTfR IgG3-Av with b-SO6 enhances the cytotoxic effect of the fusion protein in sensitive cells and also overcomes the resistance of malignant cells that show low sensitivity to the fusion protein alone. Our results show for the first time that loading anti-hTfR IgG3-Av with a biotinylated toxin enhances the cytotoxicity of the fusion protein alone. These results suggest that anti-hTfR IgG3-Av has great potential as a therapeutic agent for a wide range of applications due to its intrinsic cytotoxic activity plus its ability to deliver biotinylated molecules into cancer cells.

BAFF plays a central role in B-lineage cell biology; however, the regulation of BAFF-binding receptor (BBR) expression during B cell activation and differentiation is not completely understood. In this study, we provide a comprehensive ex vivo analysis of BBRs in human B-lineage cells at various stages of maturation, as well as describe the events that drive and regulate receptor expression. Our data reveal that B-lineage cells ranging from naive to plasma cells (PCs), excluding bone marrow PCs, express BAFF-R uniformly. In contrast, only tonsillar memory B cells (MB) and PCs, from both tonsil and bone marrow tissues, express BCMA. Furthermore, we show that TACI is expressed by MB cells and PCs, as well as a subpopulation of activated CD27(neg) B cells. In this regard, we demonstrate that TACI is inducible early upon B cell activation and this is independent of B cell turnover. In addition, we found that TACI expression requires activation of the ERK1/2 pathway, since its expression was blocked by ERK1/2-specific inhibitors. Expression of BAFF-R and B cell maturation Ag (BCMA) is also highly regulated and we demonstrate that BCMA expression is only acquired in MB cells and in a manner accompanied by loss of BAFF-R expression. This inverse expression coincides with MB cell differentiation into Ig-secreting cells (ISC), since blocking differentiation inhibited both induction of BCMA expression and loss of BAFF-R. Collectively, our data suggest that the BBR profile may serve as a footprint of the activation history and stage of differentiation of normal human B cells.

We have previously shown that coculture of human embryonic stem cells (hESCs) for 14 days with immortalized fetal hepatocytes yields CD34(+) cells that can be expanded in serum-free liquid culture into large numbers of megaloblastic nucleated erythroblasts resembling yolk sac-derived cells. We show here that these primitive erythroblasts undergo a switch in hemoglobin (Hb) composition during late terminal erythroid maturation with the basophilic erythroblasts expressing predominantly Hb Gower I (zeta(2)epsilon(2)) and the orthochromatic erythroblasts hemoglobin Gower II (alpha(2)epsilon(2)). This suggests that the switch from Hb Gower I to Hb Gower II, the first hemoglobin switch in humans is a maturation switch not a lineage switch. We also show that extending the coculture of the hESCs with immortalized fetal hepatocytes to 35 days yields CD34(+) cells that differentiate into more developmentally mature, fetal liver-like erythroblasts, that are smaller, express mostly fetal hemoglobin, and can enucleate. We conclude that hESC-derived erythropoiesis closely mimics early human development because the first 2 human hemoglobin switches are recapitulated, and because yolk sac-like and fetal liver-like cells are sequentially produced. Development of a method that yields erythroid cells with an adult phenotype remains necessary, because the most mature cells that can be produced with current systems express less than 2% adult beta-globin mRNA.

Human bone marrow multipotent mesenchymal stromal cells are progenitor cells that can be expanded in vitro and differentiate into various cells of mesodermal origin. They contribute to the bone marrow reticular niche, where mature B cells and long-lived plasma cells are maintained. Multipotent mesenchymal stromal cells were recently shown to modulate T- and B-cell proliferation and differentiation, dendritic cell maturation, and natural killer activity. These immunoregulatory properties encouraged a possible use of these cells to modulate autoimmune responses in humans. We studied the influence of bone marrow mesenchymal stem cells on highly purified B-cell subsets isolated from healthy donors and total B cells from pediatric systemic lupus erythematosus patients. Bone marrow mesenchymal stem cells promoted proliferation and differentiation into immunoglobulin-secreting cells of transitional and naive B cells stimulated with an agonist of Toll-like receptor 9, in the absence of B cell receptor triggering. They strongly enhanced proliferation and differentiation into plasma cells of memory B-cell populations. A similar effect was observed in response to polyclonal stimulation of B cells isolated from pediatric patients with systemic lupus erythematosus. This study casts important questions on bone marrow mesenchymal stem cells as a therapeutic tool in autoimmune diseases in which B-cell activation is crucially implicated in the pathogenesis of the disease.

The functional significance of the electrophysiological properties of neural precursor cells (NPCs) was investigated using dissociated neurosphere-derived NPCs from the forebrain subventricular zone (SVZ) of adult mice. NPCs exhibited hyperpolarized resting membrane potentials, which were depolarized by the K(+) channel inhibitor, Ba(2+). Pharmacological analysis revealed two distinct K(+) channel families: Ba(2+)-sensitive K(ir) channels and tetraethylammonium (TEA)-sensitive K(v) (primarily K(DR)) channels. Ba(2+) promoted mitogen-stimulated NPC proliferation, which was mimicked by high extracellular K(+), whereas TEA inhibited proliferation. Based on gene and protein levels in vitro, we identified K(ir)4.1, K(ir)5.1 and K(v)3.1 channels as the functional K(+) channel candidates. Expression of these K(+) channels was immunohistochemically found in NPCs of the adult mouse SVZ, but was negligible in neuroblasts. It therefore appears that expression of K(ir) and K(v) (K(DR)) channels in NPCs and related changes in the resting membrane potential could contribute to NPC proliferation and neuronal lineage commitment in the neurogenic microenvironment.

Implanted materials, such as medical devices, provoke the body to initiate an inflammatory reaction, known as the foreign body reaction (FBR), which causes several complications for example in hip prostheses, silicone implants, peritoneal dialysis catheters and left ventricular assist devices. FBR is initiated by macrophage adherence and results in granulation tissue formation. The early immunobiology and development of this tissue is not completely understood, but there are indications from related myofibroblast-forming diseases such as vascular repair and fibrosis that primitive stem cells also play a role in the formation of FBR-tissue. To investigate this, acellular photo-oxidized bovine pericardium patches were implanted intraperitoneally in rats and retrieved at time-points ranging from 6h to 7 days. A significant fraction of Sca-1(+) (6h-2 days), c-kit(+), CD34(+) and CD271(+) (2-3 days) stem/progenitor cells were detected. Colony-forming and differentiation capacity of the primitive stem cells into adipo-, osteo-, and myofibroblasts were shown. The presence of these primitive cells and their myofibroblastic differentiation potential were also confirmed at RNA level. The identification of specific primitive cells during FBR may have important implications for the inflammatory responses to inert materials and their use in tissue prostheses.

Human embryonic stem cells (hESC) can differentiate to cardiomyocytes in vitro but with generally poor efficiency. Here, we describe a novel method for the efficient generation of cardiomyocytes from hESC in a scalable suspension culture process. Differentiation in serum-free medium conditioned by the cell line END2 (END2-CM) readily resulted in differentiated cell populations with more than 10% cardiomyocytes without further enrichment. By screening candidate molecules, we have identified SB203580, a specific p38 MAP kinase inhibitor, as a potent promoter of hESC-cardiogenesis. SB203580 at concentrations textless10 microM, induced more than 20% of differentiated cells to become cardiomyocytes and increased total cell numbers, so that the overall cardiomyocyte yield was approximately 2.5-fold higher than controls. Gene expression indicated that early mesoderm formation was favored in the presence of SB203580. Accordingly, transient addition of the inhibitor at the onset of differentiation only was sufficient to determine the hESC fate. Patch clamp electrophysiology showed that the distribution of cardiomyocyte phenotypes in the population was unchanged by the compound. Interestingly, cardiomyogenesis was strongly inhibited at SB203580 concentrations textgreater or =15 microM. Thus, modulation of the p38MAP kinase pathway, in combination with factors released by END2 cells, plays an essential role in early lineage determination in hESC and the efficiency of cardiomyogenesis. Our findings contribute to transforming human cardiomyocyte generation from hESC into a robust and scalable process.

Over the past 5 years, the Raf kinase family has emerged as a promising target for protein-directed cancer therapy development. The goal of this review is to first provide a concise summary of the data validating Raf proteins as high-interest therapeutic targets. The authors then outline the mode of action of Raf kinases, emphasizing how Raf activities and protein interactions suggest specific approaches to inhibiting Raf. The authors then summarize the set of drugs, antisense reagents and antibodies available or in development for therapeutically targeting Raf or Raf-related proteins, as well as existing strategies combining these and other therapeutic agents. Finally, the authors discuss recent results from systems biology analyses that have the potential to increasingly guide the intelligent selection of combination therapies involving Raf-targeting agents and other therapeutics. View Publication

BACKGROUND: The enhancement of circulating endothelial progenitor cells (EPCs) obtained by exercise training can be beneficial to patients with cardiac disease. Changes in the levels and differentiation of CD34(pos)/KDR(pos) EPCs, as well as the plasma concentration of vascular endothelial growth factor (VEGF) and stromal cell-derived factor (SDF)-1 EPC-mobilizing cytokines, were evaluated in patients with chronic heart failure after 8 weeks of supervised aerobic training (SAT) and 8 weeks of subsequent discontinued SAT (DSAT). METHODS AND RESULTS: The levels of circulating EPC and EPC differentiation potential of 22 patients who underwent SAT were studied by fluorescence-activated cell sorter analysis and colony forming-unit assay, respectively. The plasma levels of VEGF and SDF-1 were measured by enzyme-linked immunosorbent assay. In response to SAT, the levels of both EPC and VEGF/SDF-1 markedly increased (P textless .001 vs baseline) but returned to the baseline levels after DSAT. A similar change was observed with the EPC clonogenic potential, but on DSAT the baseline level was incompletely attained. CONCLUSIONS: In response to SAT, patients with chronic heart failure show enhanced EPC levels and clonogenic potential that is mirrored by increased plasma VEGF and SDF-1 levels. DSAT can interfere with the maintenance of training-acquired VEGF/SDF-1-related EPC levels and clonogenic potential.

Thiazolidinediones (TZD) are widely prescribed for the treatment of Type 2 diabetes. Increased loss of bone mass and a higher incidence of fractures have been associated with the use of this class of drugs in post-menopausal women. In vitro studies performed in rodent cell models indicated that rosiglitazone (RGZ), one of the TZD, inhibited osteoblastogenesis and induced adipogenesis in bone marrow progenitor cells. The objective of the present study was to determine for the first time the RGZ-dependent shift from osteoblastogenesis toward adipogenesis using a human cell model. To this purpose, bone marrow-derived mesenchymal stem cells were characterized and induced to differentiate along osteogenic and adipogenic lineages. We found that the exposure to RGZ potentiated adipogenic differentiation and shifted the differentiation toward an osteogenic phenotype into an adipogenic phenotype, as assessed by the appearance of lipid droplets. Accordingly, RGZ markedly increased the expression of the typical marker of adipogenesis fatty-acid binding protein 4, whereas it reduced the expression of Runx2, a marker of osteoblastogenesis. This is the first demonstration that RGZ counteracts osteoblastogenesis and induces a preferential differentiation into adipocytes in human mesenchymal stem cells.

Glutathione (GSH) depletion is widely used to sensitize cells to anticancer treatment inducing the progression of programmed cell death and overcoming chemoresistance. It has been reported that neuroblastoma cells with MYCN amplification are unable to start TRAIL-dependent death and MYCN, in concert with cytotoxic drugs, efficiently induces the mitochondrial pathway of apoptosis through oxidative mechanisms. In this study, we show that GSH loss induced by L-buthionine-S,R-sulfoximine (BSO), an inhibitor of GSH biosynthesis, leads to overproduction of reactive oxygen species (ROS) and triggers apoptosis of MYCN-amplified neuroblastoma cells. BSO susceptibility of SK-N-BE-2C, a representative example of MYCN-amplified cells, has been attributed to stimulation of total SOD activity in the absence of changes in the level and the activity of catalase. Therefore, the unbalanced intracellular redox milieu has been demonstrated to be critical for the progression of neuroblastoma cell death that was efficiently prevented by antioxidants and rottlerin. These results describe a novel pathway of apoptosis dependent on ROS formation and PKC-delta activation and independent of p53, bcl-2, and bax levels; the selective redox modulation of PKC-delta might be suggested as a potential strategy for sensitizing MYCN-amplified cells to therapeutic approaches.

Aberrant expression of Jagged1 and Notch1 are associated with poor outcome in breast cancer. However, the reason that Jagged1 and/or Notch overexpression portends a poor prognosis is unknown. We identify Slug, a transcriptional repressor, as a novel Notch target and show that elevated levels of Slug correlate with increased expression of Jagged1 in various human cancers. Slug was essential for Notch-mediated repression of E-cadherin, which resulted in beta-catenin activation and resistance to anoikis. Inhibition of ligand-induced Notch signaling in xenografted Slug-positive/E-cadherin-negative breast tumors promoted apoptosis and inhibited tumor growth and metastasis. This response was associated with down-regulated Slug expression, reexpression of E-cadherin, and suppression of active beta-catenin. Our findings suggest that ligand-induced Notch activation, through the induction of Slug, promotes tumor growth and metastasis characterized by epithelial-to-mesenchymal transition and inhibition of anoikis.