H3K27me3 and VEGF is associated with poor prognosis in patients with synovial sarcoma

Purpose

Previous studies have shown a correlation between the expression of H3K27me3 and pathological characteristics of malignant tumors. This study aimed to investigate the association of H3K27me3 and VEGF expression with clinical outcomes of synovial sarcoma patients.

RBL cells as models for in vitro studies of mast cells and basophils

Since their establishment in 1981, RBL-2H3 cells have been widely used as a mast cell (MC) model. Their ability to be easily grown in culture in large amounts, their responsiveness to FcεRI-mediated triggers and the fact that they can be genetically manipulated, have provided advantages over primary MCs, in particular for molecular studies relying on genetic screening. Furthermore, the ability to generate clones that stably express proteins of interest, for example, a human receptor, have marked the RBL cells as an attractive MC model for drug screening. Indeed, 3 RBL reporter cell lines (RS-ATL8, NFAT-DsRed, and NPY-mRFP) have been generated providing useful models for drug and allergen screening. Similarly, RBL cells stably expressing the human MrgprX2 receptor provide a unique paradigm for analyzing ligand interactions and signaling pathways of the unique human receptor. Finally, transient co-transfections of RBL cells allow functional genomic analyses of MC secretion by combining library screening with simultaneous expression of a reporter for exocytosis. RBL cells thus comprise powerful tools for the study of intracellular membrane trafficking and exocytosis and the detection of allergens, vaccine safety studies and diagnosis of allergic sensitization. Their recent uses as an investigative tool are reviewed here.     

From the Cover: Proton transfers are key elementary steps in ethylene polymerization on isolated chromium(III) silicates

Mononuclear Cr(III) surface sites were synthesized from grafting [Cr(OSi(O^tBu)₃)₃(tetrahydrofurano)₂] on silica partially dehydroxylated at 700 °C, followed by a thermal treatment under vacuum, and characterized by infrared, ultraviolet-visible, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy (XAS). These sites are highly active in ethylene polymerization to yield polyethylene with a broad molecular weight distribution, similar to that typically obtained from the Phillips catalyst. CO binding, EPR spectroscopy, and poisoning studies indicate that two different types of Cr(III) sites are present on the surface, one of which is active in polymerization. Density functional theory (DFT) calculations using cluster models show that active sites are tricoordinated Cr(III) centers and that the presence of an additional siloxane bridge coordinated to Cr leads to inactive species. From IR spectroscopy and DFT calculations, these tricoordinated Cr(III) sites initiate and regulate the polymer chain length via unique proton transfer steps in polymerization catalysis.Almost half of the world’s high-density polyethylene is produced by the Phillips catalyst, a silica-supported chromium oxide (CrO_x/SiO₂) (1). This catalyst is prepared by incipient wetness impregnation of a chromium salt on silica, followed by high temperature calcination. Contacting this material with ethylene forms the active reduced species in situ that polymerizes ethylene. The Phillips catalyst is active in the absence of activators that are typically required for polymerization catalysts (2). Despite 50 y of research, the catalytically active site and the initiation mechanism, particularly the formation of the first Cr–C bond, remain controversial. Numerous spectroscopic techniques [infrared (IR), ultraviolet-visible (UV-Vis), electron paramagnetic resonance (EPR), X-ray absorption spectroscopy (XAS), etc.] established that the Phillips catalyst contains a complex mixture of surface Cr species, of which only ∼10% are active in polymerization (3, 4). The low number of active sites is one of the main limiting factors in using spectroscopic methods to study this material because the spectroscopic signature mainly belongs to inactive species.Previous molecular approaches to determine the Phillips catalyst ethylene polymerization mechanism focused on systems containing preformed Cr–C bonds (5–7). We recently reported the preparation of well-defined silica-supported Cr(II) and Cr(III) dinuclear sites (8), where Cr(III) species are active polymerization sites, in contrast to Cr(II), which is consistent with extensive research on homogeneous chromium complexes (9–11). We proposed that these well-defined Cr(III) silicates initiate polymerization by the heterolytic cleavage of a C–H bond of ethylene on a Cr–O bond to form a Cr–vinyl species that is capable of inserting ethylene by a Cossee–Arlman mechanism (8). However, extensive studies on Phillips catalyst invoke mononuclear polymerization sites (12–18). Furthermore, direct evidence of the active site structure and the polymerization mechanism is critically needed. Here we investigate the preparation and the detailed characterization of isolated Cr(III) sites supported on silica, prepared by grafting [Cr^III(OSi(O^tBu)₃)₃(tetrahydrofurano; THF)₂] (19) on dehydroxylated silica and a subsequent thermal treatment under vacuum. These isolated Cr(III) sites are highly active in ethylene polymerization in the absence of coactivator. Computational investigations in combination with IR spectroscopy indicate that polymerization occurs on tricoordinate Cr(III) sites and involves two key proton transfer steps: (i) formation of the first Cr–C bond through the C–H activation of ethylene across a Cr–O bond and (ii) termination by the microreverse of the initiation step while chain growth occurs by classical Cossee–Arlman insertion polymerization (20, 21).