Targeting the splicing factor NONO inhibits GBM progression through GPX1 intron retention.

Background: Splicing factors are essential for nascent pre-mRNA processing and critical in cancer progression, suggesting that proteins with splicing functions represent potential molecular targets for cancer therapy. Here, we investigate the role of splicing factors in glioblastoma multiforme (GBM) progression and the possibility of targeting them for the treatment of the disease. Methods: The TCGA and CGGA public databases were used to screen for differentially expressed mRNA splicing factors. Immunohistochemistry and qRT-PCR were used to analyze the expression of non-POU domain-containing octamer-binding protein (NONO), a Drosophila behavior human splicing (DBHS) protein. Knockdown/overexpression of NONO with siRNA and lentiviral expression constructs was used to examine cell growth, apoptosis, and invasion in GBM cells. RNA sequencing was used to identify potential downstream molecular targets of NONO. RIP-PCR and RNA pulldown were used to determine the interaction between NONO and pre-mRNA. JC-1 staining and the seahorse assay were performed to assess redox homeostasis. Results: Expression of NONO was increased in GBM samples and associated with poor survival in patients (P = 0.04). Knockdown of NONO suppressed GBM growth, and overexpression of NONO promoted GBM tumorigenesis in vitro and in vivo. RNA sequencing-based transcriptomic profiling confirmed that knockdown of NONO in U251 and P3 cells resulted in global intron retention of pre-mRNA and led to abnormal splicing of specific pre-mRNAs for GPX1 and CCN1. NONO bound to a consensus motif in the intron of GPX1 pre-mRNA in association with another DBHS protein family member, PSPC1. Knockdown of NONO impaired tumor growth, invasion, and redox homeostasis through aberrant splicing of GPX1. Finally, Auranofin, a small molecule inhibitor of NONO, suppressed GBM tumor growth in an orthotopic xenograft model in mice. Conclusions: We demonstrated that intron retention was a critical alternative RNA splicing event to occur in GBM progression, and that NONO was a key regulator of mRNA splicing in GBM. Targeting NONO represents a novel, potential therapeutic strategy for GBM treatment.

A Novel One-Pot Synthesis of Poly(Propylene Carbonate) Containing Cross-Linked Networks by Copolymerization of Carbon Dioxide, Propylene Oxide, Maleic Anhydride, and Furfuryl Glycidyl Ether.

The thermoplastic poly(propylene carbonate) (PPC) containing cross-linked networks was one-pot synthesized by copolymerization of carbon dioxide, propylene oxide (PO), maleic anhydride (MA), and furfuryl glycidyl ether (FGE). The copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements. The thermal and dimensional stability of the copolymers were improved. When the MA and FGE load increased from 1 mol% to 4 mol% of PO, the copolymers contained the gel contents of 11.0%-26.1% and their yields were about double that of the PPC. The 5% weight-loss degradation temperatures (Td,-5%) and the maximum weight-loss degradation temperatures (Td,max) increased from 149.7-271.3 °C and from 282.6-288.6 °C, respectively, corresponding to 217.1 °C and 239.0 °C of PPC. Additionally, the hot-set elongation tests showed that the copolymers exhibited elasticity and dimensional stability with the minimum permanent deformation of 6.5% which was far less than that of PPC of 157.2%, while the tensile strengths were a little lower than that of PPC because of the following two conflicting factors, cross-links and flexibility of the units formed by the introduced third monomers, MA and FGE. In brief, we provide a novel method of one-pot synthesis of PPC containing cross-linked networks. According to this idea, the properties would be more extensively regulated by changing the cross-linkable monomers.

Enhanced Poly(Propylene Carbonate) with Thermoplastic Networks: A One-Pot Synthesis from Carbon Dioxide, Propylene Oxide, and a Carboxylic Dianhydride.

Thermally and mechanically enhanced poly(propylene carbonate) (PPC) with networks was prepared by adding a cyclic carboxylic dianhydride, bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTCDA), in the CO2/propylene oxide (PO) copolymerization. The obtained copolymers were characterized by FT-IR, ¹H NMR, DSC, and TGA. The gel, melt flow rate, hot-set elongation, and tensile properties were also measured. The formation of networks was confirmed by the presence of gel and the shape recovery after the hot-set elongation test. The minimum permanent deformation of the copolymer is 3.8% and that of PPC is 4539% higher than this value. The results show that BTCDA units are inserted into the backbone of PPC, and the PPC chains are connected successfully owing to cyclic multifunctional anhydride groups in BTCDA. With increasing feed molar ratio of BTCDA to PO from 1 to 4%, the yield strength of copolymers increases from 18.1 to 37.4 MPa compared to 12.9 MPa of PPC. The 5% weight-loss degradation temperatures and maximum weight-loss degradation temperatures greatly increase up to 276.4 and 294.7 °C, respectively, which are 58.6 °C and 55.1 °C higher than those of PPC. These enhanced properties originate from the formation of crosslinks by the rigid and bulky multifunctional dianhydride.