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Articles by G Xu
Total Records ( 6 ) for G Xu
  Z Han , Z Hong , C Chen , Q Gao , D Luo , Y Fang , Y Cao , T Zhu , X Jiang , Q Ma , W Li , L Han , D Wang , G Xu , S Wang , L Meng , J Zhou and D. Ma

Tumor cells acquire the ability to proliferate uncontrollably, resist apoptosis, sustain angiogenesis and evade immune surveillance. Signal transducer and activator of transcription (STAT) 3 regulates all of these processes in a surprisingly large number of human cancers. Consequently, the STAT3 protein is emerging as an ideal target for cancer therapy. This paper reports the generation of an oncolytic adenovirus (M4), which selectively blocks STAT3 signaling in tumor cells as a novel therapeutic strategy. M4 selectively replicated in tumor cells and expressed high levels of antisense STAT3 complementary DNA during the late phase of the viral infection in a replication-dependent manner. The viral progeny yield of M4 in tumor cells was much higher than that of the parent adenoviral mutants, Ad5/dE1A. M4 effectively silenced STAT3 and its target genes in tumor cells while sparing normal cells and exhibited potent antitumoral efficacy in vitro and in vivo. Systemic administration of M4 significantly inhibited tumor growth in an orthotopic gastric carcinoma mouse model, eliminated abdominal cavity metastases and prolonged survival time. In summary, M4 has low toxicity and great potential as a therapeutic agent for different types of cancers.

  G Xu , T Watanabe , Y Iso , S Koba , T Sakai , M Nagashima , S Arita , S Hongo , H Ota , Y Kobayashi , A Miyazaki and T. Hirano

Rationale: Human heregulins, neuregulin-1 type I polypeptides that activate proliferation, differentiation, and survival of glial cells, neurons, and myocytes, are expressed in macrophage foam cells within human coronary atherosclerotic lesions. Macrophage foam cell formation, characterized by cholesterol ester accumulation, is modulated by scavenger receptor class A (SR-A), acyl-coenzyme A:cholesterol acyltransferase (ACAT)1, and ATP-binding cassette transporter (ABC)A1.

Objective: The present study clarified the roles of heregulins in macrophage foam cell formation and atherosclerosis.

Methods and Results: Plasma heregulin-β1 levels were significantly decreased in 31 patients with acute coronary syndrome and 33 patients with effort angina pectoris compared with 34 patients with mild hypertension and 40 healthy volunteers (1.3±0.3, 2.0±0.4 versus 7.6±1.4, 8.2±1.2 ng/mL; P<0.01). Among all patients with acute coronary syndrome and effort angina pectoris, plasma heregulin-β1 levels were further decreased in accordance with the severity of coronary artery lesions. Expression of heregulin-β1 was observed at trace levels in intracoronary atherothrombosis obtained by aspiration thrombectomy from acute coronary syndrome patients. Heregulin-β1, but not heregulin-, significantly reduced acetylated low-density lipoprotein–induced cholesterol ester accumulation in primary cultured human monocyte-derived macrophages by reducing SR-A and ACAT1 expression and by increasing ABCA1 expression at both mRNA and protein levels. Heregulin-β1 significantly decreased endocytic uptake of [125I]acetylated low-density lipoprotein and ACAT activity, and increased cholesterol efflux to apolipoprotein (Apo)A-I from human macrophages. Chronic infusion of heregulin-β1 into ApoE–/– mice significantly suppressed the development of atherosclerotic lesions.

Conclusions: This study provided the first evidence that heregulin-β1 inhibits atherogenesis and suppresses macrophage foam cell formation via SR-A and ACAT1 downregulation and ABCA1 upregulation.

  J Borg , C Klint , N Wierup , K Strom , S Larsson , F Sundler , R Lupi , P Marchetti , G Xu , A Kimmel , C Londos and C. Holm

Lipids have been shown to play a dual role in pancreatic β-cells: a lipid-derived signal appears to be necessary for glucose-stimulated insulin secretion, whereas lipid accumulation causes impaired insulin secretion and apoptosis. The ability of the protein perilipin to regulate lipolysis prompted an investigation of the presence of perilipin in the islets of Langerhans. In this study evidence is presented for perilipin expression in rat, mouse, and human islets of Langerhans as well as the rat clonal β-cell line INS-1. In rat and mouse islets, perilipin was verified to be present in β-cells. To examine whether the development of lipotoxicity could be prevented by manipulating the conditions for lipid storage in the β-cell, INS-1 cells with adenoviral-mediated overexpression of perilipin were exposed to lipotoxic conditions for 72 h. In cells exposed to palmitate, perilipin overexpression caused increased accumulation of triacylglycerols and decreased lipolysis compared with control cells. Whereas glucose-stimulated insulin secretion was retained after palmitate exposure in cells overexpressing perilipin, it was completely abolished in control β-cells. Thus, overexpression of perilipin appears to confer protection against the development of β-cell dysfunction after prolonged exposure to palmitate by promoting lipid storage and limiting lipolysis.

  Y Hu , B Tian , G Xu , L Yin , X Hua , J Lin and Y. Hua

The bacterium Deinococcus radiodurans is extremely resistant to the intense ionizing irradiation which causes extensive DNA double-strand breaks (DSBs). The deinococcal SbcCD complex (drSbcCD) is required for DSB repair. The drSbcC and drSbcD genes were cloned and overexpressed in Escherichia coli cells, respectively. The nearly homogeneous drSbcC and drSbcD proteins were purified and reconstituted to form a stable complex in vitro. The drSbcCD complex has an ATP-independent 3'->5' exonuclease activity to cleave both dsDNA and ssDNA substrates in the presence of either Mn2+ or Mg2+ ion. The drSbcCD complex also has an ATP-independent endonuclease activity. It can cleave the circular ssDNA, nick the supercoiled circular dsDNA, cleave the 3' flap DNA substrate at the site of the single-strand branch adjacent to duplex DNA, and cleave the hairpin DNA taking no account of the DNA end free or not. It is a kind of secondary structure-specific endonuclease. The drSbcCD complex still has a 3'->5' exonuclease activity when the DNA termini are blocked by the proteins. These results suggest that the drSbcCD complex takes part in the metabolism of DNA, and its nuclease activities may play important roles in DNA repair process.

  X Huang , X Bai , Y Cao , J Wu , M Huang , D Tang , S Tao , T Zhu , Y Liu , Y Yang , X Zhou , Y Zhao , M Wu , J Wei , D Wang , G Xu , S Wang , D Ma and J. Zhou

Angiogenesis is increasingly recognized as an important prognosticator associated with the progression of lymphoma and as an attractive target for novel modalities. We report a previously unrecognized mechanism by which lymphoma endothelium facilitates the growth and dissemination of lymphoma by interacting with circulated T cells and suppresses the activation of CD4+ T cells. Global gene expression profiles of microdissected endothelium from lymphoma and reactive lymph nodes revealed that T cell immunoglobulin and mucin domain–containing molecule 3 (Tim-3) was preferentially expressed in lymphoma-derived endothelial cells (ECs). Clinically, the level of Tim-3 in B cell lymphoma endothelium was closely correlated to both dissemination and poor prognosis. In vitro, Tim-3+ ECs modulated T cell response to lymphoma surrogate antigens by suppressing activation of CD4+ T lymphocytes through the activation of the interleukin-6–STAT3 pathway, inhibiting Th1 polarization, and providing protective immunity. In a lymphoma mouse model, Tim-3–expressing ECs promoted the onset, growth, and dissemination of lymphoma by inhibiting activation of CD4+ T cells and Th1 polarization. Our findings strongly argue that the lymphoma endothelium is not only a vessel system but also a functional barrier facilitating the establishment of lymphoma immune tolerance. These findings highlight a novel molecular mechanism that is a potential target for enhancing the efficacy of tumor immunotherapy and controlling metastatic diseases.

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