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Biomedical subjects

Jun Guo

Publications and source records attributed to Jun Guo.

At least 73 records · Page 4Linked to original sources
PubMed2004

Intratumoral expression of MIP-1beta induces antitumor responses in a pre-established tumor model through chemoattracting T cells and NK cells.

Direct intratumoral introduction of therapeutic or regulatory genes is a developing technology with potential application for cancer gene therapy. Macrophage inflammatory protein-1 beta (MIP-1beta) is a chemokine which can chemoattract immune cells such as T cells. In the present study, murine colorectal adenocarcinoma CT26 cells were transfected with a recombinant adenovirus (AdhMIP-1beta) carrying the human MIP-1beta gene. 24 h post-transfection, hMIP-1beta levels reached approximately 980 pg/ml in supernatants of 10(6) hMIP-1beta-transfected CT26 cells. Moreover, the supernatants exhibited chemotactic activity for CD8(+) T cells, CD4(+) T cells, NK cells and immature DCs. Intratumoral injection of AdhMIP-1beta significantly inhibited tumor growth and prolonged the survival time of tumor-bearing mice. Intratumoral hMIP-1beta gene transfer also induced powerful tumor-specific CTL responses in vivo. The therapeutic effects of hMIP-1beta gene therapy were greatly reduced following in vivo depletion of both CD4(+) and CD8(+) T cells, but were unaffected by depletion of single T cell subsets. Immune cell depletion experiments also revealed that NK cells played an important role in hMIP-1beta-induced antitumor responses. These results suggest that intratumoral expression of hMIP-1beta has the potential effect to induce host antitumor immunity and may prove to be a useful form of cancer gene therapy.

Adenocarcinoma↗
PubMed2003

Heterocyclic ketones as inhibitors of histone deacetylase.

Several heterocyclic ketones were investigated as potential inhibitors of histone deacetylase. Nanomolar inhibitors such as 22 and 25 were obtained, the anti-proliferative activity of which were shown to be mediated by HDAC inhibition.

Enzyme Inhibitors↗
PubMed2003

Chemoattraction, adhesion and activation of natural killer cells are involved in the antitumor immune response induced by fractalkine/CX3CL1.

Fractalkine (FK, also called neurotactin or CX3CL1) is a CX3C chemokine that can chemoattract T lymphocytes, monocytes, dendritic cells (DC) and natural killer (NK) cells. One of our previous studies demonstrated that FK in soluble form can chemoattract T cells and DC and membrane-bound FK can adhere T cells and DC. Vaccination with 3LL lung carcinoma cells gene-modified with FK (3LL-FK) induces potent antitumor CTL response. The aim of the present study is to investigate whether NK cells participate in FK-induced antitumor immunity. We found that NK activity was increased in mice inoculated with 3LL-FK and in vivo depletion of NK cells resulted in the decreased tumor growth inhibition of 3LL-FK, indicating that NK cells play an important role in the antitumor immunity induced by FK. Further studies showed 3LL-FK could chemoattract, adhere NK cells and attract more NK cells to infiltrate into tumor tissue. Incubation of NK cells with 3LL-FK could increase the cytotoxicity of NK cells against YAC-1 cells and even against NK-resistant parental 3LL cells. IL-12 production increased more significantly in the 3LL-FK tumor nodules. Taken together with CTL response induced by 3LL-FK, our data demonstrate that FK, expressed by gene-modified tumor cells, can induce potent antitumor effect through different mechanisms, one of which involves chemoattraction of NK cells into tumor sites and activation of NK cells.

Animals↗
PubMed2003

Cerebral ischemia immediately increases serine phosphorylation of the synaptic RAS-GTPase activating protein SynGAP by calcium/calmodulin-dependent protein kinase II alpha in hippocampus of rats.

The interaction between translocated calcium/calmdulin-dependent protein kinase IIalpha (CaMK IIalpha) and SynGAP during brain ischemia was investigated by Western blotting and immunoprecipitation. Brain ischemia was induced by the four-vessel occlusion method on Sprague-Dawley rats. After 3 min global ischemia, both the binding of CaMK IIalpha to SynGAP and the serine phosphorylation of SynGAP all dramatically increased. Administrating KN-62 through cerebral ventricle (20 min before ischemia) not only remarkably decreased the binding of CaMK IIalpha to SynGAP but also attenuate the elevated serine phosphorylation of SynGAP following 20 min ischemia in hippocampus. These results suggest that CaMK IIalpha is responsible for the serine phosphorylation of SynGAP and a consequent phosphorylation and inhibition of SynGAP may result in activation of mitogen-activated protein kinase pathway which could serve a protective function in brain ischemia.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2003

Alpha-keto amides as inhibitors of histone deacetylase.

Alpha-keto ester and amides were found to be potent inhibitors of histone deacetylase. Nanomolar inhibitors against the isolated enzyme and sub-micromolar inhibitors of cellular proliferation were obtained. The alpha-keto amide 30 also exhibited significant anti-tumor effects in an in vivo tumor model.

Amides↗
PubMed2003

Cyclosporin A impairs dendritic cell migration by regulating chemokine receptor expression and inhibiting cyclooxygenase-2 expression.

Migration of dendritic cells (DCs) into tissues and secondary lymphoid organs plays a crucial role in the initiation of innate and adaptive immunity. In this article, we show that cyclosporin A (CsA) impairs the migration of DCs both in vitro and in vivo. Exposure of DCs to clinical concentrations of CsA neither induces apoptosis nor alters development but does impair cytokine secretion, chemokine receptor expression, and migration. In vitro, CsA impairs the migration of mouse bone marrow-derived DCs toward macrophage inflammatory protein-3beta (MIP-3beta) and induces them to retain responsiveness to MIP-1alpha after lipopolysaccharide (LPS)-stimulated DC maturation, while in vivo administration of CsA inhibits the migration of DCs out of skin and into the secondary lymphoid organs. CsA impairs chemokine receptor and cyclooxygenase-2 (COX-2) expression normally triggered in LPS-stimulated DCs; administration of exogenous prostaglandin E2 (PGE2) reverses the effects of CsA on chemokine receptor expression and DC migration. Inhibition of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK) pathway signaling by CsA may be responsible for the CsA-mediated effects on the regulation of chemokine receptor and cyclooxygenase-2 (COX-2) expression. Impairment of DC migration due to inhibition of PGE2 production and regulation of chemokine receptor expression may contribute, in part, to CsA-mediated immunosuppression.

Animals↗
PubMed2003

Fas ligation induces IL-1beta-dependent maturation and IL-1beta-independent survival of dendritic cells: different roles of ERK and NF-kappaB signaling pathways.

The mechanisms that underpin the intriguing capacity of Fas ligation on dendritic cells (DCs) to induce maturation and activation, rather than apoptosis, remain unclear. In the present study we confirm that Fas signaling induces both phenotypic and functional maturation of murine DCs, and we demonstrate that phenotypic maturation is associated with phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, activation of caspase-1, and secretion of interleukin-beta (IL-1beta). Specific inhibition of ERK1/2 diminished Fas ligation-induced caspase-1 activation, IL-1beta secretion, and ensuing up-regulation of developmental markers, whereas treatment with neutralizing anti-IL-1beta antibody abrogated phenotypic and functional maturation, indicating that IL-1beta mediates Fas ligation-induced DC maturation in an autocrine manner. NF-kappaB activation was responsible for maintaining DC viability after Fas ligation. Inhibiting NF-kappaB did not affect either IL-1beta secretion or phenotypic maturation but rather sensitized DCs to Fas-mediated apoptosis. In conclusion, positive signals originating from Fas are transduced through at least 2 different intracellular pathways in DCs, promoting not only survival but also an increase in maturation that correlates with increased antigen-presentation capability.

Animals↗
PubMed2003

Free radicals are involved in continuous activation of nonreceptor tyrosine protein kinase c-Src after ischemia/reperfusion in rat hippocampus.

NMDA receptor-mediated calcium over-loading and the following free radical generation play essential roles in cerebral ischemia lesion, leading to neuronal cell apoptosis or necrosis through complicated intracellular signaling cascades. Here we evaluated the effects of NMDA receptor antagonist (ketamine) and antioxidant (N-acetylcysteine) on ischemia- and reperfusion-induced activation of tyrosine kinase c-Src. The in vitro kinase assay showed that the ischemia-induced rapid activation of c-Src reached its peak at 5 min, and the reperfusion-induced continuous activation of c-Src reached another peak at 6 h reperfusion after 15 min ischemia (4.2 and 3.0 fold vs. sham control, respectively). Ketamine might suppress both peaks described above, but N-acetylcysteine, a free radical scavenger, was only able to partly reduce the peak activation elicited by 6 h reperfusion. These results suggest that free radical production is involved in NMDA receptor-mediated continuous activation of c-Src during ischemia/reperfusion but not that during ischemia.

Acetylcysteine↗
PubMed2003

Indole amide hydroxamic acids as potent inhibitors of histone deacetylases.

A series of hydroxamic acid-based HDAC inhibitors with an indole amide residue at the terminus have been synthesized and evaluated. Compounds with a 2-indole amide moiety have been found as the most active inhibitors among the different regioisomers. Introduction of substituents on the indole ring further improved the potency and generated a series of very potent inhibitors with significant antiproliferative activity. A representative compound in the series, 7b, has been found to be orally active in tumor growth inhibition model.

Amides↗
PubMed2003

Rab39, a novel Golgi-associated Rab GTPase from human dendritic cells involved in cellular endocytosis.

Rab GTPases are Ras-like small molecular weight GTP binding proteins that are involved in various steps along the exocytic and endocytic pathways. Here we report that Rab39, a novel Rab protein, is a Golgi-associated protein involved in endocytosis of HeLa cells. Full-length cDNA of Rab39 contains 1251bp with an open reading frame (ORF) of 636bp, which is predicted to encode a 211 aa protein. By blast analysis of Rab39 cDNA and protein sequence with homologues, we find that Rab39 may be a short variant of Rab34. Rab39 contains conserved motifs involved in phosphate/guanosine binding and a microbody C-terminal targeting signal. RT-PCR analysis indicates that Rab39 is mainly detected in epithelial cell lines, and Northern blot analysis shows that Rab39 is expressed ubiquitously in human tissues. By using FITC-BSA as an endocytic tracer, we show that Rab39 can facilitate endocytosis in HeLa cells when expressed either transiently or stably. Confocal microscopy examination of Rab39 subcellular localization suggests that Rab39 is associated with Golgi-associated organelles. Our findings demonstrate that Rab39 is a novel Rab GTPase involved in cellular endocytosis.

3T3 Cells↗
PubMed2003

Autophosphorylated calcium/calmodulin-dependent protein kinase II alpha (CaMKII alpha) reversibly targets to and phosphorylates N-methyl-D-aspartate receptor subunit 2B (NR2B) in cerebral ischemia and reperfusion in hippocampus of rats.

It has been reported that cerebral ischemia induces Thr286 autophosphorylation and translocation of CaMKIIalpha which targets to and phosphorylates NR2B in hippocampus of rats [Neuroscience 96 (2000) 665; J. Biol. Chem. 275 (2000) 23798]. To further illustrate the mechanisms underlying these processes, we examined the effects of ketamine (a selective antagonist of NMDA receptor), KN-62 (1-[N,O-bis-(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine, a selective inhibitor of CaMKII) and reperfusion on CaMKII and NMDA receptors and the interactions between these signal proteins. Firstly, our results showed that ketamine decreased the ischemia-induced autophosphorylation, translocation and the targeting of CaMKIIalpha to NR2B and the serine-phosphorylation of NR2B. Secondly, KN-62 also inhibited the autophosphorylation of CaMKIIalpha, NR2B serine-phosphorylation and the binding of CaMKIIalpha to NR2B but had no effect on the translocation of CaMKII. These data strongly suggest that NMDA receptor channels mediated the Ca(2+)-dependent activation of CaMKII and NMDA receptors surely were the substrates on membranes of active CaMKII. Thirdly, our results indicated the concomitant phosphorylation and dephosphorylation of CaMKII and NR2B following ischemia or longer reperfusion. Moreover, the dissociation of CaMKII from NR2B had the same trend as that of the return of CaMKII to cytosol. All these data imply the close relationships between CaMKII and NR2B during ischemia and reperfusion, namely, CaMKII might act as an amplifier of detrimental cellular calcium signal regulated by NMDA receptors when becoming autophosphorylated and targeting to NR2B; conversely, autophosphorylated CaMKII could modulate NMDA receptor channel properties by phosphorylating NR2B.

Animals↗
PubMed2003

Phosphatidylinositol 4-kinase type IIalpha is responsible for the phosphatidylinositol 4-kinase activity associated with synaptic vesicles.

Phosphorylation of inositol phospholipids plays a key role in cellular regulation via the generation of intracellular second messengers. In addition, it represents a mechanism to regulate interactions of the lipid bilayer with proteins and protein scaffolds involved in vesicle budding, cytoskeletal organization, and signaling. Generation of phosphatidylinositol 4-phosphate [PI(4)P] from phosphatidylinositol (PI) is an important step in this metabolic pathway because PI(4)P is a precursor of other important phosphoinositides and has protein binding properties of its own. We report here that a PI 4-kinase (PI4K) activity previously reported on synaptic vesicles is accounted for by the alpha isoform of the recently characterized type II PI4K (PI4KII) family. PI4KIIalpha, which also accounts for the bulk of PI4K activity in brain extracts, is concentrated at synapses and in the region of the Golgi complex in neuronal perikarya. Our results provide new evidence for the occurrence of a cycle of phosphoinositide synthesis and hydrolysis nested within the exo-endocytic cycle of synaptic vesicles and point to PI4KIIalpha as a critical player in this cycle.

1-Phosphatidylinositol 4-Kinase↗
PubMed2003

Fractalkine transgene induces T-cell-dependent antitumor immunity through chemoattraction and activation of dendritic cells.

Fractalkine (FK, also called neurotactin or CX3CL1) is a CX3C chemokine that can chemoattract T lymphocytes, monocytes and NK cells. In our study, we investigated the induction of antitumor response by FK gene transfer. FK gene-modified 3LL lung carcinoma cells (3LL-FK) could both secrete soluble form and express membrane-bound form of FK. The tumor growth of 3LL-FK was decreased. Vaccination with 3LL-FK was effective in the induction of protective immunity and CTL. In vivo depletion analysis demonstrated that CD8(+) T cells are the main participating cells of the antitumor response. Obvious infiltrations of CD8(+) T cells, CD4(+) T cells and dendritic cells (DC) were observed in the tumor sites, suggesting that 3LL-FK might induce antitumor immunity through chemoattraction and activation of T cells and DC. Then we investigated the chemoattraction and activation of DC by 3LL-FK. Chemotaxis assay showed that the supernatants of 3LL-FK could chemoattract immature DC, which were found to express FK receptor CX3CR1, and the immature DC could obviously adhere to 3LL-FK. Adherence of DC to 3LL-FK resulted in phenotypic maturation and upregulated IL-12 secretion of DC, and more strong stimulation of allogeneic T-cell proliferation by DC. The increased production of IL-2 and IFNgamma in 3LL-FK tumor tissue was also observed. Our data suggested that FK gene transfer to tumor cells could induce T-cell-dependent antitumor immunity through chemoattraction and activation of DC.

Animals↗
PubMed2003

Methylation of SPT5 regulates its interaction with RNA polymerase II and transcriptional elongation properties.

SPT5 and its binding partner SPT4 function in both positively and negatively regulating transcriptional elongation. The demonstration that SPT5 and RNA polymerase II are targets for phosphorylation by CDK9/cyclin T1 indicates that posttranslational modifications of these factors are important in regulating the elongation process. In this study, we utilized a biochemical approach to demonstrate that SPT5 was specifically associated with the protein arginine methyltransferases PRMT1 and PRMT5 and that SPT5 methylation regulated its interaction with RNA polymerase II. Specific arginine residues in SPT5 that are methylated by these enzymes were identified and demonstrated to be important in regulating its promoter association and subsequent effects on transcriptional elongation. These results suggest that methylation of SPT5 is an important posttranslational modification that is involved in regulating its transcriptional elongation properties in response to viral and cellular factors.

Arginine↗
PubMed2003

The rat sodium iodide symporter gene permits more effective radioisotope concentration than the human sodium iodide symporter gene in human and rodent cancer cells.

Expression of the sodium iodide symporter (NIS) gene in tumor cells may provide a novel mechanism for treating cancer. The NIS mediates the normal physiological transport of iodide across the thyroid cell membrane. This mechanism of iodide uptake has been used to both diagnose and treat thyroid cancer. Tissue expression of the NIS is largely limited to the thyroid; therefore, expression of the NIS gene in cancer cells would allow for specific iodine uptake, radioisotope accumulation, and treatment. In this study, we directly compared the human and rat NIS (rNIS) for their ability to concentrate radioisotope into human and rodent cancer cells. Perchlorate-sensitive (125)I uptake in multiple cell lines was demonstrated following transduction with retroviral vectors expressing either the human or rNIS gene. Surprisingly, iodine uptake was consistently higher with the rNIS gene, up to 5-fold greater, when compared to the human gene, even within a variety of human tumor cell lines. This iodine uptake allowed for cell killing following (131)I treatment in NIS-transduced cells when assayed by in vitro clonogenic assays. These results demonstrate that the rNIS gene provides superior iodine uptake ability, and may be preferable for use in designing anticancer gene therapy approaches.

Animals↗
PubMed2003

Loss of function and impaired degradation of a cataract-associated mutant connexin50.

A mutant human connexin50 (hCx50), hCx50P88S, has been linked to cataracts inherited as an autosomal dominant trait. The functional, biochemical and cellular behavior of wild-type and mutant hCx50 were examined in transfected cells. hCx50P88S was unable to induce gap junctional currents by itself, and it abolished gap junctional currents when co-expressed with wild-type (wt) hCx50. Cells transfected with hCx50P88S showed cytoplasmic accumulations of Cx50 immunoreactivity in addition to staining at appositional membranes; these accumulations did not significantly co-localize with markers for the endoplasmic reticulum, Golgi apparatus, lysosomes, endosomes or vimentin filaments. Immunoelectron microscopy studies localized hCx50P88S to cytoplasmic membrane stacks in close vicinity to the endoplasmic reticulum. In contrast, aggresome-like accumulations were induced by treatment of wt hCx50-transfected cells with proteasomal inhibitors. The formation of hCx50P88S accumulations in transiently transfected cells was not blocked by treatment with Brefeldin A suggesting that they form before Cx50 transits through the Golgi apparatus to the plasma membrane. Treatment of HeLa-hCx50P88S cells with cycloheximide demonstrated the presence of a very stable pool of hCx50P88S. Taken together, these results suggest that the P to S mutation at amino acid residue 88 causes a defect that leads to decreased degradation and subsequent accumulation of hCx50P88S in a cellular structure different from aggresomes.

Animals↗
PubMed2003

[Investigation of apoptosis mechanism of arsenic trioxide on oral squamous cell carcinoma].

OBJECTIVE: To probe the possible mechanism of growth-inhibitory and apoptosis of oral squamous cell carcinoma by arsenic trioxide. METHODS: The induction of apoptosis in two tongue squamous carcinoma cells treated by arsenic trioxide was investigated. The morphology changes of the cells was observed under electron microscope. The mitochondrial transmembrane potential was detected using rhodamine 123 and flow cytometry. The cell cycle was detected by flow cytometry, and p16, p53, BCL-2, Caspase-3, and PARP changes were examined by western blot. RESULTS: 1. The antiproliferative effect on the oral squamous carcinoma cells by arsenic trioxide was carried out through two ways: induction of apoptosis and toxicity damage. 2. Activation of the caspase-3 and PARP, while no changes of p16, p53, BCL-2 occurred. 3. Mitochondrial transmembrane potential collapse and G(2)-M stagnation were correlated with apoptosis of oral squamous cell carcinoma. CONCLUSIONS: 1. Tubulins and mitochondria may be the chief action position of arsenic trioxide, which is the start-up factors of mechanism. 2. Activation of the caspase-3 proteolytic pathway may be one of the pivotal ways of apoptosis procedure induced by arsenic trioxide.

Antineoplastic Agents↗