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Biomedical subjects

G Cheng

Publications and source records attributed to G Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2002

Antiproliferative activity of the extract of Gleditsia sinensis fruit on human solid tumour cell lines.

BACKGROUND: The fruit extract of Gleditsia sinensis Lam. (GSE) is a traditional herbal medicine that is saponin-rich. However, its activity on solid tumour cell lines has never been demonstrated. METHODS: The activity of GSE was demonstrated in four cancer cell lines (breast cancer MCF-7, MDA-MB231, hepatoblastoma HepG2 and oesophageal squamous carcinoma cell line SLMT-1) using MTT assay, anchorage-independent clonogenicity assay, DNA laddering and in situ cell death detection. RESULTS: The mean MTT(50) (the mean concentration of GSE to reduce MTT activity by 50%) ranged from 16 to 20 microg/ml of GSE. An anchorage-independent clonogenicity assay showed that all of the four solid tumour cell lines gradually lost their regeneration potential after treatment with GSE, DNA fragmentation and TUNEL analysis demonstrated that the action of GSE is both dose- and time course-dependent. CONCLUSIONS: Our results suggest that GSE has a cytotoxic activity and can induce apoptosis in human solid tumour cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Estrogen receptors and proliferation markers in primary and recurrent breast cancer.

To elucidate the clinical importance of estrogen receptor (ER) beta in breast cancer, 29 archival primary breast cancer specimens, six locally recurrent cancers, and five benign mammary tumors were examined histochemically for ERalpha, ERbeta and the proliferation markers Ki67 and cyclin A. In benign tumors, most epithelial cells contained ERbeta, but ERalpha was rare. In primary cancers, both ERalpha and ERbeta occurred in epithelial cells, the presence of ERbeta being associated with elevated expression of Ki67 and cyclin A, and ERalpha with decreased levels. Thus, the highest content of proliferation markers was seen in primary cancers that were ERalpha(-) ERbeta(+). Most Ki67-containing cells coexpressed ERbeta, but few showed ERalpha. In locally recurring cancers, ERalpha, ERbeta, and Ki67 were more highly expressed than in the corresponding primary tumors, and many cells containing ERbeta, but few with ERalpha, expressed Ki67. Surprisingly, ERbeta, but not ERalpha, was seen in the stromal cells of both primary and recurrent cancers. Because the response of breast cancers to tamoxifen therapy is correlated with the presence of ERalpha, cancer cells that lack ERalpha but contain ERbeta and proliferation markers represent a novel population of apparently proliferating cells that probably are not targeted by the current antiestrogens. Thus, appropriate ERbeta-specific ligands, perhaps in combination with tamoxifen, may be useful in improving the treatment of breast cancers.

Biomarkers, Tumor↗
PubMed2001

Val193 and Phe195 of the gamma 1 34.5 protein of herpes simplex virus 1 are required for viral resistance to interferon-alpha/beta.

Herpes simplex viruses (HSV) are resistant to the antiviral action of interferon. However, the underlying mechanisms are not well understood. In this report, we show that unlike that of wild-type HSV-1, replication of the gamma 1 34.5 null mutants was significantly inhibited by exogenous interferon-alpha in cells devoid of interferon-alpha/beta genes. Using a series of gamma 1 34.5 deletion mutants, the domain required for interferon resistance was mapped to the region containing amino acids 146 to 263 in the gamma 1 34.5 protein. Interestingly, Val193 Glu and Phe195 Leu substitutions in the protein phosphatase 1 interacting motif of the gamma 1 34.5 protein rendered HSV-1 sensitive to interferon-alpha. Furthermore, gamma 1 34.5 null mutants were sensitive to interferon-alpha/beta in PKR+/+ but not in PKR-/- mouse embryo fibroblasts. These findings provide evidence that the gamma 1 34.5 protein contributes to HSV-1 resistance to interferon-alpha/beta by inhibiting PKR function.

Amino Acids↗
PubMed2001

Inflammatory chemokine transport and presentation in HEV: a remote control mechanism for monocyte recruitment to lymph nodes in inflamed tissues.

Interstitial fluid is constantly drained into lymph nodes (LNs) via afferent lymph vessels. This conduit enables monocyte-derived macrophages and dendritic cells to access LNs from peripheral tissues. We show that during inflammation in the skin, a second recruitment pathway is evoked that recruits large numbers of blood-borne monocytes to LNs via high endothelial venules (HEVs). Inhibition of monocyte chemoattractant protein (MCP)-1 blocked this inflammation-induced monocyte homing to LNs. MCP-1 mRNA in inflamed skin was over 100-fold upregulated and paralleled MCP-1 protein levels, whereas in draining LNs MCP-1 mRNA induction was much weaker and occurred only after a pronounced rise in MCP-1 protein. Thus, MCP-1 in draining LNs was primarily derived from inflamed skin. In MCP-1(-/-) mice, intracutaneously injected MCP-1 accumulated rapidly in the draining LNs where it enhanced monocyte recruitment. Intravital microscopy showed that skin-derived MCP-1 was transported via the lymph to the luminal surface of HEVs where it triggered integrin-dependent arrest of rolling monocytes. These findings demonstrate that inflamed peripheral tissues project their local chemokine profile to HEVs in draining LNs and thereby exert "remote control" over the composition of leukocyte populations that home to these organs from the blood.

Adoptive Transfer↗
PubMed2001

Enhanced sensitivity to apoptosis in Ras-transformed thyroid cells.

Ras mutations occur at high frequency in thyroid cancer. In vitro, the effects of Ras in thyroid cells are pleiotropic in that expression of activated Ras has been reported to stimulate proliferation and apoptosis. An understanding of the factors that contribute to the survival versus demise of Ras-transformed cells is essential to our understanding of the contribution of Ras to thyroid neoplasia and other cancers. Constitutive expression of oncogenic H-Ras sensitized Wistar rat thyroid (WRT) cells to apoptosis stimulated by multiple insults. When deprived of matrix attachment, Ras-transformed cells perished by apoptotic cell death at a high frequency. In contrast, parental cells were more resistant to suspension-induced cell death. Ras effects on anchorage-independent cell death were reproduced by a mutant protein that signals selectively to Raf-1, but not by mutant Ras that preferentially binds to RalGDS. Expression of a Ras mutant that selectively activates PI3K resulted in substantial protection from detachment-induced cell death. MAPK activity was increased in adherent Ras12V- and Ras12V35S-expressing cells, but abolished upon detachment. Interestingly, impaired MAPK activity was sufficient to stimulate apoptosis in adherent Ras-transformed cells, but not in parental cells. Treatment with a PI3K inhibitor also stimulated apoptosis selectively in Ras-transformed cells. These results demonstrate that constitutive expression of activated Ras elicits differential effects on the survival of thyroid cells. Moreover, Ras expression results in a greater dependence of thyroid cells on MAPK and PI3K activity for their survival.

Amino Acid Substitution↗
PubMed2001

Signaling lymphocytic activation molecule is expressed on CD40 ligand-activated dendritic cells and directly augments production of inflammatory cytokines.

Dendritic cells (DC) comprise a key part of the innate immune system that, upon activation, profoundly influences the nature of the adaptive T cell response. In this study, we present evidence that signaling lymphocytic activation molecule (SLAM), a molecule first identified in activated T and B cells, is strongly up-regulated in DC activated through CD40, as well as in response to inflammatory stimuli, including polyinosinic polycytidylic acid and LPS. mRNA encoding both membrane-bound and soluble secreted isoforms of SLAM was detected in CD40 ligand-activated DC, comprising two of the four known SLAM isoforms. Expression of membrane-bound SLAM protein peaked at 12 h poststimulation with CD40 ligand, gradually returning to baseline levels after 6 days. SLAM up-regulation appears to be a direct result of the induction of DC maturation, as inflammatory cytokines released during this process do not affect SLAM expression. Functionally, engagement of SLAM enhances DC production of IL-12 and IL-8, while having no effect on production of IL-10. Because SLAM is involved in the activation of T cells, the expression of SLAM on DC may provide a bidirectional signaling mechanism in which interacting DC and T cells are simultaneously and synergistically activated to mount proinflammatory Th1 responses.

Adult↗
PubMed2001

Tyrosine cross-linking of extracellular matrix is catalyzed by Duox, a multidomain oxidase/peroxidase with homology to the phagocyte oxidase subunit gp91phox.

High molecular weight homologues of gp91phox, the superoxide-generating subunit of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, have been identified in human (h) and Caenorhabditis elegans (Ce), and are termed Duox for "dual oxidase" because they have both a peroxidase homology domain and a gp91phox domain. A topology model predicts that the enzyme will utilize cytosolic NADPH to generate reactive oxygen, but the function of the ecto peroxidase domain was unknown. Ce-Duox1 is expressed in hypodermal cells underlying the cuticle of larval animals. To investigate function, RNA interference (RNAi) was carried out in C. elegans. RNAi animals showed complex phenotypes similar to those described previously in mutations in collagen biosynthesis that are known to affect the cuticle, an extracellular matrix. Electron micrographs showed gross abnormalities in the cuticle of RNAi animals. In cuticle, collagen and other proteins are cross-linked via di- and trityrosine linkages, and these linkages were absent in RNAi animals. The expressed peroxidase domains of both Ce-Duox1 and h-Duox showed peroxidase activity and catalyzed cross-linking of free tyrosine ethyl ester. Thus, Ce-Duox catalyzes the cross-linking of tyrosine residues involved in the stabilization of cuticular extracellular matrix.

Amino Acid Sequence↗
PubMed2001

Controlled nucleation and growth of surface-confined gold nanoparticles on a (3-aminopropyl)trimethoxysilane-modified glass slide: a strategy for SPR substrates.

The thickness of the gold film and its morphology, including the surface roughness, are very important for getting a good, reproducible response in the SPR technique. Here, we report a novel alternative approach for preparing SPR-active substrates that is completely solution-based. Our strategy is based on self-assembly of the gold colloid monolayer on a (3-aminopropyl)trimethoxysilane-modified glass slide, followed by electroless gold plating. Using this method, the thickness of films can be easily controlled at the nanometer scale by setting the plating time in the same conditions. Surface roughness and morphology of gold films can be modified by both tuning the size of gold nanoparticles and agitation during the plating. Surface evolution of the Au film was followed in real time by UV-vis spectroscopy and in situ SPRS. To assess the surface roughness and electrochemical stability of the Au films, atomic force microscopy and cyclic voltammetry were used. In addition, the stability of the gold adhesion is demonstrated by three methods. The as-prepared Au films on substrates are reproducible and stable, which allows them to be used as electrodes for electrochemical experiments and as platforms for studying SAMs.

Journal Article↗
PubMed2001

Homologs of gp91phox: cloning and tissue expression of Nox3, Nox4, and Nox5.

gp91phox is the catalytic subunit of the respiratory burst oxidase, an NADPH-dependent, superoxide generating enzyme present in phagocytes. In phagocytes, the enzyme functions in host defense, but reactive oxygen generation has also been described in a variety of non-phagocytic cells, including cancer cells. We previously reported the cloning of Nox1 (NADPH oxidase1), a homolog of gp91phox, its expression in colon and vascular smooth muscle, and its oncogenic properties when overexpressed [Suh et al. (1999). Nature 401, 79-82]. Herein, we report the cloning and tissue expression of three additional homologs of gp91phox, termed Nox3, Nox4 and Nox5, members of a growing family of gp91phox homologs. All are predicted to encode proteins of around 65 kDa, and like gp91phox, all show 5-6 conserved predicted transmembrane alpha-helices containing putative heme binding regions as well as a flavoprotein homology domain containing predicted binding sites for both FAD and NADPH. Nox3 is expressed primarily in fetal tissues, and Nox4 is expressed in not only fetal tissues, but also kidney, placenta and glioblastoma cells. Nox5 is expressed in a variety of fetal tissues as well as in adult spleen and uterus. Nox isoforms are aberrantly expressed in several cells derived from human cancers, with Nox4 being the isoform most frequently expressed in the tumor cells investigated. Thus, expression of Nox family members is likely to account for some of the reactive oxygen generation seen in non-phagocytic cells.

Amino Acid Sequence↗
PubMed2001

Requirements for activation and RAFT localization of the T-lymphocyte kinase Rlk/Txk.

BACKGROUND: The Tec family kinases are implicated in signaling from lymphocyte antigen receptors and are activated following phosphorylation by Src kinases. For most Tec kinases, this activation requires an interaction between their pleckstrin homology (PH) domains and the products of phosphoinositide 3-Kinase, which localizes Tec kinases to membrane RAFTs. Rlk/Txk is a Tec related kinase expressed in T cells that lacks a pleckstrin homology domain, having instead a palmitoylated cysteine-string motif. To evaluate Rlk's function in T cell receptor signaling cascades, we examined the requirements for Rlk localization and activation by Src family kinases. RESULTS: We demonstrate that Rlk is also associated with RAFTs, despite its lack of a pleckstrin homology domain. Rlk RAFT association requires the cysteine-string motif and is independent of PI3 Kinase activity. We further demonstrate that Rlk can be phosphorylated and activated by Src kinases, leading to a decrease in its half-life. A specific tyrosine in the activation loop of Rlk, Y420, is required for phosphorylation and activation, as well as for decreased stability, but is not required for lipid RAFT association. Mutation of this tyrosine also prevents increased tyrosine phosphorylation of Rlk after stimulation of the T cell receptor, suggesting that Rlk is phosphorylated by Src family kinases in response to T cell receptor engagement. CONCLUSIONS: Like the other related Tec kinases, Rlk is associated with lipid RAFTs and can be phosphorylated and activated by Src family kinases, supporting a role for Rlk in signaling downstream of Src kinases in T cell activation.

Cell Line↗
PubMed2001

The electrochemically induced conformational transition of disulfides in bovine serum albumin studied by thin layer circular dichroism spectroelectrochemistry.

The conformational transition of disulfides in bovine serum albumin (BSA) induced by electrochemical redox reaction of disulfides were monitored by in-situ circular dichroism (CD) spectroelectrochemistry, with a long optical path thin layer cell and analyzed by a singular value decomposition least square (SVDLS) method. Electrochemical reduction of disulfides drives the left-handed conformation of disulfides changed into the right-handed. At open circuit, eight of the 17 disulfides were of left-handed conformation. Four of the 17 disulfides took part in the electrochemical reduction with an EC mechanism. Only one-fourth of the reduced disulfides returned to left-handed conformation in the re-oxidation process. Some parameters of the electrochemical reduction process, i.e. the number of electrons transferred and electron transfer coefficient, n = 8, alpha n = 0.15, apparent formal potential, E1(0') = -0.65(+/-0.01) V, standard heterogeneous electron transfer rate constant, k1(0) = (2.84 +/- 0.14) x 10(-5) cm s(-1) and chemical reaction equilibrium constant, Kc = (5.13 +/- 0.12) x 10(-2), were also obtained by double logarithmic analysis based on the near-UV absorption spectra with applied potentials.

Algorithms↗
PubMed2001

Transfusion of peripheral blood stem cells from donor homozygous for a shared HLA-haplotype: avoiding fatal transfusion-associated graft-versus-host disease while preserving anti-leukemic effect.

BACKGROUND: Fatal transfusion-associated graft-versus-host disease was observed in immunocompetent patients transfused with blood from donors homozygous for a shared haplotype with the recipient (the P-F1 barrier). We tested whether it was possible to carry out successful transplantation in a patient with relapsed acute myeloid leukemia, using peripheral blood stem cells from his HLA-homozygous brother (HLA A2, B46, DRB1 901) who shared a haplotype with the patient (HLA A2, B46,75, DRB1 901,12). METHODS: A CD34 positively selected cell fraction (5.46x 10(6) CD34 cells/kg) was infused first, followed by subsequent infusion of graded doses of donor T cells (total 7.25x10(7) T cells/kg). Nonmyeloablative chemotherapy with idarubicin and cytarabine was given during the transplantation to reduce the leukemic burden and facilitate engraftment. Polymerase chain reaction with the VNTR primers, D1S80, was used to detect engraftment. RESULTS: Complete remission (>300days) and successful donor engraftment (90%) were achieved. CONCLUSIONS: Peripheral blood stem cells transplantation from a donor with a homozygous shared haplotype is possible with a minimal preparative regimen.

Acute Disease↗
PubMed2001

Interleukin (IL)-4/IL-9 and exogenous IL-16 induce IL-16 production by BEAS-2B cells, a bronchial epithelial cell line.

Previous studies have suggested that bronchial epithelial cells may perpetuate airway inflammation. We have reported that the bronchial epithelial cell line BEAS-2B can produce interleukin (IL)-16, a potent chemoattractant for CD4+ T cells. IL-16 is thought to regulate airway inflammation in asthmatics. Recent studies showed that IL-4 induces inflammatory cytokines in bronchial epithelial cells and that IL-9 is a candidate gene for development of asthma. The present study demonstrated that BEAS-2B cells produced specifically IL-16 by synergistic effects of IL-4 + IL-16, or IL-9 + IL-16, and that the synthesized IL-16 induced migration of CD4+ T cells. This study is a first report indicating that IL-16 production may be maintained by an autocrine machinery by epithelial cell-derived IL-16 with IL-4 and IL-9 in asthma.

Bronchi↗
PubMed2001

To err is human nature. Can transfusion errors due to human factors ever be eliminated?

BACKGROUND: Fatal hemolytic transfusion reaction due to ABO incompatibility occurs mainly as a result of clerical errors. Blood sample drawn from the wrong patient and labeled as another patient's specimen will not be detected by the blood bank unless there is a previous ABO grouping result. METHODS: In Hong Kong, we had designed a transfusion wristband system--portable barcode scanner system to detect such clerical errors. The system was well accepted by the house staff and had prevented two BO mismatched transfusion. Other current system of patient's identification may have similar results, but the wristband system has the advantages of being simple, inexpensive and easy to implement. The Hong Kong Government is planning to replace the personal identity card for all citizens with an electronic smart card by 2003. If the new card contains the person's detailed red cell phenotypes in digital code, then the phenotypes of all blood donors and admitted patients will be readily available. It is feasible to issue phenotype-matched blood to patients without any need of pre-transfusion testing, therefore eliminating mismatched transfusions for most patients. RESULTS: Our pilot study of 474 patients showed that the system was safe and up to 98% of admitted patients could be transfused without delays. CONCLUSIONS: Patients with rare phenotypes, visitors or illegal immigrants may still need pre-transfusion antibody screen, but if most patients can be issued blood units without testings, the potential savings in health care amount to US$14 million/year.

ABO Blood-Group System↗
PubMed2001

The alpha(1,3)fucosyltransferases FucT-IV and FucT-VII exert collaborative control over selectin-dependent leukocyte recruitment and lymphocyte homing.

E-, P-, and L-selectin counterreceptor activities, leukocyte trafficking, and lymphocyte homing are controlled prominently but incompletely by alpha(1,3)fucosyltransferase FucT-VII-dependent fucosylation. Molecular determinants for FucT-VII-independent leukocyte trafficking are not defined, and evidence for contributions by or requirements for other FucTs in leukocyte recruitment is contradictory and incomplete. We show here that inflammation-dependent leukocyte recruitment retained in FucT-VII deficiency is extinguished in FucT-IV(-/-)/FucT-VII(-/-) mice. Double deficiency yields an extreme leukocytosis characterized by decreased neutrophil turnover and increased neutrophil production. FucT-IV also contributes to HEV-born L-selectin ligands, since lymphocyte homing retained in FucT-VII(-/-) mice is revoked in FucT-IV(-/-)/FucT-VII(-/-) mice. These observations reveal essential FucT-IV-dependent contributions to E-, P-, and L-selectin ligand synthesis and to the control of leukocyte recruitment and lymphocyte homing.

Animals↗