Biomedical subjects

Yufang Wang

Publications and source records attributed to Yufang Wang.

10 recordsLinked to original sources

PubMed2006

The effects of a novel MEK inhibitor PD184161 on MEK-ERK signaling and growth in human liver cancer.

The MEK-ERK growth signaling pathway is important in human hepatocellular carcinoma (HCC). To evaluate the targeting of this pathway in HCC, we characterized a novel, orally-active MEK inhibitor, PD184161, using human HCC cells (HepG2, Hep3B, PLC, and SKHep) and in vivo human tumor xenografts. PD184161 inhibited MEK activity (IC50 = 10-100 nM) in a time- and concentration-dependent manner more effectively than PD098059 or U0126. PD184161 inhibited cell proliferation and induced apoptosis at concentrations of > or = 1.0 microM in a time- and concentration-dependent manner. In vivo, tumor xenograft P-ERK levels were significantly reduced 3 to 12 hours after an oral dose of PD184161 (P < .05). Contrarily, tumor xenograft P-ERK levels following long-term (24 days) daily dosing of PD184161 were refractory to this signaling effect. PD184161 significantly suppressed tumor engraftment and initial growth (P < .0001); however, established tumors were not significantly affected. In conclusion, PD184161 has antitumor effects in HCC in vitro and in vivo that appear to correlate with suppression of MEK activity. These studies demonstrate that PD184161 is unable to suppress MEK activity in HCC xenografts in the long term. Thus, we speculate that the degree of success of MEK targeted treatment in HCC and other cancers may, in part, depend on the discovery of mechanisms governing MEK inhibitor signaling resistance.

Aniline Compounds↗

PubMed2005

Speeding up a single-molecule DNA device with a simple catalyst.

Recently, several groups have designed and synthesized single-molecule devices based on DNA that can switch between different configurations in response to sequential addition of fuel DNA strands. There is considerable interest in improving the speed of these "nanomotors." One approach is the use of rationally designed DNA catalysts to promote hybridization of complementary oligonucleotides. A particularly simple and robust DNA device reported by Li and Tan is comprised of a single-strand 17-base oligomer that folds into a chairlike quadruplex structure. We have identified the key rate-limiting barrier in this device as the tendency for one of the fuel strands B to fold into the quadruplex configuration of the device strand. This seriously impedes the restoration reaction. We have designed a catalytic strand to inhibit the folding of B and shown that the catalyst speeds up the restoration reaction by roughly a factor of 2. The catalyst remains effective even after repeated cycling

Base Sequence↗

PubMed2004

Synergetic inhibition of metal ions and genistein on alpha-glucosidase.

Inhibition of metal ions and synergetic inhibition of metal ions/genistein on alpha-glucosidase activity has been investigated. We have examined the inhibitory effect of Cu2+, Ni2+, Mg2+, Fe2+, Hg2+, Zn2+, Ca2+, Pb2+, Ag+, V5+, V4+ and Mn2+ ions. The results show that the nature of the inhibition was reversible, slow-binding, non-competitive, and the Ki values of some ions such as Cu2+, Ni2+ and Zn2+ range from 10(-5) to 10(-6) M. Moreover, synergetic inhibitory effect of metal ions and genistein on alpha-glucosidase were studied with kinetics method. It is concluded that the inhibitory effect was much greater when both of them were added to the reactant solution simultaneously than that they were added, respectively, which suggests that the inhibitors seem to bind to the different sites of alpha-glucosidase at the same time. Furthermore, the mechanism of the synergetic inhibition was examined by spectrophotometry.

Calcium↗

PubMed2004

Synergetic inhibition of genistein and D-glucose on alpha-glucosidase.

Synergetic inhibitory effect of genistein (I2) and D-glucose (I1) on alpha-glucosidase has been studied with kinetics method. It was concluded that the inhibitory effect was much greater when I2 and I1 were both added to the reactant solution simultaneously than that they were added, respectively, which suggesting the inhibitors bind to the different sites of alpha-glucosidase at the same time, and demonstrating synergetic inhibition.

Drug Synergism↗

PubMed2004

Multiple anticancer effects of blocking MEK-ERK signaling in hepatocellular carcinoma.

BACKGROUND: Human hepatocellular carcinoma (HCC) is associated with increased expression and activity of mitogen-activated protein kinase (MAPK) signaling intermediates (ie, MEK, ERK). STUDY DESIGN: We determined the effects of MEK-ERK signaling on proliferation, cell cycle, apoptosis, and tumorigenicity of HCC in vitro. HCC cell lines were treated with MEK enzyme-specific inhibitors, PD098059 and U0126, and ERK1,2 oligonucleotide antisense. RESULTS: In the HCC cells examined, MEK inhibitors blocked ERK1,2 phosphorylation without a change in total ERK expression. ERK1,2 oligonucleotide antisense inhibited ERK1,2 protein expression. PD098059, U0126, and ERK1,2 oligonucleotide antisense each inhibited HCC cellular proliferation in a concentration-dependent manner. Cell cycle, apoptosis, and tumorigenicity were examined in Hep3B and HepG2 cell lines. MEK enzyme inhibition resulted in anticancer effects through cell cycle arrest, increased apoptosis, and decreased tumorigenicity in these cell lines. U0126 exhibited more potent inhibition of ERK1,2 phosphorylation and had more pronounced anticancer effects in both cell lines. Correspondingly, HepG2 cells, the cell line more sensitive to ERK1,2 phosphorylation inhibition, sustained more pronounced anticancer effects with treatment. But Hep3B cells were more sensitive to ERK1,2 antisense-mediated decreases in ERK1,2 protein expression and correspondingly, their growth was inhibited to a greater degree than the HepG2 cells. MEK enzyme inhibition had downstream effects on the expression of the antiapoptotic protein survivin in both cell lines. CONCLUSIONS: These data suggest that there are multiple anticancer effects of blocking MEK-ERK signaling, and that these depend on both the susceptibility of the cells and the ability of the treatment to effect a selective block of MEK-ERK signaling in HCC cells.

Apoptosis↗

PubMed2004

[Cloning and expression of immunoadjuvant molecule--CTB gene].

We cloned cholera toxin subunit B gene from 569B and M045 strain of Vibrio cholerae with polymerase chain reaction, constructed recombinant plasmid pCTB, and transformed pCTB into the prokaryotic cell strain JM109. The indentification was made by means of restriction enzyme analysis, polymerase chain reaction, DNA sequencing, SDS-polyacrylamine gel electrophoresis analysis and Western blot. The results indicate that we have amplified cholera toxin subunit B gene of 376 bp from Vibrio cholerae and hve constructed the recombinant plasmid pCTB, and we have affained the object amied at successful expression of 12 KD in the prokaryotic cell strain.

Adjuvants, Immunologic↗

PubMed2004

[Homocysteine-induced apoptosis of endothelial cell and its antagonism by folic acid--the roles of caspase3, c-IAP1 and c-IAP2].

OBJECTIVE: The present study addresses the question how Hcy induces endothelial apoptosis and how folic acid antagonizes the proapoptotic effects of Hcy. METHODS: Human umbilical vein endothelial cells (HUVEC) were treated with Hcy, with or without folic acid, for 24 hours. Cell apoptosis was evaluated by Annexin V staining and flow cytometery, as well as agarose gel analysis for genomic DNA ladder. The mRNA and protein levels of caspase3, c-IAP1, and c-IAP2 were analyzed by RT-PCR and Western blot, respectively. RESULTS: Treatment with both low (0.3 mmol/L) and high (3.0 mmol/L) concentrations of Hcy induced HUVEC apoptosis, with higher apoptotic rate at the latter case. Hcy-induced HUVEC apoptosis was accompanied by an increased level of caspase3 expression and activation, together with decreased c-IAP2 level. Folic acid upregulated c-IAP2 expression while attenuating Hcy-induced apoptosis and caspase3 activation. CONCLUSION: Hcy may induce HUVEC apoptosis via a pathway involving caspase3, which can be partially antagonized by folic acid, possibly through upregulated c-IAP2 expression.

Apoptosis↗

PubMed2003

Novel combination of cyclooxygenase-2 and MEK inhibitors in human hepatocellular carcinoma provides a synergistic increase in apoptosis.

Cyclooxygenase-2 (COX-2) and ERK-MAPK mitogenic signaling pathways are important in human hepatocellular carcinoma. We investigated the effect of COX-2 inhibition on ERK-MAPK signaling and the effect of combining MEK (MAPK kinase) and COX-2 inhibitors in human hepatocellular carcinoma in vitro. COX and ERK expression were determined by immunoblot in HepG2 and Hep3B cells. COX-2 and MEK activity were determined by prostaglandin E(2) assay and phosphospecific immunoblot, respectively. Cell growth was determined by cell proliferation and cell counts. Apoptosis was determined by DNA fragmentation enzyme-linked immunosorbent assay and flow cytometry. Cell cycle was determined by flow cytometry. HepG2 and Hep3B cells do not express COX-1 or COX-2. Correspondingly, basal and agonist (arachidonic acid, lipopolysaccharide)-stimulated COX-2 activity is undetectable. Treatment of HepG2 and Hep3B cells with NS398 resulted in an increase in ERK1/2 phosphorylation (MEK activity) in a concentration-dependent fashion (NS398, 1 to 100 micromol/L). Treatment with the COX-2 inhibitor NS398 in the presence of U0126 (MEK inhibitor) effectively suppressed ERK1/2 phosphorylation as determined by phosphospecific ERK1/2 immunoblot. Total ERK1/2 and COX-2 were unchanged with NS398 and U0126 treatments. In HepG2 cells, NS398 (1 to 100 micromol/L) decreased apoptosis as determined by DNA fragmentation enzyme-linked immunosorbent assay. Relative apoptosis was increased with U0126 alone or in combination with NS398 (9 to 10 times the control value), eliminating the anti-apoptotic effect of NS398. In Hep3B cells, apoptosis was unchanged with NS398 (1 to 50 micromol/L) or U0126 (1 to 10 micromol/L) alone. The combination of NS398 and U0126 in Hep3B cells resulted in a synergistic increase in apoptosis (10 times the control value). Relative apoptosis in both cell lines strongly correlated with changes in the expression of the antiapoptotic protein Bcl-xL. Cellular growth was assessed by colorimetric proliferation assay and cell counts. HepG2 and Hep3B cells had concentration-dependent inhibition of cell growth with NS398 or U0126 treatment alone. The combination of NS398 and U0126 resulted in complementary inhibitory effects on growth. Growth inhibitory effects in HepG2 and Hep3B cells with combination treatment appear to be, in part, secondary to the induction of G(0)/G(1) and G(2)/M cell cycle arrest, respectively, as determined by flow cytometry. Despite differential signaling in HepG2 and Hep3B cells, the sum effect of combining the COX-2 inhibitor NS398 and the MEK inhibitor U0126 results in enhanced antitumor actions. This novel combination may be useful for in vivo studies of hepatocellular carcinoma.

Adenocarcinoma↗

PubMed2002

Functional analysis of cone-rod homeobox (CRX) mutations associated with retinal dystrophy.

Mutations in the photoreceptor transcription factor cone-rod homeobox (CRX) have been identified in patients with several forms of retinal degenerative disease. To investigate the mechanisms by which these mutations cause photoreceptor degeneration, CRX constructs representing eleven known mutations, as well as a set of C-terminal deletions, were generated and tested for their ability to activate a rhodopsin-luciferase reporter in a transient cell transfection assay. To further define functional domains, several Gal4dbd-Crx fusions were similarly tested using a Gal4 response element containing heterologous promoter. This analysis demonstrated that the C-terminal region, between amino acids 200 and 284, is essential for CRX-mediated transcriptional activation. Consistent with this, four mutants carrying C-terminal truncations demonstrated significantly reduced transcriptional activation. Confirming the importance of the homeodomain (HD), four of the five mutants carrying HD missense mutations displayed altered transactivating activity, either decreased (three) or increased (one). In vitro protein-DNA binding assays (EMSAs) with CRX-HD peptides representing the three HD mutants with decreased transactivating activity, indicated that the alteration was due to reduced, but not abolished, DNA binding to CRX targets. Taken together, these results support the hypothesis that CRX mutations involved in human photoreceptor degeneration act by impairing CRX-mediated transcriptional regulation of the photoreceptor genes. However, a clear relationship between the magnitude of biochemical abnormality and degree of disease severity was not observed, suggesting that other genetic and environmental modifiers may also contribute to the disease phenotype.

Amino Acid Sequence↗

PubMed2002

The effect of catalyst concentration on the synthesis of single-wall carbon nanotubes.

Single wall carbon nanotubes (SWNTs) were synthesized by electric arc discharge method with a mixture of nickel and yttrium as catalysts. The effect of the catalyst concentration on the synthesis of SWNTs was studied. Raman spectra of SWNTs have been recorded with excitation wavelengths from 476.5 to 1064 nm. The Raman peaks of the radial breathing modes (RBM) of SWNTs were assigned. The results indicate that the diameter distribution of SWNTs is in the range of 1.2-1.6 nm, and the SWNTs with diameter 1.43 nm are in the majority. The catalyst concentrations have large effect on the yield of SWNTs and little effect on the diameter distribution of SWNTs.

Carbon Compounds, Inorganic↗