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Biomedical subjects

W T Chen

Publications and source records attributed to W T Chen.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Apoptosis of Tca8113 cells induced by cisplatin and their cell cycle specificity].

OBJECTIVE: Evaluating the effect of apoptosis induced by cisplatin in human oral squamous cell carcinoma cells and their cycle specificity. METHODS: Hu man tongue squamous cell carcinoma cell line Tca8113 was used in vitro as a study object. Morphological features of apoptotic cell induced by cisplatin were observed by using of microscope, fluorescence microscope and transmission electronic microscope (TEM). The apoptotic rates were analyzed by DNA fluorescence staining assay and TEM observation. The cell cycle specificity was measured by using flow cytometry. RESULTS: The cell proliferation of Tca8113 cells was inhibited by cisplatin and their proliferation index decreased. Cells treated with cisplatin became smaller, rounded and then disattached. Red nuclear fragmentation with condensed chromatin was observed under fluorescence staining assay. Condensation and crack of nucleus and apoptotic bodies appeared in apoptotic Tca8113 cells observed under TEM. Cell cycle of Tca8113 cells was apparently arrested at S by cisplatin. CONCLUSION: Apoptosis was induced by cisplatin in Tca8113 cells, and it may be an important mechanism of SCC killed by cisplatin.

English Abstract↗
PubMed2000

[Experimental study of abnormal cell proliferation and differentiation in rat tongue carcinogenesis induced by 4NQO].

OBJECTIVE: To clarify the phenotypic characteristics of abnormal cell proliferation and differentiation in oral carcinogenesis. METHODS: The expressions of gp230, a marker of epithelium cell differentiation, and proliferating cell nuclear antigen (PCNA) in rat tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO) were detected by LSAB immunohistochemical staining. RESULTS: With the progress of oral carcinogenesis abnormal proliferation and differentiation patterns were indicated by reduced expression of gp230 and increased expression of PCNA. CONCLUSION: Oral carcinogenesis is the result of mucosa epithelium cell aberrant proliferation and differentiation.

English Abstract↗
PubMed1999

A novel protease-docking function of integrin at invadopodia.

Invadopodia are membrane extensions of aggressive tumor cells that function in the activation of membrane-bound proteases occurring during tumor cell invasion. We explore a novel and provocative activity of integrins in docking proteases to sites of invasion, termed invadopodia. In the absence of collagen, alpha(3)beta(1) integrin and the gelatinolytic enzyme, seprase, exist as nonassociating membrane proteins. Type I collagen substratum induces the association of alpha(3)beta(1) integrin with seprase as a complex on invadopodia. The results show that alpha(3)beta(1) integrin is a docking protein for seprase to form functional invadopodia. In addition, alpha(5)beta(1) integrin may participate in the adhesion process necessary for invadopodial formation. Thus, alpha(3)beta(1) and alpha(5)beta(1) integrins play major organizational roles in the adhesion and formation of invadopodia, promoting invasive cell behavior.

Animals↗
PubMed1999

Specialized surface protrusions of invasive cells, invadopodia and lamellipodia, have differential MT1-MMP, MMP-2, and TIMP-2 localization.

Surface protrusions, invadopodia, and analogous lamellipodia at the leading edge of an invasive cell, which make contact with the underlying extracellular matrix (ECM), are the main motor for cellular locomotion and invasion. Previous studies have demonstrated that invadopodia, but not lamellipodia, are sites of ECM degradation on the cell surface. Such degradative activity is in part due to the localization of latent matrix metalloproteinase-2 (MMP-2) and membrane type-1 MMP (MT1-MMP) to invadopodia, where MMP activation occurs. Although lamellipodia exhibit similar structure and mobility to invadopodia, lamellipodia, by virtue of their location at the cellular periphery, are readily accessible to the soluble tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and blood-borne inhibitors. We show here that TIMP-2 co-localizes with MT1-MMP and MMP-2 at lamellipodia but not with that of invadopodia. Thus, the MMP-TIMP localization at lamellipodia may be a key mechanism for the regulation of MMP activation on the cell surface, which in turn governs expression of the cell-invasive phenotype.

Amino Acid Sequence↗
PubMed1999

Effects of all-trans retinoic acid and interferon-gamma on expression of RAR beta gene in Tca8113 cells.

OBJECTIVE: All-trans-retinoic acid (ATRA) and interferons (IFNs) have been proven to synergistically amplify growth inhibition and apoptosis in the tongue squamous carcinoma cell line (Tca8113). Nuclear retinoic acid receptor-beta (RAR beta) was the key gene that mediated retinoid activity for squamous carcinoma cells. In order to understand the mechanism of ATRA combined with IFN gamma inhibiting growth of Tca8113 cells, this investigation focused on RAR beta mRNA expression. MATERIALS AND METHODS: In this experiment, RT-PCR method was used to analyze the RAR beta expression level, and viable cell count assay was carried out for growth inhibition studies. RESULTS: All-trans-retinoic acid (1 microM) and IFN gamma (1000 u/mL) inhibited cell growth by 39.2% and 44.4%, respectively. Synergistic inhibition of cell proliferation by 86.7% was found under combined treatment. The combination of suboptimal concentrations of ATRA (0.1 microM) with IFN gamma (1000 u/mL) showed a much stronger additive inhibitory effect on cell proliferation. ATRA (1 microM) and IFN gamma (1000 u/mL) increased RAR beta expression to 4 times and 3 times, respectively. The expression of RAR beta increased 12 times after treatment with combined ATRA and IFN gamma treatment. CONCLUSIONS: These observations indicated that the use of combined ATRA and IFN may lead to enhanced antitumor effects. These results also suggested that ATRA and IFN mediated upregulating expression of RAR beta may play an important role in synergistic inhibition of proliferation in Tca8113 cells.

Carcinoma, Squamous Cell↗
PubMed1999

[Studies of radiosensitizative effect of BSO on Acc-2 cells]

OBJECTIVE:To study the radiosensitizative effect of buthione sulfoximin (BSO) on Acc-2 cells.METHODS:First,the pharmotoxicity of BSO to Acc-2 cells under hypoxic or aerobic conditions was measured.Second,the radiosensitizative effect of BSO on Acc-2 cells under hypoxic or aerobic conditions was studied.Plating efficiency assay was used in this experiment.RESUTS:The 50% inhibition dose (ID50) of BSO to Acc-2 cells under hypoxic or aerobic condition was 80 micromol/L,120micromol/L,respectively.When the dose of BSO was ID20 and ID10 under hypoxic or aerobic condition the SER was 1.521,1.263 and 1.296,1.153,respectively.CONCLUSION:BSO had radiosensitizative effect on Acc-2 cells both under hypoxic or aerobic condition.The radiosensitizative effect of BSO on Acc-2 cells under hypoxic condition was stronger than that under aerobic condition.

Journal Article↗
PubMed1999

[Experimental study of radiosensitization of buthionine sulffoximine (BSO) on Acc-2 transplanted tumor]

OBJECTIVE:The effect of radiosensitization of BSO on Acc-2 transplanted tumor was studied in vivo.METHODS: There were four groups in this experiment:control group,radiation group and BSO+radiation group.The drug dose of BSO is 5mmol/kg and the radiation dose was 10Gy. RESULTS:The result demonstrated that the tumor inhibitive rate was 8.5%,12.6% and 45.37% respectively compared with control group. CONCLUSION: BSO has radiosensitizative effect on Acc-2 transplanted tumor.

Journal Article↗
PubMed1998

Neuropeptide Y: a novel angiogenic factor from the sympathetic nerves and endothelium.

Sympathetic nerves have long been suspected of trophic activity, but the nature of their angiogenic factor has not been determined. Neuropeptide Y (NPY), a sympathetic cotransmitter, is the most abundant peptide in the heart and the brain. It is released during nerve activation and ischemia and causes vasoconstriction and smooth muscle cell proliferation. Here we report the first evidence that NPY is angiogenic. At low physiological concentrations, in vitro, it promotes vessel sprouting and adhesion, migration, proliferation, and capillary tube formation by human endothelial cells. In vivo, in a murine angiogenic assay, NPY is angiogenic and is as potent as a basic fibroblast growth factor. The NPY action is specific and is mediated by Y1 and Y2 receptors. The expression of both receptors is upregulated during cell growth; however, Y2 appears to be the main NPY angiogenic receptor. Its upregulation parallels the NPY-induced capillary tube formation on reconstituted basement membrane (Matrigel); the Y2 agonist mimics the tube-forming activity of NPY, whereas the Y2 antagonist blocks it. Endothelium contains not only NPY receptors but also peptide itself, its mRNA, and the "NPY-converting enzyme" dipeptidyl peptidase IV (both protein and mRNA), which terminates the Y1 activity of NPY and cleaves the Tyr1-Pro2 from NPY to form an angiogenic Y2 agonist, NPY3-36. Endothelium is thus not only the site of action of NPY but also the origin of the autocrine NPY system, which, together with the sympathetic nerves, may be important in angiogenesis during tissue development and repair.

Animals↗
PubMed1998

Activation of beta1 integrin signaling stimulates tyrosine phosphorylation of p190RhoGAP and membrane-protrusive activities at invadopodia.

The ligation of available alpha6beta1 integrin in adherent LOX melanoma cells by laminin G peptides and integrin stimulatory antibodies induced cell invasiveness, independent of adhesion activity of integrins that were pre-bound to extracellular matrix (Nakahara, H., Nomizu, M., Akiyama, S. K., Yamada, Y., Yeh, Y., and Chen, W.-T. (1996) J. Biol. Chem. 271, 27221-27224). Here, we show that this induced invasion involves an increase in tyrosine phosphorylation of a 190-kDa GTPase-activating protein for Rho family members (p190(RhoGAP); p190) and membrane-protrusive activities at invadopodia. This tyrosine phosphorylation does not occur when the adherent cells are treated with non-activating antibody against beta1 integrin, control laminin peptides, or tyrosine kinase inhibitors genistein and herbimycin A. Although p190 and F-actin co-distribute in all cell cortex extensions, tyrosine-phosphorylated proteins including p190 appear to associate with F-actin specifically in invadopodia. In addition, the localized matrix degradation and membrane-protrusive activities were blocked by treatment of LOX cells with tyrosine kinase inhibitors as well as microinjection of antibodies directed against p190 but not by non-perturbing antibodies or control buffers. We suggest that activation of the alpha6beta1 integrin signaling regulates the tyrosine phosphorylation state of p190 which in turn connects downstream signaling pathways through Rho family GTPases to actin cytoskeleton in invadopodia, thus promoting membrane-protrusive and degradative activities necessary for cell invasion.

Amino Acid Sequence↗
PubMed1998

Carbon dioxide enhanced ultrasonography of hepatic haemangiomas.

The purpose of this study was to characterize the imaging manifestations of carbon dioxide enhanced ultrasonography (CO2US) in hepatic haemangiomas. CO2US was performed for 52 haemangiomas in 25 patients and for 352 various hepatic nodules in 192 patients. Characteristic enhancement patterns for hepatic haemangiomas were noted. All 39 large haemangiomas (> 1 cm) demonstrated peripheral nodular enhancement in the early and parenchymal phases associated with delayed washout character (> 30 min). Centripetal fill-in of CO2 was noted in 82.1% of large haemangiomas. Two enhancing patterns were noted in 13 small haemangiomas (< 1 cm): peripheral nodular (69.2%) and homogeneous (30.8%). Delayed washout was also noted in all small haemangiomas. Centripetal fill-in of CO2 was hard to define in small haemangiomas. None of the other 352 hepatic nodules had the same imaging features. In conclusion we found that CO2US is valuable in differentiating hepatic haemangiomas from other liver tumours in clinically doubtful cases.

Adult↗
PubMed1998

Intra-arterial carbon dioxide-enhanced ultrasonogram of hepatocellular carcinoma treated by transcatheter arterial embolization and percutaneous ethanol injection therapy.

The purpose of this study was to investigate the value of carbon dioxide-enhanced ultrasonography (CO2-US) in the evaluation of viable hepatocellular carcinomas (HCC) which were treated by transcatheter arterial embolization (TAE), percutaneous ethanol injection (PEI), or a combination treatment (TAE and PEI). Forty-one patients with 66 HCC were included in the study. They underwent CO2-US and angiography were performed in all tumours after they were treated by TAE, PEI or a combination treatment. Forty-six tumours were positively enhanced by CO2-US and 40 of them were positive by angiography. These 46 tumours were proved to be viable tumours either by biopsy or by follow-up studies. The positive predictive value was 100% for CO2-US and 87.8% in angiography. Twenty tumours were negative by CO2-US and these were also negative by angiography. Carbon dioxide-enhanced ultrasonography is a more reliable method for detecting the viable portion of the treated HCC compared with conventional angiography.

Adult↗
PubMed1997

Transmembrane/cytoplasmic domain-mediated membrane type 1-matrix metalloprotease docking to invadopodia is required for cell invasion.

The invasion of human malignant melanoma cells into the extracellular matrix (ECM) involves the accumulation of proteases at sites of ECM degradation where activation of matrix metalloproteases (MMP) occurs. Here, we show that when membrane type 1 MMP (MT-MMP) was overexpressed in RPMI7951 human melanoma cells, the cells made contact with the ECM, activated soluble and ECM-bound MMP-2, and degraded and invaded the ECM. Further experiments demonstrated the importance of localization of the MT-MMP to invadopodia. Overexpression of MT-MMP without invadopodial localization caused activation of soluble MMP-2, but did not facilitate ECM degradation or cell invasiveness. Up-regulation of endogenous MT-MMP with concanavalin A caused activation of MMP-2. However, concanavalin A treatment prevented invadopodial localization of MT-MMP and ECM degradation. Neither a truncated MT-MMP mutant lacking transmembrane (TM) and cytoplasmic domains (DeltaTMMT-MMP), nor a chimeric MT-MMP containing the interleukin 2 receptor alpha chain (IL-2R) TM and cytoplasmic domains (DeltaTMMT-MMP/TMIL-2R) were localized to invadopodia or exhibited ECM degradation. Furthermore, a chimera of the TM/cytoplasmic domain of MT-MMP (TMMT-MMP) with tissue inhibitor of MMP 1 (TIMP-1/TMMT-MMP) directed the TIMP-1 molecule to invadopodia. Thus, the MT-MMP TM/cytoplasmic domain mediates the spatial organization of MT-MMP into invadopodia and subsequent degradation of the ECM.

Amino Acid Sequence↗
PubMed1997

Molecular cloning of seprase: a serine integral membrane protease from human melanoma.

Seprase is a homodimeric 170 kDa integral membrane gelatinase whose expression correlates with the invasiveness of the human melanoma cell line LOX. Here, we report the molecular cloning of a cDNA that encodes the 97 kDa subunit of seprase. Its deduced amino acid sequence predicts a type II integral membrane protein with a cytoplasmic tail of 6 amino acids, followed by a transmembrane domain of 20 amino acids and an extracellular domain of 734 amino acids. The carboxyl terminus contains a putative catalytic region (approximately 200 amino acids) which is homologous (68% identity) to that of the nonclassical serine protease dipeptidyl peptidase IV (DPPIV). The conserved serine protease motif G-X-S-X-G is present as G-W-S-Y-G. However, sequence analysis of seprase cDNA from LOX and other cell lines strongly suggests that seprase and human fibroblast activation protein alpha (FAP alpha) are products of the same gene. We propose that seprase/FAP alpha and DPPIV represent a new subfamily of serine integral membrane proteases (SIMP).

Amino Acid Sequence↗
PubMed1997

Identification of the 170-kDa melanoma membrane-bound gelatinase (seprase) as a serine integral membrane protease.

The 170-kDa membrane-bound gelatinase, seprase, is a cell surface protease, the expression of which correlates with the invasive phenotype of human melanoma and carcinoma cells. We have isolated seprase from cell membranes and shed vesicles of LOX human melanoma cells. The active enzyme is a dimer of N-glycosylated 97-kDa subunits. Sequence analysis of three internal proteolytic fragments of the 97-kDa polypeptide revealed up to 87.5% identity to the 95-kDa fibroblast activation protein alpha (FAPalpha), the function of which is unknown. Thus, we used reverse transcription-polymerase chain reaction to generate a 2.4-kilobase cDNA from LOX mRNA with FAPalpha primers. COS-7 cells transfected with this cDNA expressed a 170-kDa gelatinase that is recognized by monoclonal antibodies directed against seprase. Sequence analysis also showed similarities to the 110-kDa subunit of dipeptidyl peptidase IV (DPPIV). Like DPPIV, the gelatinase activity of seprase was completely blocked by serine-protease inhibitors, including diisopropyl fluorophosphate. Seprase could be affinity-labeled by [3H]diisopropyl fluorophosphate, but the proteolytically inactive 97-kDa subunit could not, confirming the existence of a serine protease active site on the dimeric form. Proteolytic activity is lost upon dissociation into its 97-kDa subunit following treatment with acid, heat, or cysteine and histidine-modifying agents. We conclude that seprase, FAPalpha, and DPPIV are related serine integral membrane proteases and that seprase is similar to DPPIV, the proteolytic activities of which are dependent upon subunit association.

Amino Acid Sequence↗
PubMed1996

A mechanism for regulation of melanoma invasion. Ligation of alpha6beta1 integrin by laminin G peptides.

Invasion of LOX human melanoma cells involves extracellular matrix (ECM) degradation and formation of cell surface invadopodia. Here we show that the ligation of alpha6beta1 by two peptides derived from the COOH-terminal globular domain of laminin-1 alpha1 chain (laminin G peptides), designated AG-10 (NPWHSIYITRFG) and AG-32 (TWYKIAFQRNRK), and antibodies against alpha6 and beta1 integrins promoted invasiveness. AG-10 and AG-32 inhibited cell adhesion on laminin, and the antibodies blocked cell adhesion on immobilized AG-10 and AG-32, suggesting that the peptides interact primarily with alpha6beta1 integrin. These soluble peptides and integrin antibodies induced invasiveness by causing an 2-3-fold increase in ECM degradation and invadopodial activity independently of adhesion activity of integrins that were prebound to ECM. The induced ECM degradation and invasion was associated with an increased surface expression of the 170-kDa membrane-bound gelatinase, seprase, as well as its intense localization at invadopodia but not at focal adhesions. However, the total expression levels of seprase, gelatinase A and beta1 integrins were not altered. We suggest that laminin G peptides act on the alpha6beta1 integrin signaling of invasion by stimulating invadopodial activities, which is distinct from their direct effects on cell adhesion on immobilized ECM.

Amino Acid Sequence↗
PubMed1996

Blood pressure-lowering effect of fish oil is independent of thromboxane A2 level in spontaneously hypertensive rats.

Whether the alterations in the synthesis of thromboxane A2 (TXA2) is the direct mechanism underlying the blood pressure-lowering effect of fish oil was investigated in this study. Six groups of 11 male spontaneously hypertensive rats were fed semipurified diets containing corn or fish oils and graded levels (50, 5000 or 15,000 ppm) of dietary vitamin E for 8 weeks. Plasma TXA2, assayed by RIA, was significantly greater in the corn oil group than in the fish oil group (P < 0.05). Compared to 50 ppm dietary vitamin E, 5000 and 15 000 ppm dietary vitamin E, respectively, significantly decreased plasma TXA2 (P < 0.05). Systolic, mean or diastolic blood pressure, evaluated by the tail cuff method, were significantly higher in the corn oil group than in the fish oil group (P < 0.05). However, vitamin E had no effect on blood pressure. No relationship between TXA2 and blood pressure was found. Experimental results indicated that the alterations in the synthesis of TXA2 were not the direct antihypertensive effect of fish oil.

Animals↗
PubMed1996

Proteases associated with invadopodia, and their role in degradation of extracellular matrix.

Metastasizing cancer cells invade the extracellular matrix using plasma membrane protrusions (invadopodia) that contact and dissolve the matrix. Evidence suggests that membrane-associated proteases, 170-kD gelatinase (seprase) and Gelatinase A, exert their mechanisms of action on invadopodia. Potential roles that other metallo- and serine-types of membrane proteases, including membrane-type matrix metalloprotease, meprin, dipeptidyl peptidase IV, fibroblast activation protein alpha and guanidinobenzoatase, play in the cell surface proteolysis are also discussed. It is proposed that formation of a structurally and functionally linked protease complex on invadopodia allows the invasion of cancer cells into the extracellular matrix.

Animals↗