Biomedical subjects

Seok-Il Hong

Publications and source records attributed to Seok-Il Hong.

26 records · Page 2Linked to original sources

PubMed2003

Procaspase-3 and its active large subunit localized in both cytoplasm and nucleus are activated following application of apoptotic stimulus in Ramos-Burkitt lymphoma B cells.

Ramos-Burkitt lymphoma (Ramos-BL) B cell line is a neoplastic model of normal B cell selection by apoptosis at the germinal center site during maturation of the humoral immune response and can be triggered into apoptosis by cross-linking their surface antigen receptor with antibodies directed against immunoglobulin (Ig)M (anti-IgM) or by treating with the calcium ionophore ionomycin. We have recently demonstrated that anti-IgM and ionomycin trigger significant activation of caspase-3, -7 and -8 and for cleavage of the resident nuclear proteins poly(ADP-ribose) polymerase (PARP) and lamin B1 in Ramos-BL B cells, suggesting that these caspases may be localized to the nucleus as well as to the cytoplasm of Ramos-BL B cells. In order to examine this hypothesis further, we fractionated Ramos-BL B cells into their cytosolic and nuclear components and examined for expression of the endogenous proform and active large subunit of caspase-3; procaspase-3 and its active p17 large subunit were identified in both the cytosolic and nuclear fractions of Ramos-BL B cells. Immunofluorescence staining together with ordinary and confocal microscopy confirmed the observations that procaspase-3 immunoreactivity was clearly identified in the cytoplasm and nucleus while Fas ligand staining was localized to the cell surface and PARP immunoactivity to the nucleus, which were used as controls; procaspase-3 exhibited granular nuclear immunoreactivity whereas PARP displayed diffuse nuclear immunoreactivity; both of which was more intense in the internucleolar regions. Taken together, we now present evidence that procaspases and their active large subunits are found in both the cytoplasm and the nucleus and that procaspases localized not only in the cytoplasm but also in the nucleus are activated following application of apoptotic stimulus in Ramos-BL B cells.

Antibodies, Anti-Idiotypic↗

PubMed2003

Tetraarsenic oxide induces apoptosis in U937 leukemic cells through a reactive oxygen species-dependent pathway.

In the present study, we investigated the effect of tetraarsenic oxide (As4O6, 2,4,6,8,9,10-Hexaoxa-1,3,5,7-tetraarsatricyclo[3.3.1.13,7]decane) upon induction of apoptosis in arsenic trioxide (diarsenic oxide, As2O3) resistant U937 leukemic cells. As4O6 induced apoptosis in U937 leukemic cells at much lower concentrations than As2O3 via an early increase of cellular reactive oxygen species (ROS), and a decrease in cellular mitochondrial membrane potential, followed by cytochrome c release and caspase-3 activation. As4O6 generated ROS and induced caspase-3 activation more potently than As2O3 in U937 cells. Incubation of the cells with N-acetyl-L-cysteine and catalase resulted in significant suppression of As4O6-induced apoptotic cell death. These results show that the generation of ROS leads to the consequences associated with apoptosis induced by As4O6. In conclusion, As4O6 might be a new arsenic compound which may induce apoptosis in U937 leukemic cells by activating unique apoptotic signaling mediated by ROS more potently than As2O3, and deserves further evaluation.

Apoptosis↗

PubMed2002

PTEN suppresses hyaluronic acid-induced matrix metalloproteinase-9 expression in U87MG glioblastoma cells through focal adhesion kinase dephosphorylation.

Glioblastoma is a severe type of primary brain tumor and its invasion is strongly correlated with the secretion of matrix metalloproteinases (MMPs). To investigate a role of PTEN, a tumor suppressor gene, in the regulation of hyaluronic acid (HA)-induced invasion of glioma cells, we examined the secretion of MMP-9 in various glioma cells with or without a functional PTEN gene. The secretion of MMP-9 in glioma cells lacking functional PTEN (U87MG, U251MG, and U373MG) was induced by HA, although not in wildtype (wt)-PTEN-harboring cells (LN229, LN18, and LN428). In addition, stable expression of wt-PTEN into U87MG cells significantly decreased the secretion of HA-induced MMP-9 and basal levels of MMP-2, inhibiting the activation of focal adhesion kinase and extracellular signal-regulated kinase 1/2, whereas the secretion levels of the tissue inhibitor of metalloproteinase-1 and -2 were increased, finally resulting in the inhibition of invasion by HA in vitro. Ectopic expressions of adenoviral (Ad)-wt-PTEN and -lipid phosphatase-deficient (G129E)-PTEN, but not both protein and -lipid phosphatase-deficient (C124S)-PTEN, reduced MMP-9 secretion and invasion by HA. These results were also confirmed by expressions of Ad-wt-PTEN and Ad-G129E-PTEN in other glioblastoma cells lacking functional PTEN, U251MG, and U373MG. These findings strongly suggest the possibility that PTEN may block HA-induced MMP-9 secretion and invasion through its protein phosphatase activity.

Focal Adhesion Kinase 1↗

PubMed2002

Modulation of phorbol ester-induced regulation of matrix metalloproteinases and tissue inhibitors of metalloproteinases by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase.

OBJECT: Expression of matrix metalloproteinases (MMPs) has been postulated to play a central role in brain tumor invasion; however, its underlying mechanism is not yet fully understood. In the present study, by assessing the effect of a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, on the secretion of MMPs and in vitro invasion of various glioma cells, the authors attempt to define the role of the p38 MAPK pathway in the regulation of MMPs and tissue inhibitors of metalloproteinases (TIMPs) activated by phorbol ester (phorbol-12-myristate-13-acetate [PMA]) in the D54 human glioblastoma cell line. METHODS: The activation of MAPKs was determined using Western blot analysis after addition of phospho-specific antibodies against these kinases, the status of MMPs and TIMPs was analyzed using gelatin zymography and Western blot analysis, and the invasion rate of D54 cells and other glioma cells was analyzed using a modified Boyden chamber assay. Treatment of D54 cells with PMA activated two distinct MAPKs, extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK, but not c-Jun N-terminal kinase/stress-activated protein kinase. Induction of MMP-9 production and MMP-2 activation by PMA were blocked by SB203580, a specific inhibitor of p38 MAPK, but not by PD98059, a specific inhibitor of ERK 1/2. In addition, PMA-induced downregulation of TIMP-1 and TIMP-2 secretion and upregulation of the membrane type I MMP, a major activator of MMP-2 on the cell surface, were reversed by SB203580 in these cells; the PMA-induced increase of invasion in vitro decreased when SB203580 was added to the top compartment of a modified Boyden chamber; and the inhibitor also reduced the MMP secretion and PMA-induced in vitro invasion in various glioma cell lines. CONCLUSIONS: These results indicate that activation of p38 MAPK by PMA plays a central role in the regulation of MMPs and TIMPs in D54 cells, which has a major influence in tumor invasion and metastasis. Furthermore, inhibition of p38 MAPK by SB203580 blocked the secretion of MMPs and in vitro invasion of various glioma cells, underscoring a possible role of p38 MAPK inhibitors as antiinvasive and/or antimetastatic agents of malignant gliomas.

Biocompatible Materials↗

PubMed2002

Arsenic trioxide induces apoptosis through a reactive oxygen species-dependent pathway and loss of mitochondrial membrane potential in HeLa cells.

Arsenic trioxide (As2O3) can induce clinical remission in patients with acute promyelocytic leukemia (APL) through induction of apoptosis. To investigate the potential therapeutic usage of As2O3 in cervical cancer and its possible mechanisms, human cervical cancer cell line HeLa was employed. The cells underwent apoptosis in response to As2O3, accompanied by a decrease of mitochondrial membrane potential and caspase-3 activation. Overexpression of Bcl-2, however, prevented the dissipation of mitochondrial membrane potential, subsequently protecting the cells from As2O3-induced apoptosis. As2O3 increased cellular content of reactive oxygen species (ROS), especially hydrogen peroxide (H2O2), and the antioxidant N-acetyl-L-cysteine completely suppressed As2O3-induced apoptosis. Furthermore, incubation of the cells with catalase resulted in significant suppression of As2O3-induced apoptosis. The above results indicate that the induction of HeLa cell apoptosis by As2O3 involved an early decrease in cellular mitochondrial membrane potential and increase in ROS content, predominantly H2O2, followed by caspase-3 activation and DNA fragmentation.

Acetylcysteine↗

PubMed2002

Curcumin inhibits cell cycle progression of immortalized human umbilical vein endothelial (ECV304) cells by up-regulating cyclin-dependent kinase inhibitor, p21WAF1/CIP1, p27KIP1 and p53.

To elucidate possible mechanisms of anti-angiogenic activity by curcumin, we performed cDNA microarray and found that curcumin modulated cell cycle related gene expression. For further confirmation, DNA contents and expression levels of cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors (CDKIs) were examined by FACS analysis and Western blotting, respectively. Curcumin was found to induce G0/G1 and/or G2/M phase cell cycle arrest, up-regulate CDKIs, p21WAF1/CIP1, p27KIP1, and p53, and slightly down-regulate cyclin B1 and cdc2 in ECV304 cells. However, expression level of other cyclins and CDKs were not changed by curcumin. We, therefore, conclude that the up-regulation of CDKIs by curcumin plays a critical role in the regulation of cell cycle distribution in these cells, which may have a major role in anti-angiogenic activity of curcumin.

Antineoplastic Agents↗

PubMedDate not supplied

Heterogeneity of capillary endothelial cells for basic fibroblast growth factor-induced paracrine signaling.

In this study, the authors isolated morphologically different capillary endothelial cells, designated as BCE-1 and BCE-2 cells, from bovine adrenal cortex. By a series of experiments involving proliferation, migration, and tubular-like structure formation assays, the authors found that the two BCE clones showed a clearly different response to basic fibroblast growth factor (bFGF). Similar to these results, the ERK-1/2 in the BCE-1 cells was phosphorylated by bFGF or vascular endothelial growth factor (VEGF), whereas that of the BCE-2 cells was phosphorylated only by VEGF. However, when the BCE-2 cells were transfected with FGF receptor 1 cDNA, the ERK-1/2 of these cells was phosphorylated by exogenous bFGF. Receptor binding experiments revealed that BCE-2 cells expressed high-affinity tyrosine-kinase FGF receptors approximately twofold less than BCE-1 cells. Transfection and receptor binding studies suggest a possibility that the poor response of the BCE-2 cells to exogenous bFGF is derived from the limitation of functional availability of high affinity FGF receptors. On the other hand, when both BCE clones were treated with anti-bFGF antibodies, basal formation of tubular-like structure in both clones were strongly inhibited, indicating that endogenous bFGF plays a role in in vitro angiogenesis of both BCE clones. Taken together, these data show that the isolated capillary endothelial cells are heterogeneous for paracrine but not autocrine bFGF signaling, and suggest that the diversity of capillary endothelial cells can occur by angiogenic factors, such as bFGF.

Adrenal Cortex↗

PubMedDate not supplied

Ionizing radiation and nitric oxide donor sensitize Fas-induced apoptosis via up-regulation of Fas in human cervical cancer cells.

Fas/CD95/Apo1 is a transmembrane receptor known to trigger apoptotic cell death in several cell types. In the present study, we showed that ionizing radiation (IR) and NO donor, S-nitroso-N-acetyl-penicillamine (SNAP), sensitized Fas-induced apoptotic cell death of HeLa human cervical cancers. Suboptimal dose of IR and SNAP up-regulated the cell-surface Fas antigen, detected by FACScan using FITC-anti-Fas antibody. When combined with IR or SNAP, agonistic anti-Fas antibody CH-11 resulted in marked enhancement of apoptosis. This sensitization was completely abrogated by anti-Fas neutralizing antibody ZB4. During the IR and SNAP sensitized Fas-induced apoptosis, mitochondria permeabilization, cytochrome c release, and DNA fragmentation were detected. Furthermore, combined treatment of IR and SNAP additively up-regulated the surface Fas protein expression and sensitized Fas-induced apoptosis. Our findings demonstrate that sensitization of HeLa cervical cells to Fas-mediated apoptosis by IR and NO donor is most likely due to the up-regulation of Fas expression and also provides a means with which to sensitize tumors to the killing effects of cancer therapy via the Fas receptor.

Annexin A5↗