Biomedical subjects

Chan-Wook Woo

Publications and source records attributed to Chan-Wook Woo.

4 recordsLinked to original sources

PubMed2006

Predictive risk factors for coronary artery abnormalities in Kawasaki disease.

Clinical characteristics to predict the development of coronary artery abnormalities (CAA) in Kawasaki disease (KD) were assessed by reviewing medical records of patients diagnosed with KD at Korea University Medical Center from March 2001 to February 2005. Of the 285 patients diagnosed with KD, 19 developed CAA (6.7%). Compared with the CAA(-) group, the CAA(+) group had a longer duration of fever after intravenous gamma-globulin (IVGG) injection (2.4+/-2.9 vs. 1.5+/-1.2 days, p=0.008) and higher C-reactive protein (CRP)(12.3+/-7.8 vs. 8.7+/-7.1 mg/dL, p=0.038). In particular, the CAA(+) group tended to have more than 7 days of fever before IVGG and more than 3 days of fever after IVGG (26.3 vs. 5.3%, p<0.001; 26.3 vs. 6.4%, p=0.002). When the IVGG responsiveness was defined by the presence of defervescence within 3 days after IVGG, IVGG-non-responders showed a higher incidence of CAA (22.7 vs. 5.3%, p=0.002). Non-responders had a longer duration of fever after IVGG (5.5+/-1.9 vs. 1.2+/-0.6 days, p<0.001) and a significantly increased CRP, AST, ALT and total bilirubin. Multivariate regression analysis for CAA showed that the only factor significantly associated with the development of CAA was total fever that lasted for longer than 8 days (OR=4.052, 95% CI=1.151-14.263, p=0.0293). Conclusively, the most important predictor of CAA in KD is total duration of fever longer than 8 days. Early identification of IVGG non-responders and active therapeutic intervention for fever in KD cases might decrease the incidence of CAA.

Chi-Square Distribution↗

PubMed2006

Brain-derived neurotrophic factor activation of TrkB induces vascular endothelial growth factor expression via hypoxia-inducible factor-1alpha in neuroblastoma cells.

The extent of angiogenesis and/or vascular endothelial growth factor (VEGF) expression in neuroblastoma tumors correlates with metastases, N-myc amplification, and poor clinical outcome. Recently, we have shown that insulin-like growth factor-I and serum-derived growth factors stimulate VEGF expression in neuroblastoma cells via induction of hypoxia-inducible factor-1alpha (HIF-1alpha). Because another marker of poor prognosis in neuroblastoma tumors is high expression of brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor, TrkB, we sought to evaluate the involvement of BDNF and TrkB in the regulation of VEGF expression. VEGF mRNA levels in neuroblastoma cells cultured in serum-free media increased after 8 to 16 hours in BDNF. BDNF induced increases in VEGF and HIF-1alpha protein, whereas HIF-1beta levels were unaffected. BDNF induced a 2- to 4-fold increase in VEGF promoter activity, which could be abrogated if the hypoxia response element in the VEGF promoter was mutated. Transfection of HIF-1alpha small interfering RNA blocked BDNF-stimulated increases in VEGF promoter activity and VEGF protein expression. The BDNF-stimulated increases in HIF-1alpha and VEGF expression required TrkB tyrosine kinase activity and were completely blocked by inhibitors of phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) pathways. These data indicate that BDNF plays a role in regulating VEGF levels in neuroblastoma cells and that targeted therapies to BDNF/TrkB, PI3K, mTOR signal transduction pathways, and/or HIF-1alpha have the potential to inhibit VEGF expression and limit neuroblastoma tumor growth.

Brain-Derived Neurotrophic Factor↗

PubMed2004

NGF activation of TrkA decreases N-myc expression via MAPK path leading to a decrease in neuroblastoma cell number.

In neuroblastoma (NB), expression of the TrkA receptor is correlated with good prognosis while N-myc amplification is correlated with poor prognosis. Decreased N-myc levels are key to controlling growth and inducing differentiation in NB cells. In this report, we detail mechanisms by which nerve growth factor (NGF) decreases N-myc levels in TrkA-transfected NB cells and its effect on NB cell proliferation. NGF induced a decrease in N-myc mRNA within 1 h of treatment that occurred in the presence of cycloheximide. The stability of N-myc mRNA was not affected by NGF, indicating a transcriptional control of N-myc mRNA by NGF. NGF but not brain-derived neurotrophic factor (BDNF) decreased N-myc levels demonstrating that p75 alone was not involved. The NGF-induced decrease in N-myc expression was blocked by the Trk tyrosine kinase (TK) antagonist K252a indicating that signals transduced by Trk TK downstream targets were involved. Pharmacologic inhibitors implicated the mitogen-activated protein kinase (MAPK) path. This was supported by the finding that expression of a constitutively activated component of the MAPK path, MAPK kinase (MEK), decreased N-myc levels. Alterations in the level of N-myc are known to alter NB cell cycle progression by affecting the levels of E2Fs and p27(kip1). Consistent with these findings, NGF decreased NB cell number and decreased cyclin E-dependent kinase activity via an increase in p27(kip1). Thus, our results indicate that the MAP kinase is selectively involved in the NGF-induced N-myc downregulation through a transcriptional mechanism. Furthermore, NGF affects the time required for 15N TrkA cells to complete a replication cycle by decreasing N-myc, E2Fs, cyclin E kinase activity and increasing p27(kip1) binding to cyclin E kinase.

Carbazoles↗

PubMed2002

Potential use of imatinib in Ewing's Sarcoma: evidence for in vitro and in vivo activity.

BACKGROUND: Ewing's sarcoma cells express c-kit, a receptor tyrosine kinase, and its ligand, stem cell factor (SCF), creating a potential autocrine loop that may promote tumor survival. We thus examined whether the specific tyrosine kinase inhibitor imatinib mesylate (hereafter imatinib; formerly STI571) could inhibit the proliferation of Ewing's sarcoma cells in vitro and in vivo. METHODS: The effect of imatinib on c-kit expression and phosphorylation in Ewing's sarcoma cells was examined by immunoblotting. The effect of imatinib on cell growth and apoptosis was examined with an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and with a morphologic test and Annexin V staining, respectively. The effect of imatinib oral therapy (every 12 hours for 5-7 days) on primary tumor growth was assessed in Ewing's sarcoma xenografts in SCID/bg mice (5 or 10 mice per group). RESULTS: All Ewing's sarcoma cell lines tested were sensitive to imatinib-mediated apoptosis with a concentration inhibiting growth by 50% (IC50) of 10-12 micro M. Imatinib inhibited SCF-mediated c-kit phosphorylation (IC50 = 0.1-0.5 microM). In the xenograft model, imatinib treatment resulted in the regression or control of primary Ewing's sarcomas. After 6 days of treatment, the mean lower extremity volume including xenograft tumor was 3744 mm3 (95% confidence interval [CI] = 3050 to 4437 mm3), 1442 mm3 (95% CI = 931 to 1758 mm3), and 346 mm3 (95% CI = 131 to 622 mm3) in mice treated with carrier alone or with imatinib at 50 mg/kg or at 100 mg/kg, respectively. CONCLUSIONS: Imatinib interferes with growth of all Ewing's sarcoma cell lines tested in vitro and in vivo. Targeted inhibition of tyrosine kinase-dependent autocrine loops, therefore, may be a viable therapeutic strategy for Ewing's sarcoma.

Animals↗