Y K Lee

Publications (13)21.28 Total impact

• Article: Endoplasmic reticulum protein 29 regulates epithelial cell integrity during the mesenchymal-epithelial transition in breast cancer cells.

  I F Bambang, Y K Lee, D R Richardson, D Zhang
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  ABSTRACT: The epithelial-mesenchymal transition (EMT) correlates with disruption of cell-cell adhesion, loss of cell polarity and development of epithelial cell malignancy. Identifying novel molecules that inhibit EMT has profound potential for developing mechanism-based therapeutics. We previously demonstrated that the endoplasmic reticulum protein 29 (ERp29) is a novel factor that can drive mesenchymal-epithelial transition (MET) and induce cell growth arrest in MDA-MB-231 cells. Here, we show that ERp29 is an important molecule in establishing epithelial cell integrity during the MET. We demonstrate that ERp29 regulates MET in a cell context-dependent manner. ERp29 overexpression induced a complete MET in mesenchymal MDA-MB-231 cells through downregulating the expression of transcriptional repressors (for example, Slug, Snai1, ZEB2 and Twist) of E-cadherin. In contrast, overexpression of ERp29 induces incomplete MET in basal-like BT549 cells in which the expression of EMT-related markers (for example, vimentin; cytokeratin 19 (CK19) and E-cadherin) and the transcriptional repressors of E-cadherin were not altered. However, ERp29 overexpression in both cell-types resulted in loss of filamentous stress fibers, formation of cortical actin and restoration of an epithelial phenotype. Mechanistic studies revealed that overexpression of ERp29 in both cell-types upregulated the expression of TJ proteins (zonula-occludens-1 (ZO-1) and occludin) and the core apical-basal polarity proteins (Par3 and Scribble) at the membrane to enhance cell-cell contact and cell polarization. Knockdown of ERp29 in the epithelial MCF-7 cells decreased the expression of these proteins, leading to the disruption of cell-cell adhesion. Taken together, ERp29 is a novel molecule that regulates MET and epithelial cell integrity in breast cancer cells.Oncogene advance online publication, 30 April 2012; doi:10.1038/onc.2012.149.
  Oncogene 04/2012; · 6.37 Impact Factor
• Article: Different therapeutic responses in chronic obstructive pulmonary disease subgroups.

  J S Lee, J W Huh, E J Chae, J B Seo, S W Ra, J-H Lee, E-K Kim, Y K Lee, T-H Kim, W J Kim, S-M Lee, S Lee, S Y Lim, T R Shin, H I Yoon, S S Sheen, Y-M Oh, S-D Lee
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  ABSTRACT: Eleven referring hospitals in South Korea. To compare therapeutic responses in chronic obstructive pulmonary disease (COPD) subgroups, classified by diffusing capacity of the lung for carbon monoxide (DL(CO)) and lung volume. A total of 130 stable male COPD patients were classified into four subgroups according to baseline DL(CO) and residual volume/total lung capacity (RV/TLC) ratio. We compared therapeutic responses to short acting β(2)-agonist (SABA) and 3-month combined inhalation of long-acting β(2)-agonist (LABA) and corticosteroid among patients with these subgroups. Among the 130 COPD patients, 41 (31.5%) had normal DL(CO) and RV/TLC, 28 (21.5%) low DL(CO) and normal RV/TLC, 31 (23.8%) normal DL(CO) and high RV/TLC, and 30 (23.1%) low DL(CO) and high RV/TLC. The normal DL(CO)/high RV/TLC subgroup showed a significantly larger flow response (changes in forced expiratory volume in 1 s) to salbutamol than the normal DL(CO)/RV/TLC subgroups, and a larger volume response (changes in forced vital capacity) than the two normal RV/TLC subgroups. The normal DL(CO)/high RV/TLC subgroup also showed significantly larger flow and volume response to 3-month combined inhalation of LABA and corticosteroid than the two normal RV/TLC subgroups. COPD subgroups classified by DL(CO) and RV/TLC may have different pulmonary function responses to pharmacological treatment.
  The international journal of tuberculosis and lung disease: the official journal of the International Union against Tuberculosis and Lung Disease 08/2011; 15(8):1104-10. · 2.73 Impact Factor
• Article: Pulmonary artery pressure in chronic obstructive pulmonary disease without resting hypoxaemia.

  J H Lee, Y-M Oh, J B Seo, Y K Lee, W J Kim, S S Sheen, T-H Kim, E-K Kim, J S Lee, J W Huh, S Y Lim, H I Yoon, T R Shin, S-M Lee, S Y Lee, S-D Lee
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  ABSTRACT: Chronic obstructive pulmonary disease (COPD) can lead to pulmonary hypertension and cor pulmonale, which are predictors of mortality. To identify predictors of increased pulmonary artery pressure (PAP) in COPD patients without resting hypoxaemia, and to characterise COPD patients with increased PAP. A study of 117 COPD patients from the Korean Obstructive Lung Disease (KOLD) cohort who had measurable tricuspid regurgitant flow under transthoracic Doppler echocardiography and no resting hypoxaemia. The mean patient age was 67 years. Mean forced expiratory volume in 1 second (FEV(1)) was 47% predicted, mean haemoglobin (Hb) concentration was 145 g/l and mean systolic PAP (sPAP) was 33 mmHg. Multiple linear regression analysis showed that Hb was the only factor independently associated with sPAP (beta = -1.752, P = 0.005). Cluster analysis using FEV(1)% predicted, sPAP and Hb concentration as variables indicated three patient clusters: Cluster 1 (n = 36; mean FEV(1) 44% predicted, mean sPAP 39 mmHg, mean Hb 132 g/l), Cluster 2 (n = 45; FEV(1) 35% predicted, sPAP 31 mmHg, Hb 154 g/l), and Cluster 3 (n = 36; FEV(1) 65% predicted, sPAP 29 mmHg, Hb 148 g/l). Elevated PAP was linked to low haemoglobin levels in COPD without resting hypoxaemia.
  The international journal of tuberculosis and lung disease: the official journal of the International Union against Tuberculosis and Lung Disease 06/2011; 15(6):830-7. · 2.73 Impact Factor
• Conference Proceeding: A Self Evolutionary Rule-Base.

  Asad Masood Khattak, Zeeshan Pervez, W. A. Khan, S. Y. Lee, Y. K. Lee
  U- and E-Service, Science and Technology - International Conference, UNESST 2011, Held as Part of the Future Generation Information Technology Conference, FGIT 2011, in Conjunction with GDC 2011, Jeju Island, Korea, December 8-10, 2011. Proceedings; 01/2011
• Source

  Available from: Namkug Kim

  Article: Three phenotypes of obstructive lung disease in the elderly.

  K-W Jo, S W Ra, E J Chae, J B Seo, N K Kim, J-H Lee, E-K Kim, Y K Lee, T-H Kim, J W Huh, W J Kim, S-M Lee, S Y Lim, T R Shin, H I Yoon, S S Sheen, J S Lee, S-D Lee, Y-M Oh
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  ABSTRACT: Eleven referring hospitals in South Korea. To classify the phenotypes in elderly subjects with obstructive lung disease (OLD). We analysed 191 subjects aged ≥ 60 years with chronic respiratory symptoms and either obstructive spirometry or bronchial hyperresponsiveness. Factor analysis was performed using commonly measured variables and revealed four significant variables: 1) the ratio of inspiratory capacity to total lung capacity, 2) the total score on the St George's Respiratory Questionnaire, 3) the volume fraction of the lung less than 950 Hounsfield Unit at full inspiration on volumetric computed tomography and 4) post-bronchodilator forced expiratory volume in 1 second (FEV(1)) changes. We performed a cluster analysis on these four variables. The mean age was 68.5 (± 5.2 SD) years and the mean post-bronchodilator FEV(1) was 52.4% (± 16.5) predicted. Three clusters with the following phenotypes were identified: Cluster 1 included subjects with moderate to severe airflow obstruction and bronchodilator reversibility; Cluster 2 subjects had moderate airflow obstruction without bronchodilator reversibility, and Cluster 3 subjects had severe airflow obstruction without bronchodilator reversibility. We identified three phenotypes in elderly subjects with OLD. Follow-up studies are needed to explore the clinical significance of each phenotype.
  The international journal of tuberculosis and lung disease: the official journal of the International Union against Tuberculosis and Lung Disease 11/2010; 14(11):1481-8. · 2.73 Impact Factor
• Article: Radiological and clinical findings of pulmonary aspergillosis following solid organ transplant.

  Y S Park, J B Seo, Y K Lee, K H Do, J S Lee, J-W Song, K S Song
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  ABSTRACT: To evaluate the radiological and clinical findings in patients with pulmonary aspergillosis after solid organ transplantation. This study included 13 consecutive patients (five liver, four kidney, and four heart transplant; 10 male and three female; median age 54 years; range 13-63 years) with histologically confirmed pulmonary aspergillosis after solid organ transplantation at a tertiary referral hospital. Chest radiographs and computed tomography (CT) examinations performed for diagnosis were available in all patients. Radiological findings, such as lesion characteristics, location, and associated findings, were assessed retrospectively by two radiologists. The changes in radiological findings and clinical response after treatment were also assessed. Clinical findings, such as time of onset, initial symptoms, clinical course, and laboratory findings, were reviewed. The most common radiographic and CT findings were pulmonary nodules or masses (n=12). The number of nodules or masses was less than 10 in eight patients. Associated findings were surrounding ground-glass opacity (n=4), central low density (n=8), central air cavity (n=5), and air bronchogram (n=3). Follow-up radiographs and/or CT after treatment showed improvement in eight patients, persistence in two, and deterioration in three. The onset time of pulmonary aspergillosis was a median of 32 days (range 15-165 days). The most common symptom at diagnosis was fever (n=6). Ten of 13 patients did not have leucopaenia. There were two aspergillosis-associated deaths during the follow-up period. The most common radiological finding of pulmonary aspergillosis after solid organ transplantation is multiple nodules or masses, which commonly appear within 1 month following transplantation.
  Clinical Radiology 07/2008; 63(6):673-80. · 1.95 Impact Factor
• Article: Newly developed ulcer-like projection (ULP) in aortic intramural haematoma on follow-up CT: is it different from the ULP seen on the initial CT?

  Y M Jang, J B Seo, Y K Lee, E J Chae, S H Park, J-W Kang, T-H Lim
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  ABSTRACT: To show whether the clinical and radiological features of newly developed ulcer-like projections (nULPs) in an aortic intramural haematoma (IMH) on follow-up computed tomography (CT) images, are different from those of the initial ULPs (iULPs) on the initial CT images. A review of the radiological database revealed 98 patients with IMH with at least two follow-up CT examinations with a follow-up period of more than 1 month. The patients were divided into four groups: patients without iULPs or nULPs throughout the follow-up periods (group A); patients with iULPs on the initial CT images (group B); patients with nULPs on follow-up CT images but without iULPs on the initial CT images (group C); and patients with both iULPs and nULPs (group D). The type of IMH, aortic diameter, thickness of the haematoma, and complications were analysed. The clinical and CT findings and complications in the four groups were compared. Forty-two patients had no iULPs nor nULPs (group A); 27 patients had 45 iULPs on the initial CT images (group B); 16 patients had 17 nULPs on follow-up CT images without any ULP on the initial CT images (group C); and 21 nULPs developed in 13 patients with iULPs (group D). There was no significant difference in the demographic or initial CT findings in the four groups. There was no statistical difference in the incidence of complications between groups B (59.3%), group C (62.5%), and group D (69.2%; p=0.830), but there was a significant difference in the incidence of complications between the patients without any ULPs (21.5% in group A) and those with ULPs (62.5% in groups B, C, and D). There were no significant differences in the CT findings or complications between the patients with iULPs and nULPs. Regardless of the developing time of the ULPs, the incidence of complications of IMH in patients with ULPs was higher than that in those without ULPs. Careful and regular follow-up CT examinations are needed for patients with ULPs.
  Clinical Radiology 03/2008; 63(2):201-6. · 1.95 Impact Factor
• Article: A Grid‐based approach to non‐regular mesh generation for automatic remeshing with metal forming analysis

  Y. K. Lee, D. Y. Yang
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  ABSTRACT: An extension of grid-based approach with non-regular grid, as a master grid, is proposed for automatic remeshing during the finite element analysis of metal forming processes. In the proposed technique, the mesh is constructed by superimposing master grid over the object to be meshed, then taking internal cells of the grid as the elements, and finally modifying the rugged boundary with layers of surface elements and mesh smoothing. The construction method of surface element layers and the subsequent mesh smoothing technique are proposed to improve the shapes of severely distorted boundary elements. In order to verify the validity and effectiveness of the present technique, as a typical mesh generation example requiring a master grid and the finite element analysis of inner race forging is presented. Copyright © 2000 John Wiley & Sons, Ltd.
  Communications in Numerical Methods in Engineering 08/2000; 16(9):625 - 635. · 1.75 Impact Factor
• Article: Development of a grid-based mesh generation technique and its application to remeshing during the finite element simulation of a metal forming process

  Y.K. Lee, D.Y. Yang
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  ABSTRACT: An easy and robust grid-based approach is proposed to construct the fully hexahedral mesh in three-dimensional case and its application for the mesh regeneration or remeshing during the finite element simulation of a metal forming process is presented to show the validity and effectiveness of the scheme. The proposed scheme enables the construction of the provisional mesh by superimposing the regular cubical grid over the object to be meshed and removing the exterior grid points and cells. Because the constructed provisional mesh has the discrete rugged boundary that is quite different from the boundary geometry of the object to be meshed, the nodes on the boundary of the provisional mesh are projected onto the object boundary. The main disadvantage of the mesh constructed by grid-based approaches is its severely distorted elements on the boundary owing to the projection of the rugged boundary onto the object boundary. In order to improve the quality of boundary elements, some layers of elements on the boundary surface are constructed and the nodes are repositioned by mesh smoothing. Consequently, the quality of boundary elements is effectively improved.
  Engineering Computations 04/1999; 16(3):316-339. · 1.06 Impact Factor
• Article: A new method of preform design in hot forging by using electric field theory

  S.R. Lee, Y.K. Lee, C.H. Park, D.Y. Yang
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  ABSTRACT: The preform design in metal forging plays a key role in improving product quality, such as ensuring defect-free property and proper metal flow. In industry, preforms are generally designed by the iterative trial-and-error approach. This approach, however, leads not only to the increase of significant tool cost but also to the extended down-time of the production equipment. It is thus necessary to reduce time and man power through an effective method of preform design. In this paper, the equi-potential lines designed in the electric field are introduced to find an appropriate preform shape. The equi-potential lines generated between two conductors of different voltages show similar trends for the minimum work paths between the undeformed shape and the deformed shape. Based on this similarity, the equi-potential lines obtained by the arrangement of the initial and final shapes are utilized for the design of the preform, and then the artificial neural network is used to find the range of initial volume and potential value of the electric field.
  International Journal of Mechanical Sciences.
• Article: Quantitatively assessed dynamic contrast-enhanced magnetic resonance imaging in patients with chronic obstructive pulmonary disease: correlation of perfusion parameters with pulmonary function test and quantitative computed tomography

  Y. M. Jang, Y. M. Oh, J. B. Seo, N. Kim, E. J. Chae, Y. K. Lee, S. D. Lee
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  ABSTRACT: OBJECTIVES: The purpose of this study is to evaluate the correlation of the perfusion parameters of 3-dimensional, contrast-enhanced magnetic resonance (MR) imaging (3D CEMRI) with pulmonary function test (PFT) and quantitative computed tomography (CT) parameters in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: In 14 patients with COPD, 3D CEMRI was performed. From the signal intensity-time curves, pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time of each pixel was calculated. From the volumetric CT data, the quantitative parameters including the volume fraction of the lung below -950 Housefield Units (V(-950)) and mean lung density were assessed. The correlation between the MR perfusion parameters and the parameters from quantitative CT and PFT was assessed using Spearman correlation analysis. The correspondence of the regional impairment of perfusion on MR perfusion maps to the areas of emphysema on quantitative CT maps in each patient was assessed qualitatively using a 4-class visual scoring method by 2 readers. RESULTS: All 3D CEMRI examinations were successfully completed and MR perfusion parameters were obtained in all patients. The Spearman correlation test showed that PBF positively correlated with forced expiratory volume in 1 second (FEV(1))/forced vital capacity (FVC) (R = 0.49, P = 0.044), PBV positively correlated with FEV(1)/FVC (R = 0.69, P = 0.006) and negatively correlated with V-950 (R = -0.61, P = 0.020), and mean transit time positively correlated with FEV(1) (R = 0.63, P = 0.017) and FEV(1)/FVC (R = 0.76, P = 0.002). The areas of perfusion impairment on PBF and PBV maps were relatively well correlated with the areas of emphysema on CT maps [very good or good: PBF 71.5% (reader 1) and 64.3% (reader 2) of the patients, kappa = 0.47 (P < 0.001); PBV 78.6% (reader 1) and 78.6% (reader 2) of the patients, kappa = 0.89 (P < 0.001)]. CONCLUSIONS: This study shows that the deterioration of perfusion parameters measured on MR in patients with COPD, correlates with worsening of airflow limitation on PFT and emphysema index on CT. Regional heterogeneity of emphysema on CT matches with the decreased perfusion on MR.
  Invest Radiol. 43(6):403-10.
• Article: Active phase of Ni2P/SiO2 in hydroprocessing reactions

  S.T. Oyama, X. Wang, Y.-K. Lee, W.-J. Chun
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  ABSTRACT: A series of Ni2P/SiO2 catalyst samples with loading from 6 to 22 wt% Ni2P was prepared by the method of temperature-programmed reduction (TPR). The samples were characterized by BET, CO uptake, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) measurements. The activity of these catalysts was measured at 643 K and 3.1 MPa in a three-phase, packed-bed reactor for hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrodeoxygenation (HDO) using a model liquid feed containing 3000 ppm S as dibenzothiophene, 2000 ppm N as quinoline, and 500 ppm O as benzofuran. An optimum Ni2P loading for HDS, HDN, and HDO activity was found around 18 wt% which gave an HDS conversion of 99%, an HDN conversion of 91%, and an HDO conversion of 80% at a WHSV of 2.1 h−1. These were much higher than those of a commercial Ni–Mo–S/Al2O3 catalyst which gave an HDS conversion of 76%, and an HDN conversion of 38% based on equal sites (70 μmol) loaded in the reactor. The sites were counted by CO chemisorption for the phosphide and by low-temperature O2 chemisorption for the sulfide. XRD and EXAFS results confirmed that a Ni2P phase was formed on the support. The crystallite size increased slightly from 7.7 to 9.8 nm when the loading was increased, and there was evidence from CO chemisorption that some crystallite agglomeration occurred in the higher loading samples. It was found that the HDS performance did not change appreciably with Ni2P loading, but that the HDN activity and stability went through a maximum at intermediate loading. It was concluded that the HDS reaction is structure-insensitive, while the HDN reaction depends on the local arrangement of surface Ni, P, and S atoms, and is structure-sensitive. XRD and EXAFS analysis indicated that the active catalyst formed a surface phosphosulfide phase on top of a Ni2P core in the course of hydrotreating.
  Journal of Catalysis.
• Article: Development of Monte Carlo automatic modeling functions of MCAM for TRIPOLI-ITER application

  L. Lu, Y.K. Lee, J.J. Zhang, Y. Li, Q. Zeng, Y.C. Wu
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  ABSTRACT: TRIPOLI is a Monte Carlo particle transport code simulating the three-dimensional transport of neutrons and photons with the Monte Carlo method, and it can be used for many applications to nuclear devices with complex geometries; however, modeling of a complex geometry is a time-consuming and error-prone task. The recently developed functions of Monte Carlo Automatic Modeling (MCAM) system, which is an interface code that can facilitate Monte Carlo modeling by employing the CAD technology, have implemented the bidirectional conversion between the CAD model and the TRIPOLI computation model. In this study, different geometric representations of CAD system and TRIPOLI code and the methodology of bidirectional conversion between them were introduced. A TRIPOLI input file of International Thermonuclear Experimental Reactor (ITER) benchmark model, which was distributed to validate the Monte Carlo modeling tools, was created and applied to simulate D–T fusion neutron source sampling and calculate first wall loading. Then the results were compared with that of Monte Carlo N-Particle (MCNP) and the good agreements present the feasibility and validity.
  Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.