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1.  Clinical utilization of cord blood over human health: experience of stem cell transplantation and cell therapy using cord blood in Korea 
Korean Journal of Pediatrics  2014;57(3):110-116.
Cord blood (CB) has been used as an important and ethical source for hematopoietic stem cell transplantation (SCT) as well as cell therapy by manufacturing mesenchymal stem cell, induced pleuripotential stem cell or just isolating mononuclear cell from CB. Recently, the application of cell-based therapy using CB has expanded its clinical utility, particularly, by using autologous CB in children with refractory diseases. For these purposes, CB has been stored worldwide since mid-1990. In this review, I would like to briefly present the historical development of clinical uses of CB in the fields of SCT and cell therapy, particularly to review the experiences in Korea. Furthermore, I would touch the recent banking status of CB.
PMCID: PMC4000756  PMID: 24778692
Cord blood; Transplantation; Cell therapy
2.  NMR Characterization of the Interaction of the Endonuclease Domain of MutL with Divalent Metal Ions and ATP 
PLoS ONE  2014;9(6):e98554.
MutL is a multi-domain protein comprising an N-terminal ATPase domain (NTD) and C-terminal dimerization domain (CTD), connected with flexible linker regions, that plays a key role in DNA mismatch repair. To expand understanding of the regulation mechanism underlying MutL endonuclease activity, our NMR-based study investigated interactions between the CTD of MutL, derived from the hyperthermophilic bacterium Aquifex aeolicus (aqMutL-CTD), and putative binding molecules. Chemical shift perturbation analysis with the model structure of aqMutL-CTD and circular dichroism results revealed that tight Zn2+ binding increased thermal stability without changing secondary structures to function at high temperatures. Peak intensity analysis exploiting the paramagnetic relaxation enhancement effect indicated the binding site for Mn2+, which shared binding sites for Zn2+. The coexistence of these two metal ions appears to be important for the function of MutL. Chemical shift perturbation analysis revealed a novel ATP binding site in aqMutL-CTD. A docking simulation incorporating the chemical shift perturbation data provided a putative scheme for the intermolecular interactions between aqMutL-CTD and ATP. We proposed a simple and understandable mechanical model for the regulation of MutL endonuclease activity in MMR based on the relative concentrations of ATP and CTD through ATP binding-regulated interdomain interactions between CTD and NTD.
PMCID: PMC4047009  PMID: 24901533
3.  Responsiveness of the Korean Version of the Michigan Hand Outcomes Questionnaire after Carpal Tunnel Release 
Clinics in Orthopedic Surgery  2014;6(2):203-207.
The Korean version of the Michigan Hand Outcomes Questionnaire (K-MHQ) was recently validated; however, the questionnaire's responsiveness as well as the degree to which the instrument is sensitive to change has not been thoroughly evaluated in a specific condition in Koreans. We evaluated the responsiveness of the K-MHQ in a homogenous cohort of patients with carpal tunnel syndrome (CTS) and we compared it with that of the Korean version of the Disability of the Arm, Shoulder, and Hand Questionnaire (K-DASH), which was found to have a large degree of responsiveness after carpal tunnel release for Korean patients with CTS.
Thirty-seven patients with CTS prospectively completed the K-MHQ and the K-DASH before and 6 months after surgery. The responsiveness statistics were assessed for both the K-MHQ and the K-DASH by using the standardized response mean (SRM), which was defined as the mean change of the original scores after surgery divided by the standard deviation of the change.
All domains of the K-MHQ significantly improved after carpal tunnel release (p < 0.001). The SRM for all scales but one (the aesthetics scale) showed large responsiveness of ≥ 0.8. The aesthetics scale showed medium responsiveness of 0.6. The combined function/symptom scale of the K-DASH significantly improved after surgery (p < 0.001). The SRM of the K-DASH revealed large responsiveness of 0.9.
The K-MHQ was found to have a large degree of responsiveness after carpal tunnel release for Korean patients with CTS, which is comparable not only to the K-DASH, but also to the original version of the MHQ. The region-specific K-MHQ can be useful for outcomes research related to carpal tunnel surgery, especially for research comparing CTS with various other hand and wrist health conditions.
PMCID: PMC4040382  PMID: 24900903
Responsiveness; K-MHQ; K-DASH; Carpal tunnel syndrome
4.  Clinical characteristics of hemophagocytic lymphohistiocytosis following Kawasaki disease: differentiation from recurrent Kawasaki disease 
Blood research  2013;48(4):254-257.
Our aim was to investigate the clinical pattern of hemophagocytic lymphohistiocytosis following Kawasaki disease (HLH-KD), to enable differentiation of HLH from recurrent or refractory KD and facilitate early diagnosis.
We performed a nationwide retrospective survey and reviewed the clinical characteristics of patients with HLH-KD, including the interval between KD and HLH, clinical and laboratory findings, treatment responses, and outcomes, and compared them with historical data for both diseases.
Twelve patients with HLH-KD, including 5 previously reported cases, were recruited. The median age was 6.5 years (range, 9 months-14.7 years). Eight patients were male and 4 were female. The median interval between the first episode of KD and the second visit with recurrent fever was 12 days (3-22 days). Of the 12 children, 2 were initially treated with intravenous IgG (IVIG) for recurrent KD when they presented at the hospital with recurrent fever. Eventually, 10 children received chemotherapy under an HLH protocol and 2 received supportive treatment. Two patients died of combined infections during chemotherapy, 1 was lost to follow up, and 9 remain alive. The overall survival rate at 4 years was 81.1% with a median follow up of 45.1 months.
A diagnosis of HLH-KD should be considered when symptoms similar to recurrent KD develop within 1 month of the first episode of KD. Our findings will help physicians differentiate between HLH and the recurrent form of KD.
PMCID: PMC3894383  PMID: 24466549
Hemophagocytic lymphohistiocytosis; Kawasaki disease; Recurrent
5.  Meta-analysis of randomized controlled trials of bosentan for treatment of pulmonary arterial hypertension 
We assessed the efficacy and safety of bosentan in patients with pulmonary arterial hypertension (PAH).
We surveyed randomized controlled trials (RCTs) of the efficacy and safety of bosentan in patients with PAH using MEDLINE, EMBASE, the Cochrane Controlled Trials Register, and manual searches. Meta-analysis of RCTs was performed to determine treatment efficacy and safety outcomes. Results are presented as odds ratios (ORs) or weighted mean differences (WMDs).
Meta-analysis of seven RCTs including a total of 410 patients and 296 controls revealed that the 6-minute work distance was significantly higher in the bosentan group than in the placebo group (WMD, 46.19; 95% confidence interval [CI], 21.20 to 71.19; p = 2.9 × 10-5). Compared with the placebo, bosentan significantly reduced the mean pulmonary arterial pressure in patients with PAH (WMD, -6.026; 95% CI, -8.785 to -3.268, p = 1.8 × 10-6). The bosentan therapy group worsened less clinically than the placebo group (OR, 0.252; 95% CI, 0.140 to 0.454; p = 4.6 × 10-7). The incidence of serious adverse events did not differ between the bosentan and placebo groups (OR, 0.948; 95% CI, 0.556 to 1.614; p = 0.843). However, the results of the abnormal liver function test (LFT) were significantly higher in the bosentan group than in the placebo group (OR, 2.312; 95% CI, 1.020 to 5.241; p = 0.045).
This meta-analysis shows that bosentan can treat PAH effectively. However, bosentan increased the incidence of abnormal LFT results compared with the placebo.
PMCID: PMC3846996  PMID: 24307846
Bosentan; Efficacy; Safety; Hypertension, pulmonary
6.  Nrf2 Negatively Regulates Melanogenesis by Modulating PI3K/Akt Signaling 
PLoS ONE  2014;9(4):e96035.
Nrf2 plays a role in protection of cells against oxidative stress and xenobiotic damage by regulating cytoprotective genes. In this study, we investigated the effect of Nrf2 on melanogenesis in normal human melanocytes (NHMCs). When NHMCs were transduced with a recombinant adenovirus expressing Nrf2, melanin synthesis was significantly decreased. Consistent with this result, overexpression of Nrf2 decreased the expression of tyrosinase and tyrosinase-related protein 1. The inhibitory effect of Nrf2 was reversed by overexpression of Keap1, an intracellular regulator of Nrf2. Interestingly, Nrf2 overexpression resulted in marked activation of PI3K/Akt signaling. Conversely, inhibition of PI3K activity by treatment with wortmannin reversed the depigmentary effects of Nrf2. Taken together, these results strongly suggest that Nrf2 negatively regulates melanogenesis by modulating the PI3K/Akt signaling pathway.
PMCID: PMC3999113  PMID: 24763530
8.  Effect of Human Parathyroid Hormone on Hematopoietic Progenitor Cells in NOD/SCID Mice Co-Transplanted with Human Cord Blood Mononuclear Cells and Mesenchymal Stem Cells 
Yonsei Medical Journal  2012;54(1):238-245.
We evaluated the effect of human parathyroid hormone (hPTH) on the engraftment and/or in vivo expansion of hematopoietic stem cells in an umbilical cord blood (UCB)-xenotransplantation model. In addition, we assessed its effect on the expression of cell adhesion molecules.
Materials and Methods
Female NOD/SCID mice received sublethal total body irradiation with a single dose of 250 cGy. Eighteen to 24 hours after irradiation, 1×107 human UCB-derived mononuclear cells (MNCs) and 5×106 human UCB-derived mesenchymal stem cells (MSCs) were infused via the tail vein. Mice were randomly divided into three groups: Group 1 mice received MNCs only, Group 2 received MNCs only and were then treated with hPTH, Group 3 mice received MNCs and MSCs, and were treated with hPTH.
Engraftment was achieved in all the mice. Bone marrow cellularity was approximately 20% in Group 1, but 70-80% in the hPTH treated groups. Transplantation of MNCs together with MSCs had no additional effect on bone marrow cellularity. However, the proportion of human CD13 and CD33 myeloid progenitor cells was higher in Group 3, while the proportion of human CD34 did not differ significantly between the three groups. The proportion of CXCR4 cells in Group 3 was larger than in Groups 1 and 2 but without statistical significance.
We have demonstrated a positive effect of hPTH on stem cell proliferation and a possible synergistic effect of MSCs and hPTH on the proportion of human hematopoietic progenitor cells, in a xenotransplantation model. Clinical trials of the use of hPTH after stem cell transplantation should be considered.
PMCID: PMC3521258  PMID: 23225826
Umbilical cord blood; parathyroid hormone; bone marrow niches
9.  Role of Endogenous ENaC and TRP Channels in the Myogenic Response of Rat Posterior Cerebral Arteries 
PLoS ONE  2013;8(12):e84194.
Mechanogated ion channels are predicted to mediate pressure-induced myogenic vasoconstriction in small resistance arteries. Recent findings have indicated that transient receptor potential (TRP) channels and epithelial sodium channels (ENaC) are involved in mechanotransduction. The purpose of this study was to investigate the role of TRP channels and ENaC in the myogenic response. Our previous study suggested that ENaC could be a component of the mechanosensitive ion channels in rat posterior cerebral arteries (PCA). However, the specific ion channel proteins mediating myogenic constriction are unknown. Here we found, for the first time, that ENaC interacted with TRPM4 but not with TRPC6 using immunoprecipitation and confocal microscopy.
Methods and Results
Treatment with a specific βENaC inhibitor, amiloride, a specific TRPM4 inhibitor, 9-phenanthrol, and a TRPC6 inhibitor, SKF96365, resulted in inhibition of the pressure-induced myogenic response. Moreover, the myogenic response was inhibited in rat PCA transfected with small interfering RNA of βENaC, TRPM4, and TRPC6. Co-treatment with amiloride and 9-phenanthrol showed a similar inhibitory effect on myogenic contraction compared to single treatment with amiloride or 9-phenanthrol. The myogenic response was not affected by 9-phenanthrol or amiloride treatment in PCA transfected with βENaC or TRPM4 siRNA, respectively. However, pressure-induced myogenic response was fully inhibited by co-treatment with amiloride, 9-phenanthrol, and SKF96365, and by treatment with SKF96365 in PCA transfected with βENaC siRNA.
Our results suggest that ENaC, TRPM4, and TRPC6 play important roles in the pressure-induced myogenic response, and that ENaC and TRPM4 interact in rat PCA.
PMCID: PMC3877230  PMID: 24391909
10.  Thromboembolic events identified during diagnosis of germ cell tumors in 2 children 
The Korean Journal of Hematology  2012;47(3):233-236.
We describe 2 cases in which radiographic evidence of thromboembolic events was obtained during germ cell tumor diagnosis. There was no evidence of coagulation factor abnormalities or contributory procedures or drugs in either patient. We used anticoagulation therapy for thrombolysis in one patient, but in the other, the thromboembolism resolved spontaneously.
PMCID: PMC3464343  PMID: 23071481
Thromboembolism; Germ cell tumor; Chemotherapy
11.  Enactment of a Law for Governmental Support of the Use of Cord Blood, and Ethical Issues 
In Korea, cord blood banking projects have been developed since 1996, and the 1st successful cord blood transplant was performed in 1998. Recently, “Cord Blood Management and Research Act” was legislated in 2010, and has been come into effect on July 1st, 2011. This review focuses the backgrounds, aims, and legislation process as well as principal articles in this act.
PMCID: PMC3840985  PMID: 24298360
Cord blood; Act
12.  Inflammatory Responses in the Muscle Coat of Stomach and Small Bowel in the Postoperative Ileus Model of Guinea Pig 
Yonsei Medical Journal  2013;54(6):1336-1341.
Small intestinal function returns first after surgery, and then the function of the stomach returns to normal after postoperative ileus (POI). The aim of this study was to investigate inflammatory responses in the muscle coat of stomach and small intestine in guinea pig POI model.
Materials and Methods
The distance of charcoal migration from pylorus to the distal intestine was measured. Hematoxylin and eosin (H&E) and immunohistochemical stain for calprotectin were done from the histologic sections of stomach, jejunum and ileum obtained at 3 and 6 hour after operation. Data were compared between sham operation and POI groups.
The distance of charcoal migration was significantly reduced in the 3 and 6 hour POI groups compared with sham operated groups (p<0.05). On H&E staining, the degree of inflammation was significantly higher in the stomach of 3 hour POI groups compared with jejunum and ileum of POI groups or sham operated groups (p<0.05). Calprotectin positive cells were significantly increased in the muscle coat of stomach of 3 hour POI groups compared with jejunum and ileum of POI groups or sham operated groups (p<0.05). There was strong association between the degree of inflammation and calprotectin positive cells in stomach.
Postoperative ileus induced by cecal manipulation significantly increased the degree of inflammation and calprotectin positive cells in the muscle coat of stomach as a remote organ. The relevance of degree of inflammation and the recovery time of ileus should be pursued in the future research.
PMCID: PMC3809856  PMID: 24142636
Postoperative ileus; stomach; small intestine; calprotectin
13.  Roles of protein arginine methylation in DNA damage signaling pathways 
Cell Cycle  2011;10(9):1343-1344.
PMCID: PMC3117038  PMID: 21445011
BRCA1; p300; CARM1; DNA damage; protein methylation; p21; Gadd45; cell cycle; apoptosis; cancer
14.  Triple disruption of the superior shoulder suspensory complex 
The superior shoulder suspensory complex (SSSC) is an extremely important structure composed of a ring of bone and soft tissues at the superior aspect of the shoulder. Double disruption leads to instability of the construct and usually requires operative treatment. Triple disruption of the SSSC is extremely rare and is encountered in high-energy trauma cases often in association with other injuries. The authors experienced a case of triple disruption involving the acromion, coracoid process, and acromioclavicular separation. This type of SSSC disruption is unlikely to have been caused by a single impact and is rather caused by multiple impacts during one traumatic event.
PMCID: PMC3391788  PMID: 22787337
Superior shoulder suspensory complex; SSSC; triple disruption
15.  Roles of TLR7 in Activation of NF-κB Signaling of Keratinocytes by Imiquimod 
PLoS ONE  2013;8(10):e77159.
Imiquimod is known to exert its effects through Toll-like receptor 7 (TLR7) and/or TLR8, resulting in expression of proinflammatory cytokines and chemokines. Keratinocytes have not been reported to constitutively express TLR7 and TLR8, and the action of imiquimod is thought to be mediated by the adenine receptor, not TLR7 or TLR8. In this study, we revealed the expression of TLR7 in keratinocytes after calcium-induced differentiation. After addition of calcium to cultured keratinocytes, the immunological responses induced by imiquimod, such as activation of NF-κB and induction of TNF-α and IL-8, were more rapid and stronger. In addition, imiquimod induced the expression TLR7, and acted synergistically with calcium to induce proinflammatory cytokines. We confirmed that the responses induced by imiquimod were significantly inhibited by microRNAs suppressing TLR7 expression. These results suggest that TLR7 expressed in keratinocytes play key roles in the activation of NF-κB signaling by imiquimod, and that their modulation in keratinocytes could provide therapeutic potential for many inflammatory skin diseases.
PMCID: PMC3795621  PMID: 24146965
16.  TXNIP Deficiency Exacerbates Endotoxic Shock via the Induction of Excessive Nitric Oxide Synthesis 
PLoS Pathogens  2013;9(10):e1003646.
Thioredoxin-interacting protein (TXNIP) has multiple functions, including tumor suppression and involvement in cell proliferation and apoptosis. However, its role in the inflammatory process remains unclear. In this report, we demonstrate that Txnip−/− mice are significantly more susceptible to lipopolysaccharide (LPS)-induced endotoxic shock. In response to LPS, Txnip−/− macrophages produced significantly higher levels of nitric oxide (NO) and inducible nitric oxide synthase (iNOS), and an iNOS inhibitor rescued Txnip−/− mice from endotoxic shock-induced death, demonstrating that NO is a major factor in TXNIP-mediated endotoxic shock. This susceptibility phenotype of Txnip−/− mice occurred despite reduced IL-1β secretion due to increased S-nitrosylation of NLRP3 compared to wild-type controls. Taken together, these data demonstrate that TXNIP is a novel molecule that links NO synthesis and NLRP3 inflammasome activation during endotoxic shock.
Author Summary
TXNIP has many biological functions, including the inhibition of tumor growth, suppression of hepatocarcinogenesis, and regulation of glucose metabolism and reactive oxygen species (ROS) generation in different cell types. However, little is known about its role in the inflammatory process. In this study, our results demonstrate that TXNIP plays a critical role in the control of lethal endotoxin-induced shock by controlling NO production in innate immune cells via the regulation of iNOS expression. This regulation is mediated through changes in the activation and translocation of NF-κB that affect the NF-κB/iNOS pathway. In addition, excessive NO reduces the production of IL-1β via S-nitrosylation of the NLRP3 inflammasome. Subsequently, the survival of Txnip−/− mice is significantly decreased due to hypothermia and hypoglycemia. Overall, these results suggest that TXNIP is a novel therapeutic target for the treatment of inflammatory diseases.
PMCID: PMC3789754  PMID: 24098117
17.  Structure, Folding Dynamics, and Amyloidogenesis of D76N β2-Microglobulin 
The Journal of Biological Chemistry  2013;288(43):30917-30930.
Background: We recently discovered the first natural human β2-microglobulin variant, D76N, as an amyloidogenic protein.
Results: Fluid flow on hydrophobic surfaces triggers its amyloid fibrillogenesis. The α-crystallin chaperone inhibits variant-mediated co-aggregation of wild type β2-microglobulin.
Conclusion: These mechanisms likely reflect in vivo amyloidogenesis by globular proteins in general.
Significance: Our results elucidate the molecular pathophysiology of amyloid deposition.
Systemic amyloidosis is a fatal disease caused by misfolding of native globular proteins, which then aggregate extracellularly as insoluble fibrils, damaging the structure and function of affected organs. The formation of amyloid fibrils in vivo is poorly understood. We recently identified the first naturally occurring structural variant, D76N, of human β2-microglobulin (β2m), the ubiquitous light chain of class I major histocompatibility antigens, as the amyloid fibril protein in a family with a new phenotype of late onset fatal hereditary systemic amyloidosis. Here we show that, uniquely, D76N β2m readily forms amyloid fibrils in vitro under physiological extracellular conditions. The globular native fold transition to the fibrillar state is primed by exposure to a hydrophobic-hydrophilic interface under physiological intensity shear flow. Wild type β2m is recruited by the variant into amyloid fibrils in vitro but is absent from amyloid deposited in vivo. This may be because, as we show here, such recruitment is inhibited by chaperone activity. Our results suggest general mechanistic principles of in vivo amyloid fibrillogenesis by globular proteins, a previously obscure process. Elucidation of this crucial causative event in clinical amyloidosis should also help to explain the hitherto mysterious timing and location of amyloid deposition.
PMCID: PMC3829406  PMID: 24014031
Amyloid; Protein Aggregation; Protein Misfolding; Protein Stability; Shear Stress; D76N β2-Microglobulin; Chaperones; Systemic Amyloidosis
18.  Marked Acceleration of Atherosclerosis following Lactobacillus casei induced Coronary Arteritis in a Mouse Model of Kawasaki Disease 
To investigate if Lactobacillus casei cell wall extract (LCWE)-induced Kawasaki Disease (KD) accelerates atherosclerosis in hypercholesterolemic mice.
Method and Resuslts
Apoe−/− or Ldlr−/− mice were injected with LCWE (KD mice) or PBS, fed high fat diet for 8 weeks, and atherosclerotic lesions in aortic sinuses (AS), arch (AC) and whole aorta were assessed. KD mice had larger, more complex aortic lesions with abundant collagen, and both extracellular and intracellular lipid and foam cells, compared to lesions in control mice despite similar cholesterol levels. Both Apoe−/− KD and Ldlr−/− KD mice showed dramatic acceleration in atherosclerosis vs. controls, with increases in en face aortic atherosclerosis and plaque size in both the AS and AC plaques. Accelerated atherosclerosis was associated with increased circulating IL-12p40, IFN-γ, TNF-α, and increased macrophage, DC, and T cell recruitment in lesions. Furthermore, daily injections of the IL-1Ra, which inhibits LCWE induced KD vasculitis, prevented the acceleration of atherosclerosis.
Our results suggest an important pathophysiologic link between coronary arteritis/vasculitis in the KD mouse model and subsequent atherosclerotic acceleration, supporting the concept that a similar relation may also be present in KD patients. These results also suggest that KD in childhood may predispose to accelerated and early atherosclerosis as adults.
PMCID: PMC3480341  PMID: 22628430
atherosclerosis; coronary disease; Kawasaki Disease; Interleukin 1 beta; IL-1 Receptor antagonist; mouse model of Kawasaki; vasculitis
19.  Proteomic Evaluation of Acquired Enamel Pellicle during In Vivo Formation 
PLoS ONE  2013;8(7):e67919.
Acquired enamel pellicle (AEP) is a protein film that forms on the enamel surface of teeth by selective adsorption of proteins and peptides present in the mouth. This protein film forms the interface between enamel and the damage oral biofilm, which modulates the attachment of bacteria found in oral biofilm. The overall goal of this study was to gain insight into the biological formation of the human in vivo AEP. This study hypothesized that AEP is created by the formation of successive protein layers, which consist of initial binding to enamel and subsequent protein-protein interactions. This hypothesis was examined by observing quantitative and qualitative changes in pellicle composition during the first two hours of AEP formation in the oral cavity. Quantitative mass spectrometry approaches were used to generate an AEP protein profile for each time-point studied. Relative proteomic quantification was carried out for the 50 proteins observed in all four time-points. Notably, the abundance of important salivary proteins, such as histatin 1, decrease with increasing of the AEP formation, while other essential proteins such as statherin showed constant relative abundance in all time-points. In summary, this is the first study that investigates the dynamic process to the AEP formation by using proteomic approaches. Our data demonstrated that there are significant qualitative and quantitative proteome changes during the AEP formation, which in turn will likely impact the development of oral biofilms.
PMCID: PMC3700865  PMID: 23844127
20.  What is different about medical students interested in non-clinical careers? 
BMC Medical Education  2013;13:81.
The proportion of medical school graduates who pursue careers other than full-time clinical practice has increased in some countries as the physician’s role has evolved and diversified with the changing landscape of clinical practice and the advancement of biomedicine. Still, past studies of medical students’ career choices have focused on clinical specialties and little is known about their choice of non-clinical careers. The present study examined backgrounds, motivation and perceptions of medical students who intended non-clinical careers.
A questionnaire was administered to students at six Korean medical schools distributed across all provinces in the nation. The questionnaire comprised 40 items on respondents’ backgrounds, their motivation for and interest in the study of medicine, their perceptions of medical professions, and their career intentions. Data was analyzed using various descriptive and inferential statistics.
In total, 1,388 students returned the questionnaire (60% response rate), 12.3% of whom intended non-clinical careers (i.e., basic sciences, non-clinical medical fields, and non-medical fields). Those who planned non-clinical careers were comparable with their peers in their motivation for studying medicine and in their views of medical professions, but they were less interested in the study of medicine (P < 0.01). The two groups also differed significantly on their perceptions of what was uninteresting about the study of medicine (P < 0.01). The two groups were comparable in gender and entry-level ratios but their distributions across ages and years of study differed significantly (P < 0.01). A majority of respondents agreed with the statements that “it is necessary for medical school graduates to pursue non-clinical careers” and that “medical schools need to offer programs that provide information on such careers.” Still, our finding indicates that medical school curricula do not address such needs sufficiently.
Our study found some differences in backgrounds and perceptions of the study of medicine in medical students interested in non-clinical careers from their peers. Future studies are suggested to enhance our understanding of medical students” choice of non-clinical careers.
PMCID: PMC3679731  PMID: 23731551
21.  Implication of Cord Blood for Cell-Based Therapy in Refractory Childhood Diseases 
Since cord blood (CB) contains hematopoietic stem cells as well as a mixture of multipotent stem cells, CB has the ability to give rise to hematopoietic, epithelial, endothelial and neural tissues. Recently, the application of cell-based therapy using CB has expanded its clinical utility, particularly, by using autologous CB in children with refractory diseases. This review focuses clinical and pre-clinical application of CB cell-based therapy for inherited metabolic diseases as well as tissue regenerations in neonatal hypoxic-ischemic encephalopathy, cerebral palsy, and juvenile diabetes.
PMCID: PMC4022686  PMID: 24855537
Cord blood; Stem cells; Regenerative medicine
23.  HP1 promotes tumor suppressor BRCA1 functions during the DNA damage response 
Nucleic Acids Research  2013;41(11):5784-5798.
The DNA damage response (DDR) involves both the control of DNA damage repair and signaling to cell cycle checkpoints. Therefore, unraveling the underlying mechanisms of the DDR is important for understanding tumor suppression and cellular resistance to clastogenic cancer therapeutics. Because the DDR is likely to be influenced by chromatin regulation at the sites of DNA damage, we investigated the role of heterochromatin protein 1 (HP1) during the DDR process. We monitored double-strand breaks (DSBs) using the γH2AX foci marker and found that depleting cells of HP1 caused genotoxic stress, a delay in the repair of DSBs and elevated levels of apoptosis after irradiation. Furthermore, we found that these defects in repair were associated with impaired BRCA1 function. Depleting HP1 reduced recruitment of BRCA1 to DSBs and caused defects in two BRCA1-mediated DDR events: (i) the homologous recombination repair pathway and (ii) the arrest of cell cycle at the G2/M checkpoint. In contrast, depleting HP1 from cells did not affect the non-homologous end-joining (NHEJ) pathway: instead it elevated the recruitment of the 53BP1 NHEJ factor to DSBs. Notably, all three subtypes of HP1 seemed to be almost equally important for these DDR functions. We suggest that the dynamic interaction of HP1 with chromatin and other DDR factors could determine DNA repair choice and cell fate after DNA damage. We also suggest that compromising HP1 expression could promote tumorigenesis by impairing the function of the BRCA1 tumor suppressor.
PMCID: PMC3675466  PMID: 23589625
24.  Antibiotic-induced Severe Neutropenia with Multidrug-Dependent Antineutrophil Antibodies Developed in A Child with Streptococcus pneumoniae Infection 
Journal of Korean Medical Science  2009;24(5):975-978.
Drug-induced neutropenia (DIN), particularly that in which antibiotic-dependent antineutrophil antibodies have been detected, is a rare disorder. We report the case of a child with pneumococcal pneumonia, who experienced severe neutropenia during various antibiotic treatments. We detected 4 kinds (cefotaxim, augmentin, vancomycin, and tobramycin) of antibiotic-dependent antineutrophil antibodies by using the mixed passive hemagglutination assay (MPHA) technique with this child.
PMCID: PMC2752789  PMID: 19795004
Neutropenia; Antineutrophil Antibody; Anti-Bacterial Agents
25.  Cancer vaccination drives Nanog-dependent evolution of tumor cells towards an immune-resistant and stem-like phenotype 
Cancer Research  2012;72(7):1717-1727.
Due to the exquisite specificity and potency of the immune system, vaccination is in theory the most precise and powerful approach for controlling cancer. However, current data from clinical trials indicate that vaccination rarely yields significant benefits for cancer patients in terms of tumor progression and long-term survival. The poor clinical outcomes of vaccination are primarily caused by mechanisms of immune tolerance, especially within the tumor microenvironment. Here we report that vaccination drives the evolution of tumor cells towards an immune-resistant and stem-like phenotype that promotes tumor growth and nullifies the cytotoxic T lymphocyte (CTL) response. The emergence of this phenotype required the transcription factor Nanog, which is induced as a consequence of immune selection. Nanog expression enhanced the stem-like features of tumor cells and protected them from killing by tumor-reactive CTLs. Delivery of siNanog into tumor-bearing mice rendered the tumor vulnerable to immune surveillance and strongly suppressed its growth. Together, our findings demonstrate tumor adaptation to vaccination through gain of an immune-resistant, stem-like phenotype and identify Nanog as a central molecular target in this process. Future vaccination technology should consider Nanog an important target to enhance the immunotherapeutic response.
PMCID: PMC3319841  PMID: 22337995
Cancer stem cell; immune escape; vaccination; human papillomavirus (HPV)

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