Sook Young Kim

Drug-loaded gold plasmonic nanoparticles for treatment of multidrug resistance in cancer.

To investigate the possibility of treating multidrug-resistant tumors with targeted chemo-photothermal treatment, we conducted in vitro and in vivo studies using a doxorubicin (DOX)-resistant DLD-1 cell line (DLD-1/DOX) and nude mice with human xenograft tumors, respectively. The chemo-photothermal treatment consisted of DOX-loaded-poly(lactic-co-glycolic acid)-Au half-shell nanoparticles with targeting moieties of anti-death receptor-4 monoclonal antibody conjugated to the Au surface. The cells or xenografted tumors treated with nanoparticles were exposed to near infrared light for 10 min, which caused an increase in temperature to 45 °C. Chemo-photothermal treatment resulted in a large reduction in the rate of tumor xenograft growth on DLD-1/DOX tumor-bearing mice with a much smaller dose of DOX than conventional DOX chemotherapy. These results demonstrate that targeted chemo-photothermal treatment can provide high therapeutic efficacy and low toxicity in the treatment of multidrug-resistant tumors.

A Haplotype Analysis of HER-2 Gene Polymorphisms: Association with Breast Cancer Risk, HER-2 Protein Expression in the Tumor, and Disease Recurrence in Korea

Purpose: A single-nucleotide polymorphism (SNP) in codon 655 of HER-2 has been extensively studied with inconclusive results. The purpose of this study was to investigate the association between common variants of HER-2 and breast cancer risk, HER-2 expression, and survival using a haplotype-based stepwise approach. Experimental Design: Twenty-nine SNPs listed in the National Center for Biotechnology Information database were screened to identify novel polymorphisms of HER-2 gene in 90 healthy Korean women. Six of 29 SNPs were polymorphic and had greater than 10% of minor allele frequencies. Using these six SNPs, linkage disequilibrium and haplotype patterns were characterized. We tested association between the haplotypes and breast cancer in a large case–control study (n = 1,039 cases and 995 controls). Six-hundred two breast cancer patients with follow-up at least 24 months were analyzed for outcome in relation to haplotype. Expression of HER-2 protein was determined by immunohistochemistry in 1,094 cases of invasive breast cancer. Results: All six SNPs showed a strong linkage disequilibrium pattern and were considered to belong to one haplotype block. Two haplotype-tagging SNPs (I655V and P1170A) for three common haplotypes (>5%) were genotyped in cases and controls. The haplotypes and individual SNPs were not associated with breast cancer risk. In patients with at least one copy of haplotype I (the most common haplotype), HER-2 expression was 1.5 times higher (P = 0.009) and the prognosis was worse (P = 0.032) compared with patients without having that haplotype. Conclusions: Our results suggest that the currently identified genetic polymorphisms of HER-2 are not associated with an increased risk of breast cancer in Korean women, whereas one haplotype does affect protein expression of the tumor and disease outcome.

Surface plasmon-enhanced nanoscopy of intracellular cytoskeletal actin filaments using random nanodot arrays

The feasibility of super-resolution microscopy has been investigated based on random localization of surface plasmon using blocked random nanodot arrays. The resolution is mainly determined by the size of localized fields in the range of 100-150 nm. The concept was validated by imaging FITC-conjugated phalloidin that binds to cellular actin filaments. The experimental results confirm improved resolution in reconstructed images. Effect of far-field registration on image reconstruction was also analyzed. Correlation between reconstructed images was maintained to be above 81% after registration. Nanodot arrays are synthesized by temperature-annealing without sophisticated lithography and thus can be mass-produced in an extremely large substrate. The results suggest a super-resolution imaging technique that can be accessible and available in large amounts.

Capacitance-based assay for real-time monitoring of endocytosis and cell viability

Label-free cell-based assays have emerged as a promising means for high-throughput screening. Most label-free sensors are based on impedance measurements that reflect the passive electrical properties of cells. Here we introduce a capacitance-based assay that measures the dielectric constant (capacitance) of biological cells, and demonstrate the feasibility of analyzing endocytosis and screening chemotherapeutic agents with this assay. Endocytosis induces a change in the zeta potential, leading to a change in the dielectric constant which enables real-time endocytosis monitoring using the capacitance sensor. Additionally, since the dielectric constant is proportional to cell radius and cell volume, cell viability can be estimated from the change in capacitance. Therefore, the capacitance sensor array can also be used for cytotoxicity testing for large-scale chemotherapeutic screening.

Renoprotective Mechanism of Remote Ischemic Preconditioning Based on Transcriptomic Analysis in a Porcine Renal Ischemia Reperfusion Injury Model

Ischemic preconditioning (IPC) is a well-known phenomenon in which tissues are exposed to a brief period of ischemia prior to a longer ischemic event. This technique produces tissue tolerance to ischemia reperfusion injury (IRI). Currently, IPC’s mechanism of action is poorly understood. Using a porcine single kidney model, we performed remote IPC with renal IRI and evaluated the IPC mechanism of action. Following left nephrectomy, 15 female Yorkshire pigs were divided into three groups: no IPC and 90 minutes of warm ischemia (control), remote IPC immediately followed by 90 minutes of warm ischemia (rIPCe), and remote IPC with 90 minutes of warm ischemia performed 24 hours later (rIPCl). Differential gene expression analysis was performed using a porcine-specific microarray. The microarray analysis of porcine renal tissues identified 1,053 differentially expressed probes in preconditioned pigs. Among these, 179 genes had altered expression in both the rIPCe and rIPCl groups. The genes were largely related to oxidation reduction, apoptosis, and inflammatory response. In the rIPCl group, an additional 848 genes had altered expression levels. These genes were primarily related to immune response and inflammation, including those coding for cytokines and cytokine receptors and those that play roles in the complement system and coagulation cascade. In the complement system, the membrane attack complex was determined to be sublytic, because it colocalized with phosphorylated extracellular signal-regulated kinase. Furthermore, alpha 2 macroglobulin, tissue plasminogen activator, uterine plasmin trypsin inhibitor, and arginase-1 mRNA levels were elevated in the rIPCl group. These findings indicate that remote IPC produces renoprotective effects through multiple mechanisms, and these effects develop over a long timeframe rather than immediately following IPC.

Genome-wide association analysis and replication of coronary artery disease in South Korea suggests a causal variant common to diverse populations.

Background Recent genome-wide association (GWA) studies have identified and replicated several genetic loci associated with the risk of development of coronary artery disease (CAD) in samples from populations of Caucasian and Asian descent. However, only chromosome 9p21 has been confirmed as a major susceptibility locus conferring risk for development of CAD across multiple ethnic groups. The authors aimed to find evidence of further similarities and differences in genetic risk of CAD between Korean and other populations. Methods The authors performed a GWA study comprising 230 cases and 290 controls from a Korean population typed on 490u2008032 single nucleotide polymorphisms (SNPs). A total of 3148 SNPs were taken forward for genotyping in a subsequent replication study using an independent sample of 1172 cases and 1087 controls from the same population. Results The association previously observed on chromosome 9p21 was independently replicated (p=3.08e–07). Within this region, the same risk haplotype was observed in samples from both Korea and of Western European descent, suggesting that the causal mutation carried on this background occurred on a single ancestral allele. Other than 9p21, the authors were unable to replicate any of the previously reported signals for association with CAD. Furthermore, no evidence of association was found at chromosome 1q41 for risk of myocardial infarction, previously identified as conferring risk in a Japanese population. Conclusion A common causal variant is likely to be responsible for risk of CAD in Korean and Western European populations at chromosome 9p21.3. Further investigations are required to confirm non-replication of any other cross-race genetic risk factors.

TNF-α-induced Inflammation Stimulates Apolipoprotein-A4 via Activation of TNFR2 and NF-κB Signaling in Kidney Tubular Cells

Apo-A4 expression was increased in tissues from chronic kidney disease (CKD) patients compared to that in normal kidney tissue. We determined the association of apo-A4 and its regulatory signals following acute kidney injury and elucidated the effects of apo-A4 on cell signaling pathways related to kidney injury in vitro and in vivo. Tumor necrosis factor (TNF)-α, which causes inflammatory cell injury, induced significantly increased expression of apo-A4 protein levels, and these levels were related to pro-inflammatory acute kidney injury in human kidney cells. Apo-A4 expression was also increased in experimented rat kidney tissues after ischemic reperfusion injury. The expression of tumor necrosis factor receptor (TNFR) 2 was increased in both kidney cell lines and experimented rat kidney tissues following acute kidney injury. The expression of apo-A4 and TNFR2 was increased upon treatment with TNF-α. Immunohistochemistry revealed positive apo-A4 and TNFR2 staining in ischemic reperfusion injury rat kidneys compared with levels in the sham operation kidneys. After neutralization of TNF-α, NF-κB expression was only observed in the cytoplasm by immunofluorescence. Therefore, the apo-A4 expression is increased by stimulation of injured kidney cells with TNF-α and that these effects occur via a TNFR2-NFκB complex.

Exogenous pentraxin-3 inhibits the reactive oxygen species-mitochondrial and apoptosis pathway in acute kidney injury

Pentraxin-3 (PTX3) is a long-form member of the pentraxin family of proteins that has been studied in inflammatory diseases and in various organs. We found that PTX3 protects kidney cells during ischemia and proinflammatory acute kidney injury. The aim of this study was to develop an in vitro experimental model of acute kidney injury and to analyze the protective mechanism of exogenous recombinant PTX3. In this study, cells of the HK-2 renal tubular cell line were treated with a calcium ionophore (A23187), which induced injury by increasing intracellular calcium concentrations and inducing calpain activity and the generation of reactive oxygen species. Exposure of cells to PTX3 significantly attenuated these effects. In addition, the activity of caspase-3 and PARP-1 were decreased in ischemic cells exposed to exogenous recombinant PTX3. PTX3 stabilized the mitochondrial membrane potential and suppressed apoptosis, resulting in the protection of renal tubular cells from ischemic injury.

Clinical validation of serum endocan (ESM-1) as a potential biomarker in patients with renal cell carcinoma

To determine the suitability of serum endocan (ESM-1) levels for diagnosing and monitoring renal cell carcinoma (RCC), we measure serum ESM-1 levels in 56 RCC patients who had undergone radical or partial nephrectomies and 56 age- and sex-matched healthy kidney donors. Measurements were made before and 1 month and 3 months after surgery. The areas under the curve (AUCs) were determined from receiver operating characteristic (ROC) analyses. RCC patients had higher mean serum ESM-1 levels than control subjects (0.59 ± 0.07 vs. 0.52 ± 0.08 ng/mL, P < 0.001), with an AUC of 0.721 (95% CI: 0.628–0.817). In patients with tumors larger than 2 cm (n = 40) and those with clear-cell histology (n = 44), the AUCs for ESM-1 were 0.771 and 0.721, respectively. In control subjects, serum ESM-1 levels were higher in older (>50 years) individuals (P < 0.001). Among the study cohort, the AUCs for ESM-1 were 0.813 in individuals 50 years of age or younger (n = 55) and 0.637 in individuals older than 50 years (n = 57). In RCC patients, serum ESM-1 levels were reduced 1 month (P = 0.047) and 3 months (P = 0.009) after surgery. These results suggest serum ESM-1 can serve as a serologic biomarker for diagnosing and monitoring RCC, particularly in patients younger than 50 years.

High-Mobility Group Box 1-Induced Complement Activation Causes Sterile Inflammation

High-mobility group box 1 (HMGB1), a well-known danger-associated molecular pattern molecule, acts as a pro-inflammatory molecule when secreted by activated immune cells or released after necrotic cell damage. HMGB1 binds to immunogenic bacterial components and augments septic inflammation. In this study, we show how HMGB1 mediates complement activation, promoting sterile inflammation. We show that HMGB1 activates the classical pathway of complement system in an antibody-independent manner after binding to C1q. The C3a complement activation product in human plasma and C5b-9 membrane attack complexes on cell membrane surface are detected after the addition of HMGB1. In an acetaminophen (APAP)-induced hepatotoxicity model, APAP injection reduced HMGB1 levels and elevated C3 levels in C1q-deficient mouse serum samples, compared to that in wild-type (WT) mice. APAP-induced C3 consumption was inhibited by sRAGE treatment in WT mice. Moreover, in a mouse model of brain ischemia–reperfusion injury based on middle cerebral arterial occlusion, C5b-9 complexes were deposited on vessels where HMGB1 was accumulated, an effect that was suppressed upon HMGB1 neutralization. We propose that the HMGB1 released after cell necrosis and in ischemic condition can trigger the classical pathway of complement activation to exacerbate sterile inflammation.