Eunju Kim

CIP2A Modulates Cell-Cycle Progression in Human Cancer Cells by Regulating the Stability and Activity of Plk1

Abnormal cell-cycle control can lead to aberrant cell proliferation and cancer. The oncoprotein cancerous inhibitor of protein phosphatase 2A (CIP2A) is an inhibitor of protein phosphatase 2A (PP2A) that stabilizes c-Myc. However, the precise role of CIP2A in cell division is not understood. Herein, we show that CIP2A is required for mitotic progression by regulating the polo-like kinase (Plk1). With mitotic entry, CIP2A translocated from the cytoplasm to the nucleus, where it was enriched at spindle poles. CIP2A depletion delayed mitotic progression, resulting in mitotic abnormalities independent of PP2A activity. Unexpectedly, CIP2A interacted directly with the polo-box domain of Plk1 during mitosis. This interaction was required to maintain Plk1 stability by blocking APC/C-Cdh1-dependent proteolysis, thereby enhancing the kinase activity of Plk1 during mitosis. We observed strong correlation and in vivo interactions between these two proteins in multiple human cancer specimens. Overall, our results established a novel function for CIP2A in facilitating the stability and activity of the pivotal mitotic kinase Plk1 in cell-cycle progression and tumor development.

Xylobiose, an Alternative Sweetener, Ameliorates Diabetes-Related Metabolic Changes by Regulating Hepatic Lipogenesis and miR-122a/33a in db/db Mice

Type 2 diabetes is a major public health concern worldwide. Xylobiose (XB) consists of two molecules of d-xylose and is a major disaccharide in xylooligosaccharides that are used as prebiotics. We hypothesized that XB could regulate diabetes-related metabolic and genetic changes via microRNA expression in db/db mice. For six weeks, C57BL/KsJ-db/db mice received 5% XB as part of the total sucrose content of their diet. XB supplementation improved glucose tolerance with reduced levels of OGTT AUC, fasting blood glucose, HbA1c, insulin, and HOMA-IR. Furthermore, XB supplementation decreased the levels of total triglycerides, total cholesterol, and LDL-C. The expression levels of miR-122a and miR-33a were higher and lower in the XB group, respectively. In the liver, expressions of the lipogenic genes, including, fatty acid synthase (FAS), peroxisome proliferator activated receptor γ (PPARγ), sterol regulatory element-binding protein-1C (SREBP-1C), sterol regulatory element-binding protein-2 (SREBP-2), acetyl-CoA carboxylase (ACC), HMG-CoA reductase (HMGCR), ATP-binding cassette transporter G5/G8 (ABCG5/8), cholesterol 7 alpha-hydroxylase (CYP7A1), and sterol 12-alpha-hydroxylase (CYP8B1), as well as oxidative stress markers, including superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), glutathione peroxidase (GPX), and catalase, were also regulated by XB supplementation. XB supplementation inhibited the mRNA expressions levels of the pro-inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1, as well as phosphorylation of c-Jun N-terminal kinase/stress activated protein kinase (JNK/SAPK), p38 mitogen-activated protein kinases (MAPK), and extracellular signal-regulated kinases 1/2 (ERK1/2). These data demonstrate that XB exhibits anti-diabetic, hypolipogenic, and anti-inflammatory effects via regulation of the miR-122a/33a axis in db/db mice.

D-Xylose as a sugar complement regulates blood glucose levels by suppressing phosphoenolpyruvate carboxylase (PEPCK) in streptozotocin-nicotinamide-induced diabetic rats and by enhancing glucose uptake in vitro

BACKGROUND/OBJECTIVES Type 2 diabetes (T2D) is more frequently diagnosed and is characterized by hyperglycemia and insulin resistance. D-Xylose, a sucrase inhibitor, may be useful as a functional sugar complement to inhibit increases in blood glucose levels. The objective of this study was to investigate the anti-diabetic effects of D-xylose both in vitro and stretpozotocin (STZ)-nicotinamide (NA)-induced models in vivo. MATERIALS/METHODS Wistar rats were divided into the following groups: (i) normal control; (ii) diabetic control; (iii) diabetic rats supplemented with a diet where 5% of the total sucrose content in the diet was replaced with D-xylose; and (iv) diabetic rats supplemented with a diet where 10% of the total sucrose content in the diet was replaced with D-xylose. These groups were maintained for two weeks. The effects of D-xylose on blood glucose levels were examined using oral glucose tolerance test, insulin secretion assays, histology of liver and pancreas tissues, and analysis of phosphoenolpyruvate carboxylase (PEPCK) expression in liver tissues of a STZ-NA-induced experimental rat model. Levels of glucose uptake and insulin secretion by differentiated C2C12 muscle cells and INS-1 pancreatic β-cells were analyzed. RESULTS In vivo, D-xylose supplementation significantly reduced fasting serum glucose levels (P < 0.05), it slightly reduced the area under the glucose curve, and increased insulin levels compared to the diabetic controls. D-Xylose supplementation enhanced the regeneration of pancreas tissue and improved the arrangement of hepatocytes compared to the diabetic controls. Lower levels of PEPCK were detected in the liver tissues of D-xylose-supplemented rats (P < 0.05). In vitro, both 2-NBDG uptake by C2C12 cells and insulin secretion by INS-1 cells were increased with D-xylose supplementation in a dose-dependent manner compared to treatment with glucose alone. CONCLUSIONS In this study, D-xylose exerted anti-diabetic effects in vivo by regulating blood glucose levels via regeneration of damaged pancreas and liver tissues and regulation of PEPCK, a key rate-limiting enzyme in the process of gluconeogenesis. In vitro, D-xylose induced the uptake of glucose by muscle cells and the secretion of insulin cells by β-cells. These mechanistic insights will facilitate the development of highly effective strategy for T2D.

Retinoic acid receptor β enhanced the anti-cancer stem cells effect of β-carotene by down-regulating expression of delta-like 1 homologue in human neuroblastoma cells

Neuroblastoma (NB) is childhood malignancy that retains characteristics of cancer stem cells (CSCs). Targeting the CSCs is one of the therapeutic strategies proposed to achieve complete remission of NB. β-carotene (BC), an active precursor of retinoids, is a well-known antioxidant reported to possess anti-CSCs effects. Here, we investigated the involvement of retinoic acid receptors (RARs) in the anti-CSCs effects of BC. Treatment with BC or retinoic acid (RA) upregulated RARβ mRNA expression in two NB cell lines. Inhibition of RARβ using siRNA up-regulated gene expression of delta-like 1 homologue (DLK1), a marker of CSCs. To understand the molecular mechanisms of RARβ-mediated inhibition of DLK1, four retinoic acid receptor elements (RAREs) were identified in the promoter of DLK1. Chromatin immunoprecipitation assays indicated that RARβ bound directly to a RARE in the DLK1 promoter region. Knock-down of RARβ also increased the self-renewal capacity of NB cells, which was suppressed by BC. Taken together, this study provided evidence that the therapeutic anti-CSC effects of BC depend on RARβ and its ability to interact with and down-regulate the CSCs marker, DLK1.

A Robust Cognitive Radio Based Adaptive Frequency/Time Spreading for OFDM Systems

The cognitive radio (CR) technology is an effective technology for a flexible use of the radio spectrum. However, the interference between the primary and the CR users becomes a critical problem for the CR system. In this paper, we propose a cognitive radio based adaptive frequency/time spreading for the orthogonal frequency division multiplexing (OFDM) systems. This new approach is characterized by the adaptive frequency spreading and time spreading, and the adaptive power control of the subcarriers at the borders of the CR users spectrum. Specifically, we propose a frequency spreading scheme according to the amount of the adjacent channel interference (ACI) coming from nearby primary users, which improves the power gain of data under severe interference. On the other hand, in order not to give an excessive interference the primary system, we also propose to reduce the power of the subcarriers near the edges of the bandwidth by spreading the signal in time. By the computer simulation, it has been proved that the proposed CR based OFDM system is very robust against ACI in comparison with the conventional OFDM system having adaptive guard bands. We also confirmed that the performance of the primary user is maintained with only a nominal degradation in the coexistence environment of the primary and CR system.

Phyllodulcin, a Natural Sweetener, Regulates Obesity-Related Metabolic Changes and Fat Browning-Related Genes of Subcutaneous White Adipose Tissue in High-Fat Diet-Induced Obese Mice

Phyllodulcin is a natural sweetener found in Hydrangea macrophylla var. thunbergii. This study investigated whether phyllodulcin could improve metabolic abnormalities in high-fat diet (HFD)-induced obese mice. Animals were fed a 60% HFD for 6 weeks to induce obesity, followed by 7 weeks of supplementation with phyllodulcin (20 or 40 mg/kg body weight (b.w.)/day). Stevioside (40 mg/kg b.w./day) was used as a positive control. Phyllodulcin supplementation reduced subcutaneous fat mass, levels of plasma lipids, triglycerides, total cholesterol, and low-density lipoprotein cholesterol and improved the levels of leptin, adiponectin, and fasting blood glucose. In subcutaneous fat tissues, supplementation with stevioside or phyllodulcin significantly decreased mRNA expression of lipogenesis-related genes, including CCAAT/enhancer-binding protein α (C/EBPα), peroxisome proliferator activated receptor γ (PPARγ), and sterol regulatory element-binding protein-1C (SREBP-1c) compared to the high-fat group. Phyllodulcin supplementation significantly increased the expression of fat browning-related genes, including PR domain containing 16 (Prdm16), uncoupling protein 1 (UCP1), and peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), compared to the high-fat group. Hypothalamic brain-derived neurotrophic factor-tropomyosin receptor kinase B (BDNF-TrkB) signaling was upregulated by phyllodulcin supplementation. In conclusion, phyllodulcin is a potential sweetener that could be used to combat obesity by regulating levels of leptin, fat browning-related genes, and hypothalamic BDNF-TrkB signaling.

Effect of vitamin C on azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colitis-associated early colon cancer in mice

BACKGROUND/OBJECTIVES The objective of this study was to investigate the effects of vitamin C on inflammation, tumor development, and dysbiosis of intestinal microbiota in an azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced inflammation-associated early colon cancer mouse model. MATERIALS/METHODS Male BALB/c mice were injected intraperitoneally with AOM [10 mg/kg body weight (b.w)] and given two 7-d cycles of 2% DSS drinking water with a 14 d inter-cycle interval. Vitamin C (60 mg/kg b.w. and 120 mg/kg b.w.) was supplemented by gavage for 5 weeks starting 2 d after the AOM injection. RESULTS The vitamin C treatment suppressed inflammatory morbidity, as reflected by disease activity index (DAI) in recovery phase and inhibited shortening of the colon, and reduced histological damage. In addition, vitamin C supplementation suppressed mRNA levels of pro-inflammatory mediators and cytokines, including cyclooxygenase-2, microsomal prostaglandin E synthase-2, tumor necrosis factor-α, Interleukin (IL)-1β, and IL-6, and reduced expression of the proliferation marker, proliferating cell nuclear antigen, compared to observations of AOM/DSS animals. Although the microbial composition did not differ significantly between the groups, administration of vitamin C improved the level of inflammation-related Lactococcus and JQ084893 to control levels. CONCLUSION Vitamin C treatment provided moderate suppression of inflammation, proliferation, and certain inflammation-related dysbiosis in a murine model of colitis associated-early colon cancer. These findings support that vitamin C supplementation can benefit colonic health. Long-term clinical studies with various doses of vitamin C are warranted.

Abstract 481: QKI, a direct target of miRNA-200, inhibits epithelial-to-mesenchymal transition

MicroRNA (miR)-200 family members are well-known regulators of epithelial-to-mesenchymal transition (EMT) in epithelial tumors. To identify novel miR-200 targets, we analyzed TargetScan and TCGA data sets. Among 20 candidate genes, we selected QKI gene and studied its role during EMT process in human head and neck squamous cell carcinoma (HNSCC) and non-small cell lung carcinoma (NSCLC) cells. The expression of QKI was proved to negatively correlate with those of miR-200 members in TCGA data sets. miR-200 suppressed QKI expression directly, which was confirmed by 39-UTR reporter assays. Interestingly, shRNA-mediated knockdown of QKI promoted migration, invasion, and EMT in cancer cells and increased tumor growth in a xenograft mouse model. These results indicate that QKI inhibits EMT and tumorigenesis in HNSCC and NSCLC cells. Even though further studies are necessary to elucidate the underlying mechanism, we suggest that QKI and miR-200 form a feedback loop to maintain homeostatic responses to EMT-inducing signals. Citation Format: Eun Ju KIM, Der Sheng Sun, Hye Sung Won, Yoon Ho Ko, Young-Ho Ahn. QKI, a direct target of miRNA-200, inhibits epithelial-to-mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 481.

Acute and 13-week subchronic toxicological evaluations of turanose in mice

BACKGROUND/OBJECTIVES Turanose, α-D-glucosyl-(1→3)-α-D-fructose, is a sucrose isomer which naturally exists in honey. To evaluate toxicity of turanose, acute and subchronic oral toxicity studies were conducted with ICR mice. MATERIALS AND METHODS For the acute oral toxicity study, turanose was administered as a single oral dose [10 g/kg body weight (b.w.)]. In the subchronic toxicity study, ICR mice were administered 0, 1.75, 3.5, and 7 g/kg b.w. doses of turanose daily for 13 weeks. RESULTS No signs of acute toxicity, including abnormal behavior, adverse effect, or mortality, were observed over the 14-day study period. In addition, no changes in body weight or food consumption were observed and the median lethal dose (LD50) for oral intake of turanose was determined to be greater than 10 g/kg b.w. General clinical behavior, changes in body weight and food consumption, absolute and relative organ weights, and mortality were not affected in any of the treatment group for 13 weeks. These doses also did not affect the macroscopic pathology, histology, hematology, and blood biochemical analysis of the mice examined. CONCLUSION No toxicity was observed in the acute and 13-week subchronic oral toxicology studies that were conducted with ICR mice. Furthermore, the no-observed-adverse-effect level is greater than 7 g/kg/day for both male and female ICR mice.

Abstract 1466: QKI, a miRNA-200 target gene, suppresses epithelial-to-mesenchymal transition in oral squamous cell carcinoma cells

Objectives: The microRNA (miR)-200 family plays a major role in specifying the epithelial phenotype by preventing expression of the transcription repressors, ZEB1 and ZEB2, which are well-known regulators of epithelial-to-mesenchymal transition (EMT) in epithelial tumors including oral squamous cell carcinoma (OSCC). Here, we elucidated whether the miR-200 family members control RNA-binding protein quaking (QKI) which is a newly identified tumor suppressor and is regulated during EMT. Methods: We predicted that miR-200a and miR-200b could recognize QKI 3’-UTR by analyzing TargetScan and TCGA head and neck SCC dataset. To further verify the role of miR-200 on QKI in HNSCC, we carried out the functional study in CAL27 and HSC3 cells. Results: Forced expression of miR-200b/a/429 inhibited the expression of ZEB1 and ZEB2, and decreased cell migration in CAL27 and HSC3 cells. QKI expression was also suppressed by miR-200 over-expression, and the 3’-UTR of QKI mRNA was directly targeted by miR-200 in luciferase reporter assays. Interestingly, shRNA-mediated knockdown of QKI led to pronounced EMT and pro-tumor effects in vitro and in vivo studies of OSCC. Conclusion: QKI increases during EMT and is targeted by miR-200; while, it suppresses EMT and tumorigenesis, contradictorily. We suggest that QKI and miR-200 could form a balancing feedback loop maintaining homeostatic responses to EMT-inducing signals. Citation Format: Yoon Ho Ko, Eun Ju Kim, Der Sheng Sun, Hye Sung Won, Young-Ho Ahn. QKI, a miRNA-200 target gene, suppresses epithelial-to-mesenchymal transition in oral squamous cell carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1466. doi:10.1158/1538-7445.AM2017-1466