• BMB Reports
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• v.52 no.1
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• pp.70-85
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• 2019

Reduction of insulin/insulin-like growth factor 1 (IGF1) signaling (IIS) extends the lifespan of various species. So far, several longevity mouse models have been developed containing mutations related to growth signaling deficiency by targeting growth hormone (GH), IGF1, IGF1 receptor, insulin receptor, and insulin receptor substrate. In addition, p70 ribosomal protein S6 kinase 1 (S6K1) knockout leads to lifespan extension. S6K1 encodes an important kinase in the regulation of cell growth. S6K1 is regulated by mechanistic target of rapamycin (mTOR) complex 1. The v-myc myelocytomatosis viral oncogene homolog (MYC)-deficient mice also exhibits a longevity phenotype. The gene expression profiles of these mice models have been measured to identify their longevity mechanisms. Here, we summarize our knowledge of long-lived mouse models related to growth and discuss phenotypic characteristics, including organ-specific gene expression patterns.

• BMB Reports
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• v.53 no.7
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• pp.373-378
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• 2020

Phosphorylation of the signaling component by protein kinase often leads to a kinase cascade or feedback loop. 3-Phosphoinositide-dependent kinase 1 (PDK1) signaling pathway diverges into various kinases including Akt and p70 S6 kinase (p70S6k). However, the PDK1 feedback mechanism remains elusive. Here, we demonstrated that UNC-51-like kinase (ULK1), an autophagy initiator kinase downstream of mechanistic target of rapamycin (mTOR), directly phosphorylated PDK1 on serine 389 at the linker region. Furthermore, our data showed that this phosphorylation affected the kinase activity of PDK1 toward downstream substrates. These results suggest a possible negative feedback loop between PDK1 and ULK1.

• Journal of Applied Biological Chemistry
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• v.58 no.3
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• pp.219-226
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• 2015

The anticancer activity of a methanolic extract from lemon leaves (MLL) was assessed in MCF-7-SC human breast cancer stem cells. MLL induced apoptosis in MCF-7-SC, as evidenced by increased apoptotic body formation, sub-G1 cell population, annexin V-positive cells, Bax/Bcl-2 ratio, as well as proteolytic activation of caspase-9 and caspase-3, and degradation of poly (ADP-ribose) polymerase (PARP) protein. Concomitantly, MLL induced the formation of acidic vesicular organelles, increased LC3-II accumulation, and reduced the activation of Akt, mTOR, and p70S6K, suggesting that MLL initiates an autophagic progression in MCF-7-SC via the Akt/mTOR pathway. Epithelial-mesenchymal transition (EMT), a critical step in the acquisition of the metastatic state, is an attractive target for therapeutic interventions directed against tumor metastasis. At low concentrations, MLL induced anti-metastatic effects on MCF-7-SC by inhibiting the EMT process. Exposure to MLL also led to an increase in the epithelial marker E-cadherin, but decreased protein levels of the mesenchymal markers Snail and Slug. Collectively, this study provides evidence that lemon leaves possess cytotoxicity and anti-metastatic properties. Therefore, MLL may prove to be beneficial as a medicinal plant for alternative novel anticancer drugs and nutraceutical products.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.9
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• pp.5017-5021
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• 2013

Objective: MicroRNAs (miRNAs) are a small class of non-coding, single-stranded RNAs with a critical role in genesis and maintenance of renal cancer mainly through binding to 3'-untranslated regions (3'UTR) of target mRNAs, which causes a block of translation and/or mRNA degradation. The aim of the present study was to investigate the potential effects of miR-122 in human renal cell carcinomas. Methods: The expression level of miR-122 was quantified by qRT-PCR. MTT, colony formation, invasion and migration assays were used to explore the potential functions of miR-122 in human renal cell carcinoma cells. Results: Cellular growth, invasion and migration in two A498 and 786-O cells were significantly increased after miR-122 transfection. Further experiments demonstrated that overexpression of miR-122 resulted in the increase of phospho-Akt (Ser473) and phospho-mTOR (Ser2448), then activation of mTOR targets, p70S6K and 4E-BP1. Conclusions: The up-regulation of miR-122 may play an important role in the progress of renal cancer through activating PI3K/Akt signal pathway and could be a potential molecular target for anti-cancer therapeutics.

• Journal of Ginseng Research
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• v.42 no.1
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• pp.116-121
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• 2018

Background: Black ginseng (BG) has greatly enhanced pharmacological activities relative to white or red ginseng. However, the effect and molecular mechanism of BG on muscle growth has not yet been examined. In this study, we investigated whether BG could regulate myoblast differentiation and myotube hypertrophy. Methods: BG-treated C2C12 myoblasts were differentiated, followed by immunoblotting for myogenic regulators, immunostaining for a muscle marker, myosin heavy chain or immunoprecipitation analysis for myogenic transcription factors. Results: BG treatment of C2C12 cells resulted in the activation of Akt, thereby enhancing hetero-dimerization of MyoD and E proteins, which in turn promoted muscle-specific gene expression and myoblast differentiation. BG-treated myoblasts formed larger multinucleated myotubes with increased diameter and thickness, accompanied by enhanced Akt/mTOR/p70S6K activation. Furthermore, the BG treatment of human rhabdomyosarcoma cells restored myogenic differentiation. Conclusion: BG enhances myoblast differentiation and myotube hypertrophy by activating Akt/mTOR/p70S6k axis. Thus, our study demonstrates that BG has promising potential to treat or prevent muscle loss related to aging or other pathological conditions, such as diabetes.

• The Journal of Korean Medicine
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• v.38 no.2
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• pp.7-14
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• 2017

Objectives: This study evaluated the effect of aqueous extract from roots of Siberian ginseng on mTORC1 pathway. Methods: mTORC1 activity was measured by the phosphorylation status of p70 S6 kinase (S6K) in HeLa cells as well as the brain, liver and muscle tissues in diabetic db/db mice. Autophagy induction after the treatment of Siberian ginseng extract was evaluated by monitoring the conversion of cytoplasmic LC3I into lipidated LC3II in cultured human HeLa GFP-LC3 cells. Cell cycle analysis was performed in HeLa cells treated with Siberian ginseng using flow cytometry. Results: Among >2,800 plant products used for oriental medicine, Siberian ginseng was found to inhibit mTORC1 to phosphorylate S6 kinsase (S6K) in HeLa cells as well as the brain, liver and muscle tissues in diabetic db/db mice. Siberian ginseng-mediated mTORC1 activity was reversible unlike the prolonged suppression of mTORC1 by rapamycin when HeLa cells were grown in fresh media after the removal of the inhibitors. Siberian ginseng extract at concentrations to inhibit mTORC1 was not overly cytotoxic in cultured HeLa cells whereas rapamycin was obviously cytotoxic. The conversion of cytoplasmic LCI into lipidated LCII was increased by fivefold in HeLa GFP-LC3 cells treated with Siberian ginseng extract. Progression of cell cycle was attenuated at G2/M phase by the treatment of Siberian ginseng extract. Conclusions: These results suggest that the aqueous extract of Siberian ginseng possibly plays a good therapeutic role in various diseases involving mTORC1 signaling.

• 한국유가공학회:학술대회논문집
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• 1997.05a
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• pp.41-61
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• 1997

젖산균의 유전자 연구를 촉진하기 위해 간단하고 신속한 plasmid DNA의 분리방법과 electro-poration을 이용하여 vector plasmid의 간단하고 신속한 전이방법을 얻기 위해 젖산균의 형질전환에 영향하는 요인에 대하여 연구하였으며 연구결과는 다음과 같다. 1. O'Sullivan과 Klaenhammer의 방법을 개선하여 젖산균 plasmid DNA의 분리에 좋은 결과를 얻을 수 있는 신속하고 쉬운 방법을 고안하였으며, genomic DNA 분리에 이용되는 guanidium thio-cyanate 처리방법을 plasmid의 분리에 적용할 수 있었다. 2. L. casei, L. acidophilus. L. delbruekii var. bulgaricus. L. brevis와 L. plantarum 균주에서 plasmid를 확인하였으며, 돼지 분에서 분리된 L. lactis ssp. lactis. L. fermentum과 L. plantarum에서도 plasmid를 분리 확인하였다. 3. Lactococci의 plasmid분리는 lactobacilli와는 달리 mutanolysin의 처리없이도 잘 되었으며, L. lactis ssp. lactis와 Ent. faecalis에서 plasmid를 확인하였다. 4. E. coli plasimd 분리에 이용되는 MPS membrane filter 방법으로 젖산균 plasmid pLZ12의 분리가 가능하였으나, 세포파편이 filter를 막아 사용에 어려움이 있는 것으로 확인되었다. 5. Plasmid 분리없이 electroporation을 이용한 세포 대 세포 전이법으로 간편하고 빠르게 E. coli DH5${\alpha}$에 E. coli Jm109의 plasmid pBX19, pBR322를 전이시켰다. 6. L. lactis ssp. lactis 균주에 lysozyme 처리시 30${\sim}$80%의 생존율을 보였으며, 대부분의 L. acidophilus 균주의 경우 약 70%의 생존율을 보였다. L. casei 102S의 경우는 45분간 처리 시에도 100%의 생존율을 보였다. 8. L. lactis ssp. lactis 균주에 pLZ12를 6.0kV에서 전이시킨 결과 12.5kV에서보다 형질전환 효율이 훨씬 높았으며 lysozyme 처리에 의해 형질전환 효율이 증가되었다. 9. L. acidophilus 균주에 pLZ12를 전이시 6.0kV에서는 전이가 모두 이루어졌으나, 12.5kV에서는 L. acidophilus WIESBY와 NCFM에서 전이가 이루어지지 않았으며, lysozyme 처리 후 pLZ12를 전이시켰을 때 12kV보다 6.0kV에서 형질전환 효율이 증가되었다. 10. Gene Pulser와 Progenitor II를 사용하여 pLZ12를 L. lactis ssp. lactis 균주에 전이하였을 때 Gene Pulser에 비해 Progenitor II의 형질전환 효율이 현저히 떨어졌다. L. acidophilus HY7008과 HY7001은 두 기기 모두 형질전환이 이루어졌으나, L. acidophilus WEISBY와 NCFM은 Progeni-tor II에서 전이가 일어나지 않았으며, Gene Pulser에서 전이균주를 얻어 두 electroporator간에 형질전환 효율의 차이를 보였다. 11. L. casei 102S에 pLZ12를 electroporation시 낮은 전압에서 형질전환 효율이 비교적 좋았으며, 배양 시기를 달리하여 전이시켰을 때 대수생장 말기의 세포가 형질전환 효율이 좋았다. 12. L. casei 102S세포를 각각 10% glycerol, EB, 2차 증류수 등에 녹여 electroporation을 실시하였을 때 각각 $3.8{\times}10^3$, $5.0{\times}10^2$,1.5${\times}10^2$cfu의 형질전환 효율을 보였으며, 1.0mM HEPES, TE buffer를 사용하였을 때에는 전이가 이루어지지 않았다. 13. Plasmid pLZ12의 농도를 달리하여 electroporation을 하였을 때 형질전환 효율이 농도에 비례하여 증가하였다. 14. L. casei 102S에 대수생장 말기의 세포를 채취하여 10% glycerol, 200 Ohms, 25 ${\mu}$FD, 10kV/cm로 plasmid pLZ12를 electroporation할 때 최대 형질전환 효율인 3.8${\times}$10$^{3}$cfu를 얻었으며, lysozyme 처리가 다른 젖산균과는 달리 형질전환 효율을 증가시키지 못하였다. 15. L. casei 102S 세포를 10% glycerol과 EB에 녹여 -20$^{\circ}C$에서 냉동시킨 다음 1일과 7일 후의 세포를 electroporation한 결과 냉동시 세포에 손상을 주는 것으로 인식되었다.

• Nutrition Research and Practice
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• v.14 no.5
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• pp.478-489
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• 2020

BACKGROUND/OBJECTIVES: Morusin, a marker component of Morus alba L., possesses anti-cancer activity. The objective of this study was to determine autophagy-inducing effect of morusin in non-small cell lung cancer (NSCLC) cells and investigate the underlying mechanism. SUBJECTS/METHODS: Autophagy induction and the expression of autophagy-related proteins were analyzed by LC3 immunofluorescence and western blot, respectively. The role of autophagy and AMP-activated protein kinase (AMPK) was determined by treating NSCLC cells with bafilomycin A1, an autophagy inhibitor, and compound C, an AMPK inhibitor. Cytotoxicity and apoptosis induction were determined by MTT assay, trypan blue exclusion assay, annexin V-propidium iodide (PI) double staining assay, and cell cycle analysis. RESULTS: Morusin increased the formation of LC3 puncta in the cytoplasm and upregulated the expression of autophagy-related 5 (Atg5), Atg12, beclin-1, and LC3II in NSCLC cells, demonstrating that morusin could induce autophagy. Treatment with bafilomycin A1 markedly reduced cell viability but increased proportions of sub-G1 phase cells and annexin V-positive cells in H460 cells. These results indicate that morusin can trigger autophagy in NSCLC cells as a defense mechanism against morusin-induced apoptosis. Furthermore, we found that AMPK and its downstream acetyl-CoA carboxylase (ACC) were phosphorylated, while mammalian target of rapamycin (mTOR) and its downstream p70S6 kinase (p70S6K) were dephosphorylated by morusin. Morusin-induced apoptosis was significantly increased by treatment with compound C in H460 cells. These results suggest that morusin-induced AMPK activation could protect NSCLC cells from apoptosis probably by inducing autophagy. CONCLUSIONS: Our findings suggest that combination treatment with morusin and autophagy inhibitor or AMPK inhibitor might enhance the clinical efficacy of morusin for NSCLC.

• Biomolecules & Therapeutics
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• v.19 no.1
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• pp.21-26
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• 2011

Ceramide is an important lipid mediator of extracellular signals that control various cellular functions, including apoptosis. In this study, we showed that ceramide induced apoptosis in U373MG human glioblastoma cells associated with G1 cell cycle arrest. Treatment of cells with ceramide increased proapoptotic Bax expression and inhibited the expression of antiapoptotic Bcl-2 and Bcl-xL Ceramide also downregulated cyclin E, cyclin D1, cdk 2, and cdk4 which are involved in regulating cell cycle. In addition, ceramide suppressed phosphorylation of Akt, Bad, p70 S6 kinase, and 4E-BP1, suggesting the involvement of Akt/mTOR signaling pathway. Additionally, okadaic acid, an inhibitor of protein phosphatase 2A, partially blocked the ceramide mediated inhibition of phosphorylation of Akt and 4E-BP1. These results suggest that ceramide induces apoptosis in U373MG glioblastoma cells by regulating multiple signaling pathways that involve cell cycle arrest associated with Akt signaling pathway.

• Biomolecules & Therapeutics
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• v.29 no.6
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• pp.650-657
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• 2021

Metformin is an anti-diabetic drug and has anticancer effects on various cancers. Several studies have suggested that metformin reduces cell proliferation and stimulates cell-cycle arrest and apoptosis. However, the definitive molecular mechanism of metformin in the pathophysiological signaling in endometrial tumorigenesis and metastasis is not clearly understood. In this study, we examined the effects of metformin on the cell viability and apoptosis of human cervical HeLa and endometrial HEC-1-A and KLE cancer cells. Metformin suppressed cell growth in a dose-dependent manner and dramatically evoked apoptosis in HeLa cervical cancer cells, while apoptotic cell death and growth inhibition were not observed in endometrial (HEC-1-A, KLE) cell lines. Accordingly, the p27 and p21 promoter activities were enhanced while Bcl-2 and IL-6 activities were significantly reduced by metformin treatment. Metformin diminished the phosphorylation of mTOR, p70S6K and 4E-BP1 by accelerating adenosine monophosphate-activated kinase (AMPK) in HeLa cancer cells, but it did not affect other cell lines. To determine why the anti-proliferative effects are observed only in HeLa cells, we examined the expression level of liver kinase B1 (LKB1) since metformin and LKB1 share the same signalling system, and we found that the LKB1 gene is not expressed only in HeLa cancer cells. Consistently, the overexpression of LKB1 in HeLa cancer cells prevented metformin-triggered apoptosis while LKB1 knockdown significantly increased apoptosis in HEC-1-A and KLE cancer cells. Taken together, these findings indicate an underlying biological/physiological molecular function specifically for metformin-triggered apoptosis dependent on the presence of the LKB1 gene in tumorigenesis.