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Park S.A.,Catholic University of Pusan | Park Y.S.,Catholic University of Pusan | Bong S.M.,Biomolecular Function Research Branch | Lee K.S.,Catholic University of Pusan
Journal of Structural Biology | Year: 2016

Cholesterol-dependent cytolysins (CDCs) contribute to various pathogenesis by Gram-positive bacterial pathogens. Among them, pneumolysin (PLY) produced by Streptococcus pneumoniae is a major contributor to pneumococcal infections. Despite numerous studies of the cytolytic mechanism of PLY, little structural information on its interactions with a specific receptor of the cell membrane is available. We report here the first crystal structures of PLY in an apo-form and in a ternary complex with two mannoses at 2.8 Å and 2.5 Å resolutions, respectively. Both structures contained one monomer in an asymmetric unit and were comprised of four discontinuous domains, similar to CDC structures reported previously. The ternary complex structure showed that loop 3 and the undecapeptide region in domain 4 might contribute to cellular recognition by binding to mannose, as a component of a specific cell-surface receptor. Moreover, mutational studies and docking simulations for four residues (Leu431, Trp433, Thr459, and Leu460) in domain 4 indicated that Leu431 and Trp433 in the undecapeptide might be involved in the binding of cholesterol, together with the Thr459-Leu460 pair in loop 1. Our results provide structure-based molecular insights into the interaction of PLY with the target cell membrane, including the binding of mannose and cholesterol. © 2015 Elsevier Inc.

Choi D.H.,Hanyang University | Park S.J.,Center for Liver Cancer | Kim H.K.,Biomolecular Function Research Branch
Hepatobiliary and Pancreatic Diseases International | Year: 2015

Distinguishing ampullary carcinoma from pancreatic carcinoma is important because of their different prognoses. microRNAs are differentially expressed according to the tissue of origin. However, there is rare research on the differential diagnosis between the two types of cancers by microRNA in periampullary cancers. The present study was undertaken to compare microRNA profiles between ampullary and pancreatic carcinomas using microarrays. miR-215 was most significantly overexpressed in ampullary carcinomas; whereas the expressions of miR-134 and miR-214 were significantly lower in ampullary carcinomas than in pancreatic carcinomas. When these discriminatory microRNAs were applied to liver metastases, they were correctly predicted for the tissue of origin. Although this study is limited by small sample size, striking difference in microRNA expression and concordant expression of discriminating microRNAs in primary tumors and metastases suggest that these novel discriminatory microRNAs warrant future validation. © 2015, Hepatobiliary Pancreat Dis Int. All rights reserved.

Lee J.-H.,Seoul National University | Park J.-W.,Biomolecular Function Research Branch | Byun J.K.,Seoul National University | Kim H.K.,Biomolecular Function Research Branch | And 3 more authors.
Oncotarget | Year: 2015

Voltage-gated potassium (Kv) channels are known to be involved in cancer development and cancer cell proliferation. KV9.3, an electronically silent subunit, forms heterotetramers with KV2.1 in excitable cells and modulates its electrophysiological properties. However, the role of KV9.3 alone in non-excitable cancer cells has not been studied. Here, we evaluated the effect of silencing KV9.3 on cancer cell proliferation in HCT15 colon carcinoma cells and A549 lung adenocarcinoma cells. We confirmed the expression of KV9.3 mRNA in HCT15 and A549 cells and showed that silencing KV9.3 using small interfering RNA caused G0/G1 cell cycle arrest and alterations in cell cycle regulatory proteins in both HCT15 and A549 cells without affecting apoptosis. Also, stable knockdown of KV9.3 expression using short-hairpin RNA inhibited tumor growth in SCID mouse xenograft model. Using a bioinformatics approach, we identified Sp1 binding sites in the promoter region of the gene encoding KV9.3. We further found that Sp1 bound to this region and showed that the Sp1 inhibitor, mithramycin A, induced a concentration-dependent decrease in KV9.3 expression. Taken together, these data suggest that knockdown of KV9.3 inhibits proliferation in colon carcinoma and lung adenocarcinoma cell lines and may be regulated by Sp1.

Jeong K.-C.,Biomolecular Function Research Branch | Kim K.-T.,National Cancer Center | Seo H.-H.,National Cancer Center | Shin S.-P.,National Cancer Center | And 7 more authors.
Journal of Urology | Year: 2014

Purpose c-MYC is a promising target for cancer therapy but its use is restricted by unwanted, devastating side effects. We explored whether intravesical instillation of the c-MYC inhibitor KSI-3716 could suppress tumor growth in murine orthotopic bladder xenografts. Materials and Methods The small molecule KSI-3716, which blocks c-MYC/MAX binding to target gene promoters, was used as an intravesical chemotherapy agent. KSI-3716 action was assessed by electrophoretic mobility shift assay, chromatin immunoprecipitation, transcription reporter assay and quantitative reverse transcriptase-polymerase chain reaction. Inhibition of cell proliferation and its mechanism was monitored by cell cytotoxicity assay, EdU incorporation assay and flow cytometry. The in vivo efficacy of KSI-3716 was examined by noninvasive luminescence imaging and histological analysis after intravesical instillation of KSI-3716 in murine orthotopic bladder xenografts. Results KSI-3716 blocked c-MYC/MAX from forming a complex with target gene promoters. c-MYC mediated transcriptional activity was inhibited by KSI-3716 at concentrations as low as 1 μM. The expression of c-MYC target genes, such as cyclin D2, CDK4 and hTERT, was markedly decreased. KSI-3716 exerted cytotoxic effects on bladder cancer cells by inducing cell cycle arrest and apoptosis. Intravesical instillation of KSI-3716 at a dose of 5 mg/kg significantly suppressed tumor growth with minimal systemic toxicity. Conclusions The c-MYC inhibitor KSI-3716 could be developed as an effective intravesical chemotherapy agent for bladder cancer.

Park D.,National Cancer Center | Ahn K.-O.,Biomolecular Function Research Branch | Jeong K.-C.,Biomolecular Function Research Branch | Choi Y.,National Cancer Center
Nanotechnology | Year: 2016

Here, we fabricated polypyrrole nanoparticles (PPys) (termed HA10-PPy, HA20-PPy, and HA40-PPy) doped with different average molecular weight hyaluronic acids (HAs) (10, 20, and 40 kDa, respectively), and evaluated the effect of molecular weight of doped HA on photothermal induction, fluorescence quenching, and drug loading efficiencies. Doxorubicin-loaded HA-doped PPys (DOX@HA-PPys) could be used for imaging and therapy of triple-negative breast cancer (TNBC). Fluorescence turn-on, stimuli-responsive drug release, and photo-induced heating of DOX@HA-PPys enabled not only activatable fluorescence imaging but also subsequent chemo/photothermal dual therapy for TNBC. In particular, we illustrated the potential usefulness of the photothermal effect of the nanoparticles for overcoming chemoresistance in TNBC. © 2016 IOP Publishing Ltd.

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