Seong-Min Kwon

Amurensin G, a Potent Natural SIRT1 Inhibitor, Rescues Doxorubicin Responsiveness via Down-Regulation of Multidrug Resistance 1

The transition from a chemotherapy-responsive cancer to a chemotherapy-resistant one is accompanied by increased expression of multidrug resistance 1 (MDR1, p-glycoprotein), which plays an important role in the efflux from the target cell of many anticancer agents. We recently showed that a Forkhead box-containing protein of the O subfamily 1 (FoxO1) is a key regulator of MDR1 gene transcription. Because nuclear localization of FoxO1 is regulated by silent information regulator two ortholog 1 (SIRT1) deacetylase, we wondered whether SIRT1 dominates MDR1 gene expression in breast cancer cells. Overexpression of SIRT1 enhanced both FoxO reporter activity and nuclear levels of FoxO1. Protein expression of MDR1 and gene transcriptional activity were also up-regulated by SIRT1 overexpression. In addition, SIRT1 inhibition reduced both nuclear FoxO1 levels and MDR1 expression in doxorubicin-resistant breast cancer cells (MCF-7/ADR) cells. A potent SIRT1 inhibitor, amurensin G (from Vitis amurensis), was identified by screening plant extracts and bioassay-guided fractionation. The compound suppressed FoxO1 activity and MDR1 expression in MCF-7/ADR cells. Moreover, pretreatment of MCF-7/ADR cells with 1 μg/ml amurensin G for 24 h increased cellular uptake of doxorubicin and restored the responsiveness of MCF-7/ADR cells to doxorubicin. In xenograft studies, injection of 10 mg/kg i.p. amurensin G substantially restored the ability of doxorubicin to inhibit MCF-7/ADR-induced tumor growth. These results suggest that SIRT1 is a potential therapeutic target of MDR1-mediated chemoresistance and that it may be possible to develop amurensin G as a useful agent for chemoresistance reversal.

p-HPEA-EDA, a phenolic compound of virgin olive oil, activates AMP-activated protein kinase to inhibit carcinogenesis

Phenolic constituents of virgin olive oil are reported to have antitumor activity. However, the underlying molecular mechanisms and specific target proteins of virgin olive oil remain to be elucidated. Here, we report that dialdehydic form of decarboxymethyl ligstroside aglycone (p-HPEA-EDA), a phenolic compound of virgin olive oil, inhibits tumor promoter-induced cell transformation in JB6 Cl41 cells and suppress cyclooxygenase-2 (COX-2) and tumorigenicity by adenosine monophosphate-activated protein kinase (AMPK) activation in HT-29 cells. p-HPEA-EDA inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced phosphorylation of extracellular signal-regulated kinases 1/2 and p90RSK in JB6 Cl41 cells, resulting in the inhibition of cell proliferation, activator protein-1 transactivation and cell transformation promoted by TPA. Moreover, p-HPEA-EDA strongly inhibited the cell viability and COX-2 expression by activation of AMPK activity in HT-29 cells, resulted from depletion of intracellular adenosine triphosphate. p-HPEA-EDA-induced activation of caspase-3 and poly-adenosine diphosphate-ribose polymerase, phosphorylation of p53 (Ser15) and DNA fragmentation in HT-29 cells, leading to apoptosis. Importantly, p-HPEA-EDA suppressed the colony formation of HT-29 cells in soft agar. In contrast, Compound C, an AMPK inhibitor, and Z-DEVD-FMK, a caspase-3 inhibitor, blocked the p-HPEA-EDA-inhibited colony formation in HT-29 cells. In vivo chorioallantoic membrane assay also showed that p-HPEA-EDA-inhibited tumorigenicity of HT-29 cells. These findings revealed that targeted activation of AMPK and inhibition of COX-2 expression by p-HPEA-EDA contribute to the chemopreventive and chemotherapeutic potential of virgin olive oil against colon cancer cells.

Toll-like receptor 7 agonist, imiquimod, inhibits oral squamous carcinoma cells through apoptosis and necrosis.

BACKGROUND Toll-like receptor (TLR) agonists have anticancer effect by inducing apoptosis or activating immune cells. In this study, we investigated whether imiquimod, TLR7 agonist, inhibits the proliferation of oral cancer cells. METHODS Toll-like receptor 7 expression and IL-6/8 production by imiquimod were examined using RT-PCR and Enzyme-linked immunosorbent assay, respectively. Cell viability was examined by MTT assay. To examine apoptotic cell death, Annexin V/PI staining for flow cytometry and Western blot analysis were performed. Necrotic cell death was determined by leakage of lactate dehydrogenase (LDH), HMGB1, and PI staining in imiquimod-treated oral squamous cell carcinoma (OSCC) cells. RESULTS Toll-like receptor 7 mRNA was expressed in OSCC cells. Imiquimod induced IL-6 and IL-8 production in OSCC cells, suggesting the functional expression of TLR7. Imiquimod inhibited cells proliferation in a dose-dependent manner. The ratio of annexin V-positive cells and cleaved caspase-3/7 was increased by imiquimod treatment in OSCC cells, suggesting that imiquimod-induced cell death in OSCC cells may be owing to apoptosis. In addition, LDH secretion and PI staining were detected in OSCC cells treated with imiquimod, showing that imiquimod also induced necrotic cell death in the OSCC cells. CONCLUSIONS Imiquimod inhibited effectively the growth of OSCC cells by inducing apoptosis and necrosis.

Synthesized Pheophorbide a-mediated photodynamic therapy induced apoptosis and autophagy in human oral squamous carcinoma cells.

BACKGROUND Pheophorbide a (Pa) is a chlorine-based photosensitizer derived from an ethnopharmacological herb, and our group recently synthesized Pa by the removal of a magnesium ion and a phytyl group from chlorophyll-a. In this study, the effect of photodynamic therapy (PDT) with synthesized Pa was examined in a human oral squamous cell carcinoma (OSCC) cells. METHODS Cells were treated with PDT with Pa, and reactive oxygen species (ROS) and mitochondrial membrane potential [ΔΨ (m)] were examined. Apoptosis was measured using annexin V staining and immunoblot. Autophagy was characterized by the increase in LC3B-II and the formation of autophagosome and acidic vesicular organelles (AVOs). RESULTS Pa-PDT inhibited the proliferation of OSCC cells in a dose-dependent manner. Pa-PDT increased the number of apoptotic cells by inactivating ERK pathway. Pa-PDT also induced autophagy in OSCC cells evidenced by the increased levels of LC3 type II expression and the accumulation of AVOs. The inhibition of autophagy enhanced Pa-PDT-mediated cytotoxicity through an increase in necrosis. CONCLUSIONS These results suggest that synthesized Pa-PDT exerts anti-tumor effects by inducing apoptosis and autophagy and provide novel evidence that Pa-PDT induces autophagy, and autophagy inhibition enhances Pa-PDT-mediated necrosis in OSCC cells.

Transforming Growth Factor β1–Induced Heat Shock Protein 27 Activation Promotes Migration of Mouse Dental Papilla–derived MDPC-23 Cells

INTRODUCTION Transforming growth factor beta1 (TGFbeta1) regulates cellular functions including cell growth, differentiation, angiogenesis, migration, and metastasis. The TGFbeta1 signal transduction pathways are mostly undefined in mouse dental papilla-derived MDPC-23 cells. In this study, we investigated TGFbeta1-induced migration focusing on heat shock protein 27 (Hsp27) activation. METHODS Cellular responses mediated by TGFbeta1 in MDPC-23 cells were measured by Western blot and MTT assays. Cell migration was determined by counting migrated cells using the chemotaxis cell migration assay. RESULTS TGFbeta1 induced cell migration and increased the phosphorylation of Hsp27 and p38 MAPK in MDPC-23 cells. However, TGFbeta1 did not affect Akt/NF-kappaB signaling to regulate the migration of MDPC-23 cells. Inhibiting p38 MAPK with SB203580 blocked TGFbeta1-induced Hsp27 activation and cell migration. CONCLUSION Hsp27 phosphorylation followed by p38 MAPK activation was required for TGFbeta1-induced migration, and Hsp27 itself contributed to MDPC-23 cell migration.

Pheophorbide a-mediated photodynamic therapy induces apoptotic cell death in murine oral squamous cell carcinoma in vitro and in vivo

Photodynamic therapy (PDT) with several photosensitizers is a promising modality for the treatment of cancer. In this study, the therapeutic effect of PDT using the synthetic photosensitizer pheophorbide a (Pa-PDT) was examined in AT-84 murine oral squamous cell carcinoma (OSCC) cells. The MTT assay revealed that Pa-PDT induced cell growth inhibition in a dose- and time-dependent manner. Pa-PDT treatment significantly induced intracellular ROS generation, which is critical for cell death induced by Pa-PDT. Cell cycle analysis showed the increased sub-G1 proportion of cells in Pa-PDT-treated cells. Induction of apoptotic cell death was confirmed by DAPI staining and the reduction of mitochondrial membrane potential (ΔΨm) on Pa-PDT-treated cells. The changes in apoptosis-related molecules were next examined using western blotting. Cytochrome c release and cleavage of caspase-3 and PAPR were observed in AT-84 cells, whereas Bcl-2 protein levels were decreased. To determine the therapeutic effect of Pa-PDT in vivo, a murine OSCC animal model was used. Treatment of mice with Pa-PDT significantly inhibited tumor growth, especially PDT with Pa intravenous administration (i.v. Pa-PDT), and increased proliferative cell nuclear antigen (PCNA) levels and TUNEL-stained apoptotic cells compared to vehicle-treated controls. The data demonstrate that the in vitro effects of Pa-PDT on the inhibition of tumor cell proliferation and induction of apoptosis correlate to the anticancer activity of Pa-PDT in vivo. Our findings suggest the therapeutic potential of Pa-PDT in OSCC.

Homeobox C5 expression is associated with the progression of 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis.

BACKGROUND Aberrant expression of homeobox genes (HOX), normally required for the differentiation of a particular tissue, has been reported in several types of cancer, but poorly addressed in oral squamous cell carcinoma (OSCC). The present study investigated the expression of HOXC5 in OSCC and identified molecular biomarker whose expression is associated with the multistep oral carcinogenesis. METHODS The expression of HOXC5, proliferation cell nuclear antigen (PCNA), and Bcl-2 was examined by RT-PCR and Western blot analysis and confirmed by immunohistochemistry and transferase-mediated dUTP nick end-labeling (TUNEL) assay in a 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue carcinogenesis model. RESULTS Homeobox genes C5 was overexpressed in SCC tissues, but not in normal tissues by RT-PCR and Western blot analysis. Along with the progress of multistep carcinogenesis, the levels of HOXC5 expression of mRNA and protein significantly increased during the dysplasia (moderate to severe dysplasia) when compared with normal and hyperplasia. The levels of PCNA and Bcl-2 were sequentially increased from hyperplasia to dysplasia and SCC. By immunohistochemistry, HOXC5 expression was significantly increased in dysplasia, whereas PCNA expression was gradually increased during tongue carcinogenesis. TUNEL-positive cells were increased until dysplasia, but reduced in SCC. CONCLUSIONS These results indicate that overexpression of HOXC5 is correlated with oral carcinogenesis and strongly contributed to the development of OSCC. HOXC5 may be a useful biomarker and has an emerging therapeutic target of OSCC.

Poly I:C inhibits cell proliferation and enhances the growth inhibitory effect of paclitaxel in oral sqaumous cell carcinoma

Abstract Objective. Toll-like receptors (TLR) signaling has dual effect of promoting tumor progression and anti-cancer property. This study was designed to determine the effect of polyinosinic-polycytidilic acid (poly I:C), a TLR3 agonist, on the proliferation of oral cancer cells. Materials and methods: Human oral squamous cell carcinoma cell lines, YD-10B and YD-8, were used. TLRs expression was examined by RT-PCR and IL-8 production by poly I:C was examined by ELISA. Cell proliferation was determined by MTT assay. Flow cytometry and Western blot analysis were performed to determine the molecular mechanism of poly I:C-induced cell death. Results. TLR3 was functionally expressed in YD-10B and YD-8 cells. Treatment of poly I:C inhibited the cell growth in a dose-dependent manner. Flow cytometry and Western blot analysis revealed that poly I:C induced apoptosis via a mitochondria-dependent pathway. In addition, combination treatment with poly I:C and paclitaxel more significantly inhibited cell proliferation compared with poly I:C or paclitaxel alone. Conclusions. Poly I:C effectively inhibits oral cancer cell proliferation and can be considered as a candidate to improve the inhibitory effect of anti-cancer drugs.

Lipopolysaccharide promotes adhesion and migration of murine dental papilla-derived MDPC-23 cells via TLR4.

Odontoblasts and/or dental pulp cells are responsible for tooth repair and dentin formation. Furthermore, adhesion and migration are critical processes for tissue regeneration. This study was performed to clarify whether lipopolysaccharide (LPS) modulates adhesion and migration of the murine odontoblast-like cell line MDPC-23, and whether Toll-like receptor 4 (TLR4) signaling is engaged in this process. TLR4 expression in MDPC-23 cells was examined by RT-PCR. Adhesion assay was performed using type I collagen-coated plates. Migration ability was determined by a commercial assay kit. Phosphorylation of IκB-α, FAK, AKT, and ERK was examined by Western blot analysis. TLR4 was functionally expressed in MDPC-23 cells. LPS treatment enhanced adhesion and migration of MDPC-23 cells in a dose-dependent manner. Blockade of TLR4 using its antibody restored LPS-induced adhesion and migration of MDPC-23 cells. These findings indicate that LPS, an immune activator from Gram-negative bacteria, can promote the adhesion and migration ability of MDPC-23 cells via TLR4.