Sung Un Kang

( )-Epigallocatechin-3-gallate (EGCG) inhibits HGF-induced invasion and metastasis in hypopharyngeal carcinoma cells

Hepatocyte growth factor (HGF) has recently attracted a considerable amount of attention as a stromal-derived mediator in tumor-stromal interactions, particularly because of its close involvement in cancer invasion and metastasis, and (-)-epigallocatechin-3-gallate (EGCG) can modulate the cell signaling associated with angiogenesis, metastasis, and migration of cancer cells. In the present study, we have investigated the effects of HGF on invasion and metastasis of hypopharyngeal carcinoma cells and the effect of EGCG on blocking HGF-induced invasion and metastasis in these cells. We found that HGF promoted the autophosphorylation of c-Met, HGF receptor, and that HGF-induced proliferation, colony dispersion, migration and invasion of tumors. We also observed that HGF enhanced the activity of matrix metalloproteinase (MMP)-9 and urokinase-type plasminogen activator (uPA) in hypopharyngeal carcinoma cells. In addition, HGF-induced the activation of Akt and Erk pathway as a downstreaming pathway of invasion. On the other hand, EGCG at physiologically relevant concentration (1 microM) suppressed HGF-induced tumor motility and MMP-9 and uPA activities, and the suppression of Akt and Erk pathway by EGCG was one of the downstream mechanisms to facilitate EGCG-induced anti-invasion effects. These results suggest that EGCG may serve as a therapeutic agent to inhibit HGF-induced invasion in hypopharyngeal carcinoma patients.

Non-Thermal Atmospheric Pressure Plasma Inhibits Thyroid Papillary Cancer Cell Invasion via Cytoskeletal Modulation, Altered MMP-2/-9/uPA Activity

Plasma, the fourth state of matter, is defined as a partially or completely ionized gas that includes a mixture of electrons and ions. Advances in plasma physics have made it possible to use non-thermal atmospheric pressure plasma (NTP) in cancer research. However, previous studies have focused mainly on apoptotic cancer cell death mediated by NTP as a potential cancer therapy. In this study, we investigated the effect of NTP on invasion or metastasis, as well as the mechanism by which plasma induces anti-migration and anti-invasion properties in human thyroid papillary cancer cell lines (BHP10-3 and TPC1). Wound healing, pull-down, and Transwell assays demonstrated that NTP reduced cell migration and invasion. In addition, NTP induced morphological changes and cytoskeletal rearrangements, as detected by scanning electron microscopy and immunocytochemistry. We also examined matrix metalloproteinase (MMP)-2/-9 and urokinase-type plasminogen activator (uPA) activity using gelatin zymography, uPA assays and RT-PCR. FAK, Src, and paxillin expression was detected using Western blot analyses and immunocytochemistry. NTP decreased FAK, Src, and paxillin expression as well as MMP/uPA activity. In conclusion, NTP inhibited the invasion and metastasis of BHP10-3 and TPC1 cells by decreasing MMP-2/-9 and uPA activities and rearranging the cytoskeleton, which is regulated by the FAK/Src complex. These findings suggest novel actions for NTP and may aid in the development of new therapeutic strategies for locally invasive and metastatic cancers.

Non-thermal atmospheric pressure plasma induces apoptosis in oral cavity squamous cell carcinoma: Involvement of DNA-damage-triggering sub-G1 arrest via the ATM/p53 pathway

Recent advances in physics have made possible the use of non-thermal atmospheric pressure plasma (NTP) in cancer research. Although increasing evidence suggests that NTP induces death of various cancer cell types, thus offering a promising alternative treatment, the mechanism of its therapeutic effect is little understood. In this study, we report for the first time that NTP led to apoptotic cell death in oral cavity squamous cell carcinoma (OSCC). Interestingly, NTP induced a sub-G(1) arrest in p53 wild-type OSCCs, but not in p53-mutated OSCCs. In addition, NTP increased the expression levels of ATM, p53 (Ser 15, 20 and 46), p21, and cyclin D1. A comet assay, Western blotting and immunocytochemistry of γH2AX suggested that NTP-induced apoptosis and sub-G(1) arrest were associated with DNA damage and the ATM/p53 signaling pathway in SCC25 cells. Moreover, ATM knockdown using siRNA attenuated the effect of NTP on cell death, sub-G(1) arrest and related signals. Taken together, these results indicate that NTP induced apoptotic cell death in p53 wild-type OSCCs through a novel mechanism involving DNA damage and triggering of sub-G(1) arrest via the ATM/p53 pathway. These findings show the therapeutic potential of NTP in OSCC.

Epicatechin protects auditory cells against cisplatin-induced death

Cisplatin, a chemotherapeutic drug that is widely used to treat various cancers, promotes ototoxicity at higher doses. In this study, the effect of epicatechin (EC) on cisplatin-induced hair cell death was investigated in a cochlear organ of Corti-derived cell line, HEI-OC1, and in vivo in zebrafish. Cisplatin promoted apoptosis and altered mitochondrial membrane potential (MMP) in HEI-OC1 cells. EC inhibited cisplatin-induced apoptosis and intracellular reactive oxygen species (ROS) generation. Labeling of zebrafish lateral line hair cells by the fluorescent dye YO-PRO1 was lost upon exposure to cisplatin, and EC protected against this cisplatin-induced loss of labeling in a dose-dependent manner. Scanning and transmission electron micrographs showed that treatment with EC protected against cisplatin-induced loss of kinocilium and stereocilia in zebrafish neuromasts. These results suggest that EC prevents cisplatin-induced ototoxicity by blocking ROS generation and by preventing changes in MMP.

Green tea (−)-epigallocatechin-3-gallate inhibits HGF-induced progression in oral cavity cancer through suppression of HGF/c-Met☆

Hepatocyte growth factor (HGF) and c-Met have recently attracted a great deal of attention as prognostic indicators of patient outcome, and they are important in the control of tumor growth and invasion. Epigallocatechin-3-gallate (EGCG) has been shown to modulate multiple signal pathways in a manner that controls the unwanted proliferation and invasion of cells, thereby imparting cancer chemopreventive and therapeutic effects. In this study, we investigated the effects of EGCG in inhibiting HGF-induced tumor growth and invasion of oral cancer in vitro and in vivo. We examined the effects of EGCG on HGF-induced cell proliferation, migration, invasion, induction of apoptosis and modulation of HGF/c-Met signaling pathway in the KB oral cancer cell line. We investigated the antitumor effect and inhibition of c-Met expression by EGCG in a syngeneic mouse model (C3H/HeJ mice, SCC VII/SF cell line). HGF promoted cell proliferation, migration, invasion and induction of MMP (matrix metalloproteinase)-2 and MMP-9 in KB cells. EGCG significantly inhibited HGF-induced phosphorylation of Met and cell growth, invasion and expression of MMP-2 and MMP-9. EGCG blocked HGF-induced phosphorylation of c-Met and that of the downstream kinases AKT and ERK, and inhibition of p-AKT and p-ERK by EGCG was associated with marked increases in the phosphorylation of p38, JNK, cleaved caspase-3 and poly-ADP-ribose polymerase. In C3H/HeJ syngeneic mice, as an in vivo model, tumor growth was suppressed and apoptosis was increased by EGCG. Our results suggest that EGCG may be a potential therapeutic agent to inhibit HGF-induced tumor growth and invasion in oral cancer.

Tolfenamic acid induces apoptosis and growth inhibition in head and neck cancer: involvement of NAG-1 expression

Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) is induced by nonsteroidal anti-inflammatory drugs and possesses proapoptotic and antitumorigenic activities. Although tolfenamic acid (TA) induces apoptosis in head and neck cancer cells, the relationship between NAG-1 and TA has not been determined. This study investigated the induction of apoptosis in head and neck cancer cells treated by TA and the role of NAG-1 expression in this induction. TA reduced head and neck cancer cell viability in a dose-dependent manner and induced apoptosis. The induced apoptosis was coincident with the expression of NAG-1. Overexpression of NAG-1 enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. TA significantly inhibited tumor formation as assessed by xenograft models, and this result accompanied the induction of apoptotic cells and NAG-1 expression in tumor tissue samples. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression in head and neck squamous cell carcinoma, providing an additional mechanistic explanation for the apoptotic activity of TA.

Expression of NSAID-activated gene-1 by EGCG in head and neck cancer: involvement of ATM-dependent p53 expression.

Epigallocatechin-3-gallate (EGCG), a major polyphenolic constituent of green tea, possesses remarkable chemopreventive and therapeutic potential against various types of cancer, including head and neck squamous cell carcinoma (HNSCC). However, the molecular mechanism involved is not completely understood. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a transforming growth factor β superfamily protein, is shown to be induced by several antitumorigenic compounds and to exhibit proapoptotic and antitumorigenic activities. In this report, we demonstrate that EGCG transcriptionally induced the expression of NAG-1 during EGCG-induced apoptosis of HNSCC cells. Reporter assays, using the luciferase constructs containing the NAG-1 promoter, demonstrate that p53 is required for EGCG-mediated activation of NAG-1. Overexpression of NAG-1 enhanced the apoptotic effect of EGCG, whereas suppression of NAG-1 expression by small interfering RNA attenuated EGCG-induced apoptosis in HNSCC cells. Subsequently, we found that ataxia-telangiectasia mutated (ATM) plays an important role in activating these proapoptotic proteins (NAG-1 and p53) and cell cycle inhibitor (p21). Furthermore, EGCG significantly inhibited tumor formation as assessed by xenograft models, and this result is accompanied with induction of apoptotic cells and NAG-1 expression in tumor tissue samples. Taken together, these results demonstrate for the first time that EGCG induces apoptosis via ATM/p53-dependent NAG-1 expression in HNSCC, providing an additional mechanistic explanation for the apoptotic activity of EGCG.

Epicatechin inhibits radiation-induced auditory cell death by suppression of reactive oxygen species generation.

Radiation-induced toxicity limits the delivery of high-dose radiation to head and neck lesions. The aim of this study was to investigate the effectiveness of epicatechin (EC), a minor component of green tea extract, on radiation-induced ototoxicity in vitro and in vivo. The effect of EC on radiation-induced cytotoxicity was analyzed in the organ of Corti-derived cell lines, HEI-OC1 and UB-OC1. The cell viability, apoptosis, reactive oxygen species generation, and mitochondrial membrane potential as well as changes in the signal pathway related to apoptosis were investigated. Then, the therapeutic effects of hearing protection and drug toxicity of EC were explored in a zebrafish and rat model. Radiation-induced apoptosis and altered mitochondrial membrane potential in HEI-OC1 and UB-OC1 were observed. EC inhibited radiation-induced apoptosis and intracellular reactive oxygen species generation. EC markedly attenuated the radiation-induced embryotoxicity and protected against radiation-induced loss and changes of auditory neuromast in the zebrafish. In addition, intratympanic administration of EC was protective against radiation-induced hearing loss in the rat model, as determined by click-evoked auditory brainstem (P<0.01). EC significantly reduced the expression of p-JNK, p-ERK cleaved caspase-3, and cleaved PARP compared to their significant increase after radiation treatment. The results of this study suggest that EC significantly inhibited radiation-induced apoptosis in auditory hair cells and may be a safe and effective candidate treatment for the prevention of radiation-induced ototoxicity.

Imiquimod induces apoptosis of human melanocytes.

Development of vitiligo-like hypopigmentary lesions associated with topical imiquimod has been reported. We hypothesized that mode of action of imiquimod in melanocytes may include triggering of apoptosis resulted in loss of cells, which may be a possible mechanism of imiquimod-induced hypopigmentary lesions. Therefore, we investigated whether imiquimod induces apoptosis of human melanocytes and also whether it modulates expression of apoptosis-related molecules in human melanocytes. Imiquimod treatment induced apoptosis of melanocytes, which was observed by TUNEL assay and Hoechst 33258 staining. Imiquimod-induced apoptosis was further shown by measuring mitochondrial membrane potential in melanocytes. The apoptotic activity of imiquimod was associated with caspase-3, Bcl-2 and mitogen-activated protein kinase expression in melanocytes. These results indicated that imiquimod induces apoptosis of melanocytes. These findings may provide a clue to understand pathogenesis of imiquimod-induced vitiligo-like hypopigmentary lesions.

Inhibition of p38 mitogen-activated protein kinase ameliorates radiation-induced ototoxicity in zebrafish and cochlea-derived cell lines.

Radiation is a widely used treatment for head and neck cancers, and one of its most severe side effects is ototoxicity. Radiation-induced ototoxicity has been demonstrated to be linked to the increased production of ROS and MAPK. We intended to investigate the effect of p38 inhibition on radiation-induced ototoxicity in cochlea-derived HEI-OC1 cells and in a zebrafish model. The otoprotective effect of p38 inhibition against radiation was tested in vitro in the organ of Corti-derived cell line, HEI-OC1, and in vivo in a zebrafish model. Radiation-induced apoptosis, mitochondrial dysfunction, and an increase of intracellular NO generation were demonstrated in HEI-OC1 cells. The p38-specific inhibitor, SB203580, ameliorated radiation-induced apoptosis and mitochondrial injury in HEI-OC1 cells. p38 inhibition reduced radiation-induced activation of JNK, p38, cytochrome c, and cleavage of caspase-3 and PARP in HEI-OC1 cells. Scanning electron micrography showed that SB203580 prevented radiation-induced destruction of kinocilium and stereocilia in zebrafish neuromasts. The results of this study suggest that p38 plays an important role in mediating radiation-induced ototoxicity and inhibition of p38 could be a plausible option for preventing radiation ototoxicity.