Mee-Young Ahn

Apicidin, a histone deaceylase inhibitor, induces both apoptosis and autophagy in human oral squamous carcinoma cells.

Apicidin acts as a potent histone deacetylases (HDAC) inhibitor and the precise mechanism for its anti-tumor activity in human oral squamous cell carcinoma (OSCC) cells has not been examined. The aim of this study was to evaluate the anti-tumor efficacy of apicidin through apoptosis and autophagy in OSCC cells. Cells were treated with apicidin and cell death was quantified. Cell cycle and apoptosis were measured using flow cytometry assay, immunoblot. Autophagy was characterized by the increase of LC3B-II and the formation of acidic vesicular organelles (AVOs). Apicidin significantly inhibited the proliferation of OSCC cells in a dose-dependent manner. Apicidin markedly up-regulated p21(WAF1) led to G2/M phase arrest. Apicidin significantly increased the number of apoptotic cells compared to untreated control. Apicidin induced not only apoptosis but also autophagy in OSCC cells. Apicidin dramatically increased the levels of LC3 type II expression, ATG5 protein expression and the accumulation of AVOs. Inhibition of autophagy enhanced apicidin-mediated cytotoxicity through an increase in apoptosis. These results suggest that apicidin exerts anti-tumor effects by inducing apoptosis and autophagy and provide novel evidence of apicidin-induced autophagy and autophagy inhibition enhances apicidin-mediated apoptosis in OSCC 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.

NOD1 and NOD2 stimulation triggers innate immune responses of human periodontal ligament cells

Nod-like receptors (NLRs) are cytosolic sensors for microbial molecules. Nucleotide-binding oligomerization domain (NOD)1 and NOD2 recognize the peptidoglycan derivatives, meso-diaminopimelic acid (meso-DAP) and muramyl dipeptide (MDP), respectively, and trigger host innate immune responses. In the present study, we examined the function of NOD1 and NOD2 on innate immune responses in human periodontal ligament (PDL) cells. The gene expression of NOD1 and NOD2 was examined by RT-PCR. IL-6 and IL-8 production in culture supernatants was measured by ELISA. Western blot analysis was performed to determine the activation of NF-κB and MAPK in response to Tri-DAP and MDP. The genes of NOD1 and NOD2 appeared to be expressed in PDL cells. Although the levels of NOD2 expression were weak in intact cells, MDP stimulation increased the gene expression of NOD2 in PDL cells. Tri-DAP and MDP led to the production of IL-6 and IL-8 and the activation of NF-κB and MAPK in PDL cells. Toll-like receptor (TLR) stimulation led to increased gene expression of NOD1 and NOD2 in PDL cells. Pam3CSK4 (a TLR2 agonist) and IFN-γ synergized with Tri-DAP and MDP to produce IL-8 and IL-6 in PDL cells. Our results indicate that NOD1 and NOD2 are functionally expressed in human PDL cells and can trigger innate immune responses.

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.

Intratumoral Photodynamic Therapy With Newly Synthesized Pheophorbide a in Murine Oral Cancer

Photodynamic therapy (PDT) is a therapeutic alternative for malignant tumors that uses a photosensitizer. Our group recently synthesized photosensitizer pheophorbide a (Pa) from chlorophyll-a. The present study investigated the therapeutic effect of PDT using intratumoral administration of the synthetic photosensitizer Pa in an in vivo murine oral squamous cell carcinoma (OSCC) animal model. Pa accumulation was measured using the fluorescence spectrum and imaging in living C3H mice. Intratumoral treatment of Pa-PDT (IT Pa-PDT) significantly inhibited the growth of transplanted OSCC cells. Histopathological examination of tumor tissues showed that PCNA expression was significantly decreased, while TUNEL-stained cells were markedly increased in the IT Pa-PDT group compared to controls. IT Pa-PDT-induced apoptosis was confirmed by immunoblot. Reduction of Bcl-2 and cleavage of caspase 3 and PARP were observed in IT Pa-PDT. These data demonstrate that IT Pa-PDT inhibited tumor cell proliferation and induced apoptosis, which is correlated with the anticancer activity of IT Pa-PDT. These potent antitumor activities of IT Pa-PDT were observed in both the immunohistochemistry and Western blot experiments. Our findings suggest the intratumoral therapeutic potential of Pa-PDT on OSCC. Additionally, demonstrated detection of Pa using a fluorescence spectroscopy system or molecular imaging system provides a means for simultaneous diagnosis and treatment of OSCC.

Histone deacetylase 8 as a novel therapeutic target in oral squamous cell carcinoma

The overexpression of histone deacetylases (HDACs) has been observed in many cancers and inhibition of specific HDAC has emerged as a new target for cancer therapy. The present study examined the expression of HDAC8 and the inhibitory effect of HDAC8 in oral squamous cell carcinoma (OSCC). The expression of HDAC8 was measured in human OSCC tissues and OSCC cell lines using immunohistochemistry and immunoblotting. HDAC8 was knocked down in OSCC cells by transfection with HDAC8 siRNAs and cell proliferation was quantified. Apoptosis and autophagy were measured using flow cytometry and immunoblotting. HDAC8 were overexpressed in OSCC tissues and OSCC cells, mainly localized in the cytoplasm. HDAC8 siRNAs effectively reduced the level of HDAC8 expression and HDAC8 silencing significantly inhibited the proliferation of OSCC cells. HDAC8 knockdown induced apoptotic cell death through caspases activation and pro-survival autophagy in OSCC cells. Combination with HDAC silencing and autophagy inhibition enhanced cell death by increasing apoptosis in OSCC cells. This study suggests that inhibition of HDAC8 might become a novel therapeutic strategy for OSCC.

Histone deacetylase 7 silencing induces apoptosis and autophagy in salivary mucoepidermoid carcinoma cells

BACKGROUND The overexpression of histone deacetylases (HDACs) has been observed in many cancers, and inhibition of specific HDACs has emerged as a new target for cancer therapy. We found that HDAC7 expression was selectively reduced by HDAC inhibitor apicidin in salivary mucoepidermoid carcinoma (MEC) cells. Here, we show that HDAC7 suppression has a potent antitumor effect in MEC cells. METHODS Histone deacetylases7 was knocked down using HDAC7 siRNAs, and cell proliferation was quantified. Cell cycle progression, apoptosis, and autophagy were measured by flow cytometry and immunoblotting. RESULTS Histone deacetylases 7 siRNAs inhibited cell proliferation and c-Myc expression, increased p27 expression, and caused G2/M phase cell cycle arrest in both YD-15 and Mc3 cells. HDAC7 silencing increased the sub-G1 population, Annexin V positive apoptotic cells and cleaved caspase3 levels. HDAC7 silencing induced an increase in autophagic markers, number of acidic vesicular organelles, and LC3B II levels, and decrease in p62 levels. HDAC7 siRNAs reduced the activation of ERK. HDAC7 knockdown resulted in growth inhibition through G2/M phase cell cycle arrest and induced both apoptosis and autophagy in MEC cells. CONCLUSIONS This study indicates that inhibition of HDAC7 might become a novel and effective therapeutic approach for treating to MEC.

Peripheral Ameloblastoma on the Retromolar Pad Area of the Mandible

Peripheral ameloblastoma, a rare and unusual variant of odontogenic tumor, representing 1% of all ameloblastomas. The extraosseous location is the peculiar feature of this type of tumor, which is otherwise similar to the classical ameloblastoma. This paper describes a case of peripheral ameloblastoma in a 43-year-old female affecting the left retromolar pad area of the mandible which was clinically diagnosed as a pyogenic granuloma. Histologically, the tumor showed of follicular ameloblastoma in continuity with a surface oral epithelium.