Akihiko Miyawaki

Notch signaling induces EMT in OSCC cell lines in a hypoxic environment

Epithelial-mesenchymal transition (EMT) is an early step in the acquisition of invasiveness by malignant tumors. It has been clarified that the tumor microenvironment affects malignancy in a number of different carcinomas, in particular, that a hypoxic environment induces EMT. Activation of Notch signaling induces EMT, but it remains unclear how the Notch pathway is involved in oral squamous cell carcinoma (OSCC) under hypoxia. Three OSCC cell lines were cultured for examination under hypoxic (1% O2) and normoxic (21% O2) conditions. Expression of E-cadherin was investigated as a hallmark of EMT by immunohistochemical examination. Cell motility and invasion were examined by wound-healing and invasion assays, respectively. The expression of Notch pathway molecules was analyzed by qPCR. Hypoxia increased the mRNA expression of Notch receptors, ligands and target genes, and Snail. Hypoxia decreased the expression of E-cadherin, and increased the motility and invasiveness of OSCC cell lines. γ-secretase inhibitor, a Notch-specific inhibitor, prevented these effects caused by h-ypoxia. These findings suggest that hypoxia induces EMT in OSCC cell lines via activation of Notch signaling, and inhibition of the Notch signaling pathway to suppress EMT may be a useful approach for the treatment of OSCC.

The transcription factor Snail enhanced the degradation of E-cadherin and desmoglein 2 in oral squamous cell carcinoma cells

Epithelial-mesenchymal transition (EMT), a key process in the tumor metastatic cascade, is characterized by the loss of cell-cell junctions and cell polarity as well as the acquisition of migratory and invasive properties. However, the precise molecular events that initiate this complex EMT process are poorly understood. Snail is a regulator of EMT that represses E-cadherin transcription through its interaction with proximal E-boxes in the promoter region of target genes. To investigate the role of Snail in EMT, we generated stable Snail transfectants using the oral squamous cell carcinoma cell line HSC-4 (Snail/HSC-4). Snail/HSC-4 cells had a spindle-shaped mesenchymal morphology, and enhanced migration and invasiveness relative to control cells. Consistent with these EMT changes, the downregulation of epithelial marker proteins, E-cadherin and desmoglein 2, and the upregulation of mesenchymal marker proteins, vimentin and N-cadherin were detected. Despite these observations, the mRNA levels of E-cadherin and desmoglein 2 did not decrease significantly. Although E-cadherin and desmoglein 2 proteins were stable in parental HSC-4 cells, these proteins were rapidly degraded in Snail/HSC-4 cells. The degradation of E-cadherin, but not desmoglein 2, was inhibited by dynasore, an inhibitor of dynamin-dependent endocytosis. Therefore, in HSC-4 cells Snail regulates levels of these proteins both transcriptionally and post-translationally.

Hyperosmotic stress up-regulates the expression of major vault protein in SW620 human colon cancer cells

The major vault protein (MVP) is the major constituent of the vault particle, the largest ribonuclear protein complex described to date and is identical to lung resistance-related protein (LRP). Although MVP is also expressed in several normal tissues, little is known about its physiological role. MVP played a protective role against some xenobiotics and other stresses. We thus investigated the effect of osmotic stress on MVP expression by treating human colon cancer SW620 cells with sucrose or NaCl. The expression level of both MVP protein and MVP mRNA was increased by the osmostress. Sucrose or sodium chloride could also enhance MVP promoter activity. Inhibition of p38 MAPK in SW620 cells by SB203580 inhibited the expression of MVP under hyperosmotic stress. These findings suggested that osmotic stress up-regulated the MVP expression through p38 MAPK pathway. Down-regulation of MVP expression by MVP interfering RNA (RNAi) in SW620 cells increased the sensitivity of the cells to hyperosmotic stress and enhanced apoptosis. Furthermore, MVP RNAi prevented the osmotic stress-induced, time-dependent increase in phosphorylated Akt. These findings suggest that the PI3K/Akt pathway might be implicated in the cytoprotective effect of MVP. Our data demonstrate that exposure of cells to hyperosmotic stress induces MVP that might play an important role in the protection of the cells from the adverse effects of osmotic stress.

A novel ameloblastoma cell line (AM-3) secretes MMP-9 in response to Wnt-3a and induces osteoclastogenesis

OBJECTIVE Ameloblastoma has a high risk of bone invasion and local recurrence. However, the mechanisms of bone invasion in ameloblastoma remain unclear. In this study, we established an experimental model for matrix metalloproteinase (MMP) induction and osteoclastogenesis using ameloblastoma-derived cells. STUDY DESIGN We established an ameloblastoma-derived cell line without viral genes and analyzed the expression of all Wnt and Frizzled members and MMPs by real-time reverse transcription-polymerase chain reaction, and analyzed the activity of MMP-2 and MMP-9 by the in-gel-gelatinase assay. RESULTS AM-3, newly established ameloblastoma-derived cells retained the morphology of primary-cultured ameloblastoma cells. AM-3 cells overexpressed the messenger RNA of Wnt-5a, Frizzled-2, MMP-2, and MMP-9 and showed the potential of osteoclastogenesis. In addition, Wnt-3a-treatment induced expression and activation of MMP-9 in AM-3 cells. CONCLUSIONS Our study suggests that AM-3 cells retained the characteristics of ameloblastoma, without acquiring typical features of cancer cells. Furthermore, Wnt signaling induced MMP-9 in ameloblastoma cells.

Immortalization and characterization of normal oral epithelial cells without using HPV and SV40 genes

a b s t r a c t Background: As oral neoplasm often originates from epithelium, an immortalized epithelial cell line could be useful for the research of oral carcinogenesis. Although several oral epithelial cell lines were reported, they were either derived from cancer or immortalized by human papilloma virus or simian virus 40 genes, which have the potential to induce carcinogenesis. Materials and methods: We established two immortalized cell lines from human oral epithelium by transducing mutant cyclin dependent kinase 4, cyclin D1, and human telomerase reverse transcrip- tase with or without dominant-negative p53 into primary-cultured normal oral gingival epithelial cells using recombinant lentivirus vectors and named them MOE (mouth-ordinary-epithelium) 1a and MOE1b, respectively. Results: MOE1 cells could be passaged for nine months or more, and the morphology of the cells did not change in comparison with that of fresh primary-cultured epithelial cells. MOE1 cells did not show epithelial-mesenchymal transition. MOE1b cells retain functional p53 and were considered to have less risk of genomic instabilities. Anchorage-independent growth was not observed in MOE1 cells. The expres- sions of cancer-associated genes including keratin-17 were not elevated in MOE1 cells, whereas oral cancer-derived HSC-2 cells showed overexpression of them. Furthermore, interleukin (IL)-1, IL-6, IL-8, tumor necrosis factor-, matrix metalloproteinase (MMP)-2, and MMP-9 were induced in response to lipopolysaccharide or heat-killed bacterium in MOE1 cells. Discussion: MOE1 cells kept the characteristics of normal epithelial cells without acquiring typical features of cancer cells and they could be useful not only for the study of oral neoplasm but also for other oral

A case of small cell carcinoma in the buccal region

Small cell carcinoma (SCC) in the head and neck region is an extremely rare high-grade malignant tumor. The authors report a case of an SCC occurring in the left buccal region. An 85-year-old man exhibited left cheek swelling that rapidly increased in size. Histopathological examination revealed invasive growth of an SCC into the musculo-adipose tissue. Immunohistochemically, the tumor cells were positive for cytokeratin (AE1/AE3), neuron-specific enolase (NSE) and CD56, but negative for cytokeratin 20. The patient received chemotherapy and radiotherapy, which resulted in marked regression of the tumor. Surgical resection was performed. The serum levels of NSE and pro-gastrin-releasing peptide (pro-GRP) increased and multiple metastases of the tumor occurred 1 month after surgery. SCCs tend to exhibit aggressive invasion and metastasis so chemotherapy for the whole body is recommended to prevent dissemination of the tumor cells. Serum levels of NSE and pro-GRP are considered to be useful tumor markers for understanding the status of the tumor and the clinical symptoms.

Treatment of Mandibular Fracture-Associated Infectious Pseudarthrosis Accompanied by Osteomyelitis in a Peritoneal Dialysis Patient

Peritoneal dialysis can be performed at home, and the transfer of solutes in the blood and other body fluids is slow compared to hemodialysis, reducing the load on the circulatory organs and lessening the frequency of hospital visits. We encountered a male patient in his 70s on peritoneal dialysis for end-stage renal failure who developed obsolete mandibular fracture-associated pseudarthrosis accompanied by osteomyelitis, which was treated with noninvasive reduction and fixation using circumferential wiring after the resolution of inflammation. The inflammation was resolved by an intravenous drip infusion of ampicillin and lavage of the local region through the fistulated region during hospitalization, and sequestrum was removed under local anesthesia. After the disappearance of drainage from the fistula, the mandibular fracture was fixed with circumferential wiring (noninvasive reduction and fixation) using a mandibular resin base (occlusion is possible). For noninvasive reduction and fixation of a midline fracture, a 6-week fixation period is usually necessary after surgery, but in this case it was fixed for 3 months after surgery because of the presence of infection and bone defect. In jaw bone infection in patients on long-term dialysis, high sensitivity to infection and incomplete cure occur due to a decline in cell-mediated immunity, renal osteodystrophy (ROD), and chronic kidney disease (CKD)-mineral and bone disorder. In the present patient, infection complicated the odontogenic source of infection and fracture, which may have protracted the condition. When jaw bone infection is noted in a patient on long-term dialysis, it is important to closely cooperate with the dialysis physician and select the administration method and dose corresponding to the route of administration and metabolism of antimicrobial agents in order to minimize the influence on the renal function. For the local region, infection control by oral hygiene management and cleaning is important, targeting treatment and management while avoiding the use of any antimicrobial agent.