| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Squamous cell carcinoma is a most frequent malignant neoplasm in the oral cavity with worse prognosis. However, a molecular mechanism(s) responsible for aggressive behaviors of the disease remains unknown. We previously found that mucosa-associated lymphoid tissue 1 (MALT1) is not expressed in oral carcinomas in a high frequency. In the present study, we examined the mechanism(s) of loss of the MALT1 expression and its effects on phenotypic alterations of carcinoma cells.
Promoter methylation status of MALT1 gene, which frequently suppresses various tumor suppressor gene expression, was analyzed by bisulfite-modified sequence, methylation-specific PCR and demethylation treatment by 5-aza. Specific cytosine at -256 bp but not other cytosines from the transcription start site was methylated, and this -256C methylation was responsible for loss of the MALT1 expression. To understand a role of MALT1 inactivation on carcinoma cell phenotypes, we used wild-type MALT1-expressing carcinoma cells, dominant-negative MALT1-expressing carcinoma cells and siRNA specific to MALT1 gene, and performed biological assays ; in vitro invasion assay, 3D collagen gel invasion assay, gelatin zymography, evasion assay, wound healing assay and tumor formation assay in mice. Exogenous expression of wild-type MALT1 reduced proliferation and extracellular matrix-degrading activities, migratory behavior and tumor growth in mice. However, expression of dominant-negative MALT1 dramatically enhanced these cellular activities. In addition, transfection of anti-MALT1 siRNA, which blocks endogenous and exogenous wild-type MALT1, also enhanced them. Altogether, these results strongly suggest that MALT1 specifically suppresses aggressive features of oral carcinoma cells and that epigenetic inactivation of MALT1 gene is one of major causative resulting in carcinoma progression and worse prognosis of patients suffering from the disease.
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