Astudy on the mechanism of oral carcinoma progression upon the suppression of NF kB transcriptional activity by the nucleus-localization MALT1.

鳞状细胞癌是口腔最常见的恶性肿瘤，预后较差。然而，该疾病侵袭性行为的分子机制尚不清楚。我们之前发现粘膜相关淋巴组织1 （MALT1）在口腔癌中的表达频率不高。在本研究中，我们研究了MALT1表达缺失的机制及其对癌细胞表型改变的影响。通过亚硫酸修饰序列、甲基化特异性PCR和5-aza去甲基化处理，分析了MALT1基因启动子甲基化状态，该基因经常抑制各种肿瘤抑制基因的表达。转录起始位点- 256bp的特异性胞嘧啶发生甲基化，而其他胞嘧啶未发生甲基化，这种-256C甲基化导致MALT1表达缺失。为了了解MALT1失活对癌细胞表型的作用，我们使用野生型表达MALT1的癌细胞、显性阴性表达MALT1的癌细胞和MALT1基因特异性的siRNA，并进行了生物学检测；小鼠体外侵袭实验、3D胶原凝胶侵袭实验、明胶酶谱法、逃避实验、伤口愈合实验和肿瘤形成实验。外源表达野生型MALT1可降低小鼠的增殖和细胞外基质降解活性、迁移行为和肿瘤生长。然而，显性阴性MALT1的表达显著增强了这些细胞的活性。此外，转染抑制内源性和外源性野生型MALT1的抗MALT1 siRNA也增强了它们。综上所述，这些结果强烈提示MALT1特异性抑制口腔癌细胞的侵袭性特征，MALT1基因的表观遗传失活是导致口腔癌患者癌症进展和预后恶化的主要原因之一。

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.