组蛋白乙酰化和甲基化修饰调控整合素β6信号在口腔白斑恶性转化中的作用机制

Oral leukoplakia (OL) is the　most common oral potentially malignant lesion. Malignant transformation of oral leukoplakia is severely threatening the health　of human being. Compelling evidences have demonstrated that the overexpression of Integrin αvβ6 signalling contributes to the malignant transformation of oral leukoplakia. However, the regulation mechanism of αvβ6 overexpression during the malignant transformation of OL remains unknown. With the support of our previous project of National Science Foundation of China, we found that the high gene transcriptional level is the main cause of overexpression of integrin β6 –the key subunit of integrin αvβ6 involved in the enhanced transcriptional signal of avb6 in human oral squamous cell carcinoma. Meanwhile, we have also demonstrated that hyper-acetylation of histones H3 and H4 and increased binding of H3K4Me3 at ITGB6 promoter are involved in the upregulated expression of ITGB6 in human oral squamous cell carcinoma cells. Since oral leukoplakia malignant transformation will result in the development of oral squamous cell carcinoma, we therefore hypothesize that aberrant histone acetylation and methylation is responsible for the overexpression of the ITGB6 signal during the process of oral leukoplakia malignant transformation, leading to the development of oral squamous cell carcinoma. To test this hypothesis, oral leukoplakia cells , oral squamous cell carcinoma cells, human oral leukoplakia and oral squamous cell carcinoma specimens ,and animal model of oral leukoplakia malignant transformation will be employed to investigate the role of histone acetylation, histone methylaton and their crosstalk in the regulation of enhanced transcriptional signal of ITGB6 during the process of oral leukoplakia malignant transformation, and to identify the key molecules that trigger and guide this process. We will further investigate the effect of blocking the ITGB6 signal mediated by histone acetylation and methylation in the process of oral leukoplakia malignant transformation by using gene knock out mice. This project will offer better understanding of the molecular mechanisms of oral leukoplakia malignant transformation underlying this epigenetic regulation, and identification of key molecules in these changes may prove highly beneficial for the therapeutic strategies aiming to inhibit key genes activated by epigenetic upregulation in oral leukoplakia malignant transformation.

口腔白斑是典型的口腔鳞癌癌前病变，严重威胁人类健康。整合素αvβ6高表达参与口腔白斑恶性转化的发生发展，但具体调控机制未知。在前一基金资助下，我们发现αvβ6在口腔鳞癌中高表达是由其关键性亚单位整合素β6（ITGB6 ）高转录造成；与ITGB6启动子区结合的乙酰化组蛋白和组蛋白甲基化标志H3K4me3参与口腔鳞癌ITGB6过度转录。由于白斑恶性转化结果为口腔鳞癌，我们推测组蛋白乙酰化和甲基化修饰异常参与调控白斑恶性转化时ITGB6过度转录，导致口腔鳞癌发生。本项目拟用人口腔白斑及鳞癌细胞、组织标本及白斑恶性转化动物模型探讨组蛋白乙酰化和甲基化修饰及相互作用对白斑恶性转化时ITGB6过度转录的影响，并用基因敲除鼠动物模型探讨阻断组蛋白乙酰化和甲基化修饰介导的ITGB6信号对白斑恶性转化进程的影响。该研究有望从表观遗传调控角度完善白斑恶性转化机制，为寻找新的有效的白斑恶性转化干预靶点奠定基础。

口腔黏膜白斑是一种公认且常见的癌前病变，癌变率在10-30%之间，其癌变是一个多基因多步骤参与过程。由于癌变机制不甚明了，迄今为止，对于白斑癌变仍缺乏特效的防治措施。整合素β6高表达参与口腔白斑恶性转化的发生发展，但具体调控机制未知。本项目利用人口腔白斑及鳞癌细胞、组织标本及白斑恶性转化动物模型首次发现口腔白斑恶性转化时转录因子SRF和JunB的表达逐渐升高，高表达SRF和JunB的促进口腔白斑细胞迁移及浸润能力，并且参与ITGB6的过度转录；同时发现转录因子JunB与乙酰化酶（HAT）CBP介导的乙酰化参与TGF-β1诱导的ITGB6转录调控；活化的G蛋白偶联受体LPA1与Gi蛋白偶联，介导转录因子SMAD3和ETS-1与整合素β6启动子结合，参与上调ITGB6的转录表达；发现染色质重塑酶Brg1在口腔鳞癌中的高表达并参与口腔鳞癌细胞的侵袭转移，但并不参与调控整合素β6的转录表达。本项目的研究结果不仅为基因表达调控时转录因子和组蛋白修饰之间的相互作用通路提供新的直接证据，而且将从转录因子和组蛋白修饰相互作用通路的新角度完善口腔白斑恶性转化的分子机制，寻找新的有效的口腔白斑恶性转化干预靶点奠定基础。