Bhawal Ujjal Kumar, Tsukinoki Keiichi, Sasahira Tomonori, Sato Fuyuki, Mori Yusuke, Muto Noriko, Sugiyama Masaru, Kuniyasu Hiroki
Department of Oral Maxillofacial Diagnostic Science, Division of Pathology, Kanagawa Dental College, Yokosuka 238-8580, Japan.
Oncol Rep. 2007 Oct;18(4):817-24.
14-3-3 sigma has been a major G2/M checkpoint control gene and has demonstrated that its inactivation in various cancers occurs mostly by epigenetic hypermethylation, not by genetic change. This study investigated the methylation status and expression of the 14-3-3 sigma gene in 46 oral squamous cell carcinomas by methylation-specific polymerase chain reaction, reverse transcriptase-polymerase chain reaction, Western blotting and immunohistochemistry. Exons of the p53 gene were examined for mutations by sequencing analysis and CyclinD1 by immunohistochemistry. Methylation of the 14-3-3 sigma gene was detected in 13% (6/46) of the oral tumours, but not in corresponding adjacent non-malignant and normal gingival tissues. Intratumoural heterogeneity was found in the tumour tissues including three 14-3-3 sigma-methylated samples. Methylation of 14-3-3 sigma was detected in 3 SCC with p53 mutations and 3 with wild-type p53. Our major findings are: (a) methylation of 14-3-3 gene promoter is a rare event in oral cancer; (b) it is not always associated with 14-3-3 protein levels and there is no clear relationship between its methylation and p53 mutation; (c) loss of 14-3-3 sigma expression is associated with reduced CyclinD1 gene expression.
14-3-3σ一直是主要的G2/M期关卡控制基因，并且已经证明它在各种癌症中的失活大多是通过表观遗传高甲基化，而非基因改变。本研究通过甲基化特异性聚合酶链反应、逆转录聚合酶链反应、蛋白质免疫印迹法和免疫组织化学，调查了46例口腔鳞状细胞癌中14-3-3σ基因的甲基化状态和表达情况。通过测序分析检测p53基因的外显子是否存在突变，通过免疫组织化学检测细胞周期蛋白D1（CyclinD1）。在13%（6/46）的口腔肿瘤中检测到14-3-3σ基因的甲基化，但在相应的相邻非恶性组织和正常牙龈组织中未检测到。在肿瘤组织中发现了肿瘤内异质性，包括3个14-3-3σ甲基化样本。在3例p53突变的鳞状细胞癌和3例p53野生型的鳞状细胞癌中检测到14-3-3σ的甲基化。我们的主要发现是：（a）14-3-3基因启动子的甲基化在口腔癌中是罕见事件；（b）它并不总是与14-3-3蛋白水平相关，其甲基化与p53突变之间没有明确关系；（c）14-3-3σ表达缺失与细胞周期蛋白D1基因表达降低有关。
