DIVERSITY OF CANCER CELLS CAUSED BY CYTOSINE METHYLATION IN NON-CPG ISLAND

尽管CpG岛的整体甲基化导致基因沉默，但非CpG岛的特异性甲基化将在癌症进展过程中基因表达的多功能性和可塑性中发挥重要的表观遗传作用。我们在TrkA基因的5'-未翻译区发现了负顺式作用ap -1样序列TGAGCGA。稳态TrkA表达与ap -1样位点周围甲基化CpG的积累呈正相关。EMSA发现ap -1样位点主要由c-Jun同型二聚体结合；这种结合被sssi诱导的甲基化阻断。因此，甲基化激活TrkA基因表达是由c-Jun与负调节ap -1样位点结合的直接干扰引起的。此外，在伴有广泛神经周围浸润的晚期胰腺癌患者中，ap -1样位点周围的甲基化CpG随着TrkA表达的增加而积累。本文分析一例罕见的硬壁样纤维瘤病合并胸壁化生骨化。β -连环蛋白的积累与密码子41的体细胞激活突变有关。利用微解剖样品进行亚硫酸盐定位显示，BMP和激活素膜结合抑制剂（BAMBI）的表达在骨化灶处特异性下调，这是由于其基因启动子的超甲基化。由于BMP和经典的Wnt/ β -catenin/LEF1信号相互协同诱导间充质细胞向成骨细胞分化并促进骨形成，导致BMP信号响应性增强的表观遗传事件可能在化生骨的形成中起关键作用。我们在各种国际和国内会议上展示了我们的数据，并在学术期刊上发表了科学论文。

Although global methylation at CpG islands leads to gene silencing, specific methylation at non-CpG islands would play a crucial epigenetic role in the versatility and plasticity of gene expression during cancer progression. We demonstrated the negative cis-acting AP-1-like sequence TGAGCGA in the 5'-untranslated region of the TrkA gene. Steady-state TrkA expression correlated positively with the accumulation of methylated CpG around the AP-1-like site. By EMSA, the AP-1-like site was bound mainly by c-Jun homodimers; the binding was blocked by Sss I-induced methylation. Consequently, activation of TrkA gene expression by methylation was caused by the direct interference of c-Jun binding to the negatively regulating AP-1-like site. Furthermore, methylated CpG around the AP-1-like site was accumulated with increased TrkA expression in cases of advanced pancreatic cancer with extensive perineural invasion.A rare case of desmoid-type fibromatosis with metaplastic ossification in the chest wall is analyzed. Accumulation of beta-catenin associated with a somatic activating mutation in codon 41 was demonstrated. Bisulfite mapping using microdissected samples showed that BMP and activin membrane-bound inhibitor (BAMBI) expression was specifically downregulated at the ossifying focus due to hypermethylation of its gene promoter. Because both BMP and classical Wnt/beta-catenin/LEF1 signaling cooperatively and mutually induce differentiation of mesenchymal cells into osteoblastic cells and promote bone formation, the epigenetic event leading to the enhanced responsiveness to BMP signaling may play a crucial role in the formation of metaplastic bone.We have presented our data at various international as well as domestic meetings, and published scientific papers for academic journals.