Department of Pathology, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA.
Epigenetics. 2012 Aug;7(8):940-9. doi: 10.4161/epi.21236. Epub 2012 Jul 18.
The epigenetic regulation of genes has long been recognized as one of the causes of prostate cancer (PCa) development and progression. Recent studies have shown that a number of microRNAs (miRNAs) are also epigenetically regulated in different types of cancers including PCa. In this study, we found that the DNA sequence of the promoters of miR-29a and miR-1256 are partly methylated in PCa cells, which leads to their lower expression both in PCa cells and in human tumor tissues compared with normal epithelial cells and normal human prostate tissues. By real-time PCR, Western Blot analysis and miRNA mimic and 3'-UTR-Luc transfection, we found that TRIM68 is a direct target of miR-29a and miR-1256 and that the downregulation of miR-29a and miR-1256 in PCa cells leads to increased expression of TRIM68 and PGK-1 in PCa cells and in human tumor tissue specimens. Interestingly, we found that a natural agent, isoflavone, could demethylate the methylation sites in the promoter sequence of miR-29a and miR-1256, leading to the upregulation of miR-29a and miR-1256 expression. The increased levels of miR-29a and miR-1256 by isoflavone treatment resulted in decreased expression of TRIM68 and PGK-1, which is mechanistically linked with inhibition of PCa cell growth and invasion. The selective demethylation activity of isoflavone on miR-29a and miR-1256 leading to the suppression of TRIM68 and PGK-1 expression is an important biological effect of isoflavone, suggesting that isoflavone could be a useful non-toxic demethylating agent for the prevention of PCa development and progression.
基因的表观遗传调控一直被认为是前列腺癌（PCa）发展和进展的原因之一。最近的研究表明，许多 microRNAs（miRNAs）在不同类型的癌症中也受到表观遗传调控，包括 PCa。在这项研究中，我们发现 miR-29a 和 miR-1256 启动子的 DNA 序列在 PCa 细胞中部分甲基化，导致其在 PCa 细胞和人肿瘤组织中的表达低于正常上皮细胞和正常前列腺组织。通过实时 PCR、Western Blot 分析和 miRNA 模拟物和 3'-UTR-Luc 转染，我们发现 TRIM68 是 miR-29a 和 miR-1256 的直接靶标，并且 miR-29a 和 miR-1256 在 PCa 细胞中的下调导致 TRIM68 和 PGK-1 在 PCa 细胞和人肿瘤组织标本中的表达增加。有趣的是，我们发现一种天然化合物，异黄酮，可以使 miR-29a 和 miR-1256 启动子序列中的甲基化位点去甲基化，导致 miR-29a 和 miR-1256 的表达上调。异黄酮处理增加 miR-29a 和 miR-1256 的水平导致 TRIM68 和 PGK-1 的表达减少，这与抑制 PCa 细胞生长和侵袭有关。异黄酮对 miR-29a 和 miR-1256 的选择性去甲基化活性导致 TRIM68 和 PGK-1 表达的抑制是异黄酮的一个重要生物学效应，表明异黄酮可能是一种有用的无毒去甲基化剂，可用于预防 PCa 的发展和进展。
