School of Radiation Medicine and Public Health, Medical College of Soochow University, Suzhou, China.
Carcinogenesis. 2011 Aug;32(8):1183-9. doi: 10.1093/carcin/bgr105. Epub 2011 Jun 10.
MicroRNAs (miRNAs), which regulate gene expression by partial complementarity to the 3' untranslated region of their target genes, have been implicated in cancer initiation and progression. However, the molecular mechanism underlying the regulation of miRNA expression during pancreatic tumorigenesis has not been extensively reported. In this study, we first compared the miRNA expression in human pancreatic cancers and adjacent normal tissues by miRNA array and identified 12 differentially expressed miRNAs. miR-132, which is downregulated in tumors, was further studied in greater detail. Decreased expression of miR-132 was confirmed in 16 of 20 pancreatic carcinomas (P < 0.0001), compared with their respective benign tissues by TaqMan miRNA assays. miR-132 expression was remarkably influenced by promoter methylation in PANC1 and SW1990 cells. Promoter hypermethylation was observed in tumor samples but not in the normal counterparts, and the expression of miR-132 negatively correlated with its methylation status (P = 0.013). miR-132 was transcribed by RNA polymerase II, and Sp1 played a major role in miR-132 transcription. The expression of Sp1 correlated with that of miR-132 in tissues. Moreover, cancerous tissues showed significantly lower Sp1-binding affinity to the miR-132 promoter, relative to non-tumor samples. Proliferation and colony formation of pancreatic cancer cells were suppressed in cells transfected with miR-132 mimics and enhanced in cells transfected with miR-132 inhibitor by negatively regulating the Akt-signaling pathway. Our present findings illustrate the mechanism driving miR-132 downregulation and the important role of miR-132 in pancreatic cancer development.
微小 RNA（miRNAs）通过与靶基因 3'非翻译区的部分互补来调节基因表达，已被牵涉到癌症的发生和进展中。然而，miRNA 表达在胰腺肿瘤发生过程中的调控的分子机制尚未得到广泛报道。在这项研究中，我们首先通过 miRNA 阵列比较了人胰腺癌细胞和相邻正常组织中的 miRNA 表达，鉴定出 12 个差异表达的 miRNA。miR-132 在肿瘤中下调，进一步进行了更详细的研究。TaqMan miRNA 分析显示，与相应的良性组织相比，在 20 例胰腺癌中的 16 例（P<0.0001）中，miR-132 的表达降低。miR-132 的表达在 PANC1 和 SW1990 细胞中受到启动子甲基化的显著影响。在肿瘤样本中观察到启动子超甲基化，但在正常对照中没有观察到，miR-132 的表达与甲基化状态呈负相关（P=0.013）。miR-132 由 RNA 聚合酶 II 转录，Sp1 在 miR-132 转录中起主要作用。Sp1 的表达与组织中的 miR-132 表达相关。此外，与非肿瘤样本相比，癌组织显示出对 miR-132 启动子的 Sp1 结合亲和力显著降低。转染 miR-132 模拟物的胰腺癌细胞的增殖和集落形成受到抑制，而转染 miR-132 抑制剂则通过负调控 Akt 信号通路增强。我们的研究结果说明了驱动 miR-132 下调的机制以及 miR-132 在胰腺癌发展中的重要作用。
