Cancer Research-UK Labs and Department of Oncology, Imperial College London, School of Medicine, Hammersmith Hospital, Hammersmith Campus, London, United Kingdom.
Cancer Res. 2010 Jan 1;70(1):367-77. doi: 10.1158/0008-5472.CAN-09-1891. Epub 2009 Dec 22.
Endometrial cancer is the most common malignancy of the lower female reproductive tract. The tumor suppressor FOXO1 is downregulated in endometrial cancer compared with normal endometrium but the underlying mechanisms are not well understood. Using microRNA (miR) target prediction algorithms, we identified several miRs that potentially bind the 3'-untranslated region of FOXO1 transcripts. Expression profiling of normal and malignant endometrial samples by quantitative real-time PCR and Northern blot analysis revealed an inverse correlation between the levels of FOXO1 protein and the abundance of several of the in silico-predicted miRs, suggesting that loss of FOXO1 expression in endometrial cancer may be mediated by miRs. To determine the role of candidate miRs, we used the endometrial cancer cell lines HEC-1B and Ishikawa, which express FOXO1 at high and low levels, respectively. Expression of miR-9, miR-27, miR-96, miR-153, miR-182, miR-183, or miR-186, but not miR-29a, miR-128, miR-152, or miR-486 mimetics in HEC-1B cells was sufficient to significantly reduce the abundance of FOXO1. Conversely, FOXO1 expression was efficiently restored in the Ishikawa cell line upon simultaneous inhibition of miR-9, miR-27, miR-96, miR-153, miR-183, and miR-186. Moreover, induction of FOXO1 in Ishikawa cells by miR inhibitors was accompanied by G1 cell cycle arrest and cell death, and was attenuated by the small interfering RNA-mediated downregulation of FOXO1 expression. Our findings identify several miRs overexpressed in endometrial cancer that function in concert to repress FOXO1 expression. Further, aberrant miR expression results in deregulated cell cycle control and impaired apoptotic responses, and thus, may be central to endometrial tumorigenesis.
子宫内膜癌是女性生殖系统最常见的恶性肿瘤。与正常子宫内膜相比，肿瘤抑制因子 FOXO1 在子宫内膜癌中下调，但潜在机制尚不清楚。使用 microRNA (miR) 靶标预测算法，我们鉴定出了几种可能与 FOXO1 转录物 3'非翻译区结合的 miR。通过定量实时 PCR 和 Northern blot 分析对正常和恶性子宫内膜样本进行表达谱分析，揭示了 FOXO1 蛋白水平与几种计算机预测的 miR 丰度之间的负相关，表明子宫内膜癌中 FOXO1 表达的丧失可能由 miR 介导。为了确定候选 miR 的作用，我们使用了 HEC-1B 和 Ishikawa 两种子宫内膜癌细胞系，它们分别高水平和低水平表达 FOXO1。在 HEC-1B 细胞中表达 miR-9、miR-27、miR-96、miR-153、miR-182、miR-183 或 miR-186，但不是 miR-29a、miR-128、miR-152 或 miR-486 mimic，足以显著降低 FOXO1 的丰度。相反，在同时抑制 miR-9、miR-27、miR-96、miR-153、miR-183 和 miR-186 的情况下，FOXO1 的表达在 Ishikawa 细胞系中得到有效恢复。此外，miR 抑制剂诱导 Ishikawa 细胞中 FOXO1 的表达伴随着 G1 细胞周期停滞和细胞死亡，并且被 FOXO1 表达的小干扰 RNA 介导下调所减弱。我们的发现确定了几种在子宫内膜癌中过度表达的 miR，它们协同作用抑制 FOXO1 的表达。此外，异常的 miR 表达导致细胞周期控制失调和凋亡反应受损，因此可能是子宫内膜肿瘤发生的核心。
