Department of Surgery, Kyushu University Beppu Hospital, 4546 Tsurumihara, Beppu 874-0838, Japan.
Carcinogenesis. 2012 Dec;33(12):2391-7. doi: 10.1093/carcin/bgs288. Epub 2012 Sep 15.
The mammalian target of rapamycin (mTOR) is a downstream integrator of essential pathways. mTOR signaling is frequently dysregulated in a variety of human cancers, and in silico analysis has revealed two miR-144 binding sites in the mTOR 3' untranslated region. We investigated the clinicopathologic magnitude of the mTOR pathway regulating microRNA, miR-144 in colorectal cancer (CRC) cases. The regulation of mTOR by miR-144 was examined with inhibitor miR-144-transfected cells. We also investigated changes in sensitivity to the mTOR inhibitor, rapamycin, in inhibitor miR-144-transfected cells. Quantitative RT-PCR was used to evaluate the clinicopathologic significance of miR-144 expression in 137 CRC. Furthermore, we assessed the correlation between CRC prognosis and the expression of 16 genes in the Akt/mTOR pathway. In vitro assays showed that mTOR is a direct target of miR-144, and downregulation of miR-144 facilitated proliferation of CRC cell line, HT29. In addition, the viability of HT29 cells with downregulated miR-144 expression was significantly reduced with rapamycin treatment. Low expression levels of miR-144 were associated with enhanced malignant potential such as venous invasion (P = 0.0013), liver metastasis (P = 0.08), liver recurrence (P = 0.0058) and poor prognosis (P = 0.0041). Multivariate analysis indicated that low miR-144 expression was an independent prognostic factor for survival. Among many genes consisting of the mTOR pathway, only high expression of Rictor was associated with poor prognosis of CRC. miR-144 is a meaningful prognostic marker. Downregulation of miR-144 leads to poor prognosis of CRC patients via activation of the mTOR signaling pathway.
哺乳动物雷帕霉素靶蛋白（mTOR）是下游整合的重要途径。 mTOR 信号在各种人类癌症中经常失调，计算机分析已经揭示了 mTOR 3'非翻译区中的两个 miR-144 结合位点。我们研究了大肠癌（CRC）病例中调节 microRNA，miR-144 的 mTOR 途径的临床病理幅度。通过转染抑制剂 miR-144 的细胞来检查 mTOR 受 miR-144 的调节。我们还研究了转染抑制剂 miR-144 的细胞对 mTOR 抑制剂雷帕霉素的敏感性变化。定量 RT-PCR 用于评估 137 例 CRC 中 miR-144 表达的临床病理意义。此外，我们评估了 Akt/mTOR 途径中 16 个基因的表达与 CRC 预后之间的相关性。体外试验表明，mTOR 是 miR-144 的直接靶标，下调 miR-144 促进了 CRC 细胞系 HT29 的增殖。此外，下调 miR-144 表达的 HT29 细胞的活力在用雷帕霉素处理时显着降低。 miR-144 表达水平低与增强的恶性潜能相关，如静脉侵犯（P = 0.0013），肝转移（P = 0.08），肝复发（P = 0.0058）和预后不良（P = 0.0041）。多变量分析表明，miR-144 低表达是生存的独立预后因素。在构成 mTOR 途径的许多基因中，只有 Rictor 的高表达与 CRC 的预后不良相关。 miR-144 是一个有意义的预后标志物。下调 miR-144 通过激活 mTOR 信号通路导致 CRC 患者预后不良。
