Department of General Surgery, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
The Core Laboratory of The Suzhou Cancer Center and Department of Radiotherapy, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou, Jiangsu 215001, P.R. China.
Oncol Rep. 2018 Mar;39(3):1207-1214. doi: 10.3892/or.2018.6194. Epub 2018 Jan 5.
miR-let-7a is the most widely studied miRNA, whose functions have been well-established by scientists in both carcinogenesis and progression of human cancer, including gastric cancer (GC). However, to date there is a lack of information concerning the relationship between miR-let-7a and cellular autophagy. Using western blotting and immunofluorescence, we determined that upregulation of miR-let-7a led to increased cellular autophagic level, whereas miR-let-7a suppression decreased autophagy activity in GC cells. To further elucidate the mechanisms underlying this, we screened potential targets of miR-let-7a using bioinformatics analyses, validated by a series of assays. Our results indicated that Rptor independent companion of mTOR complex 2 (Rictor) was a direct target of miR-let-7a. In addition, rescue experiments in vitro showed that miR-let-7a promoted cellular autophagic level by inhibiting Rictor expression in GC cells. Furthermore, as an upstream executor of Akt-mTOR signaling pathway, we found that Rictor elaborated its effect on autophagy by phosphorylating Akt and mTOR, and this regulatory process could also be mediated by miR-let-7a. Taken together, our results present a novel role for miR-let-7a in GC which modulates autophagy by targeting Rictor, following the regulation of Akt-mTOR signal pathway.
miR-let-7a 是研究最广泛的 miRNA，其在人类癌症的发生和进展中的作用已被科学家充分证实，包括胃癌（GC）。然而，迄今为止，关于 miR-let-7a 与细胞自噬之间的关系还缺乏信息。通过 Western blot 和免疫荧光，我们确定 miR-let-7a 的上调导致细胞自噬水平增加，而 miR-let-7a 的抑制则降低 GC 细胞中的自噬活性。为了进一步阐明这一机制，我们使用生物信息学分析筛选了 miR-let-7a 的潜在靶标，并通过一系列实验进行了验证。我们的结果表明，mTOR 复合物 2 的 Rictor 非依赖性伴侣（Rictor）是 miR-let-7a 的直接靶标。此外，体外的挽救实验表明，miR-let-7a 通过抑制 GC 细胞中 Rictor 的表达来促进细胞自噬水平。此外，作为 Akt-mTOR 信号通路的上游执行者，我们发现 Rictor 通过磷酸化 Akt 和 mTOR 来发挥其对自噬的作用，而这一调节过程也可以由 miR-let-7a 介导。综上所述，我们的研究结果揭示了 miR-let-7a 在 GC 中的新作用，通过靶向 Rictor 调节 Akt-mTOR 信号通路来调节自噬。
