Lnc-GAN1 表达与良好的生存相关，并通过海绵吸附 mir-26a-5p 来激活 PTEN 信号通路从而抑制非小细胞肺癌的肿瘤进展。

BACKGROUND: Long non-coding RNAs (lncRNAs) play vital roles in the development and progression of non-small-cell lung cancer (NSCLC); however, the role of most lncRNAs in NSCLC remains unknown. This study explored the clinical significance, biological function and underlying mechanism of lnc-GAN1 in NSCLC. METHODS: With a custom lncRNA microarray we found that lnc-GAN1 is markedly downregulated in NSCLC tissues. Then lnc-GAN1 expression level was measured using qRT-PCR in NSCLC tissues and cell lines. Survival was assessed using the Kaplan-Meier method. The biological functions of lnc-GAN1 in lung cancer cells were evaluated in vitro and in vivo. RNA fluorescence in situ hybridization and subcellular localization assays revealed the subcellular distribution of lnc-GAN1 in cells. Bioinformatic analysis was adopted to predict miRNAs and signaling pathways regulated by lnc-GAN1. RNA immunoprecipitation and Dual-luciferase reporter assays were used to assess the interaction between lnc-GAN1 and miR-26a-5p in lung cancer cells. RESULTS: lnc-GAN1 is downregulated in HCC tissues and associated with larger tumor size and poor overall survival and disease-free survival; its ectopic expression suppresses cell proliferation, colony formation, and cell cycle progression and induces apoptosis in NSCLC cells; it also inhibits tumor growth in the NSCLC xenograft model. We further proved that lnc-GAN1 is localized in cytoplasm and transcribed independently from its parental gene GAN. Mechanistically, lnc-GAN1 acts as a sponge for miR-26a-5p by two seed sequences, and the two non-coding RNAs have a negative relationship in NSCLC tissues; we further prove that PTEN is a direct target of miR-26a-5p and lnc-GAN1 inhibits cell cycle signaling pathway by activating PTEN, whose expression level correlated negatively with miR-26a-5p level but positively with lnc-GAN1 level in NSCLC samples. CONCLUSIONS: Lnc-GAN1 is downregulated and associated with poor survival of NSCLC patients, and mechanistically acts as a tumor suppressor via sponging and inhibiting miR-26a-5p to upregulate PTEN. This study provides a potential prognostic biomarker and treatment target for NSCLC.

背景：长链非编码 RNA（lncRNAs）在非小细胞肺癌（NSCLC）的发生和发展中发挥着重要作用；然而，大多数 lncRNAs 在 NSCLC 中的作用仍然未知。本研究探讨了 lnc-GAN1 在 NSCLC 中的临床意义、生物学功能和潜在机制。

方法：通过定制的 lncRNA 微阵列，我们发现 lnc-GAN1 在 NSCLC 组织中显著下调。然后使用 qRT-PCR 测量 NSCLC 组织和细胞系中的 lnc-GAN1 表达水平。使用 Kaplan-Meier 法评估生存情况。在体外和体内评估 lnc-GAN1 对肺癌细胞的生物学功能。RNA 荧光原位杂交和亚细胞定位实验显示 lnc-GAN1 在细胞中的亚细胞分布。采用生物信息学分析预测 lnc-GAN1 调控的 miRNA 和信号通路。采用 RNA 免疫沉淀和双荧光素酶报告基因检测评估 lnc-GAN1 与 miR-26a-5p 在肺癌细胞中的相互作用。

结果：lnc-GAN1 在 HCC 组织中下调，与较大的肿瘤大小和不良的总生存和无病生存相关；其异位表达抑制 NSCLC 细胞的增殖、集落形成和细胞周期进程，并诱导细胞凋亡；它还抑制 NSCLC 异种移植模型中的肿瘤生长。我们进一步证明 lnc-GAN1 定位于细胞质中，并且与它的母基因 GAN 独立转录。机制上，lnc-GAN1 通过两个种子序列充当 miR-26a-5p 的海绵，并且这两个非编码 RNA 在 NSCLC 组织中呈负相关关系；我们进一步证明，PTEN 是 miR-26a-5p 的直接靶标，lnc-GAN1 通过激活 PTEN 抑制细胞周期信号通路，PTEN 的表达水平与 NSCLC 样本中的 miR-26a-5p 水平呈负相关，与 lnc-GAN1 水平呈正相关。

结论：lnc-GAN1 下调与 NSCLC 患者的不良生存相关，其机制是通过海绵吸附和抑制 miR-26a-5p 来上调 PTEN，从而发挥肿瘤抑制作用。本研究为 NSCLC 提供了一个潜在的预后生物标志物和治疗靶点。