Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, 710061, China.
J Exp Clin Cancer Res. 2021 Feb 17;40(1):72. doi: 10.1186/s13046-021-01868-z.
Long non-coding RNAs (lncRNAs) are widely involved in human cancers' progression by regulating tumor cells' various malignant behaviors. MAPKAPK5-AS1 has been recognized as an oncogene in colorectal cancer. However, the biological role of MAPKAPK5-AS1 in hepatocellular carcinoma (HCC) has not been explored.
Quantitative real-time PCR was performed to detect the level of MAPKAPK5-AS1 in HCC tissues and cell lines. The effects of MAPKAPK5-AS1 on tumor growth and metastasis were assessed via in vitro experiments, including MTT, colony formation, EdU, flow cytometry, transwell assays, and nude mice models. The western blotting analysis was carried out to determine epithelial-mesenchymal transition (EMT) markers and AKT signaling. The interaction between MAPKAPK5-AS1, miR-154-5p, and PLAGL2 were explored by luciferase reporter assay and RNA immunoprecipitation. The regulatory effect of HIF-1α on MAPKAPK5-AS1 was evaluated by chromatin immunoprecipitation.
MAPKAPK5-AS1 expression was significantly elevated in HCC, and its overexpression associated with malignant clinical features and reduced survival. Functionally, MAPKAPK5-AS1 knockdown repressed the proliferation, mobility, and EMT of HCC cells and induced apoptosis. Ectopic expression of MAPKAPK5-AS1 contributed to HCC cell proliferation and invasion in vitro. Furthermore, MAPKAPK5-AS1 silencing suppressed, while MAPKAPK5-AS1 overexpression enhanced HCC growth and lung metastasis in vivo. Mechanistically, MAPKAPK5-AS1 upregulated PLAG1 like zinc finger 2 (PLAGL2) expression by acting as an endogenous competing RNA (ceRNA) to sponge miR-154-5p, thereby activating EGFR/AKT signaling. Importantly, rescue experiments demonstrated that the miR-154-5p/PLAGL2 axis mediated the function of MAPKAPK5-AS1 in HCC cells. Interestingly, we found that hypoxia-inducible factor 1α (HIF-1α), a transcript factor, could directly bind to the promoter to activate MAPKAPK5-AS1 transcription. MAPKAPK5-AS1 regulated HIF-1α expression through PLAGL2 to form a hypoxia-mediated MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC.
Our results reveal a MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC progression and suggest that MAPKAPK5-AS1 could be a potential novel therapeutic target of HCC.
长链非编码 RNA（lncRNA）通过调节肿瘤细胞的各种恶性行为，广泛参与人类癌症的进展。MAPKAPK5-AS1 已被认为是结直肠癌的癌基因。然而，MAPKAPK5-AS1 在肝细胞癌（HCC）中的生物学作用尚未得到探索。
采用定量实时 PCR 检测 HCC 组织和细胞系中 MAPKAPK5-AS1 的水平。通过体外实验，包括 MTT、集落形成、EdU、流式细胞术、Transwell 测定和裸鼠模型，评估 MAPKAPK5-AS1 对肿瘤生长和转移的影响。采用 Western blot 分析检测上皮-间充质转化（EMT）标志物和 AKT 信号。通过荧光素酶报告基因测定和 RNA 免疫沉淀探索 MAPKAPK5-AS1、miR-154-5p 和 PLAGL2 之间的相互作用。通过染色质免疫沉淀评估 HIF-1α 对 MAPKAPK5-AS1 的调控作用。
MAPKAPK5-AS1 在 HCC 中表达明显上调，其过表达与恶性临床特征和生存降低有关。功能上，MAPKAPK5-AS1 敲低抑制 HCC 细胞的增殖、迁移和 EMT，并诱导细胞凋亡。外源性表达 MAPKAPK5-AS1 促进 HCC 细胞在体外的增殖和侵袭。此外，MAPKAPK5-AS1 沉默抑制体内 HCC 生长和肺转移，而 MAPKAPK5-AS1 过表达增强体内 HCC 生长和肺转移。机制上，MAPKAPK5-AS1 通过作为内源性竞争性 RNA（ceRNA）来吸收 miR-154-5p，从而上调 PLAG1 样锌指 2（PLAGL2）的表达，从而激活 EGFR/AKT 信号。重要的是，挽救实验表明，miR-154-5p/PLAGL2 轴介导了 MAPKAPK5-AS1 在 HCC 细胞中的功能。有趣的是，我们发现转录因子缺氧诱导因子 1α（HIF-1α）可以直接结合启动子激活 MAPKAPK5-AS1 转录。MAPKAPK5-AS1 通过 PLAGL2 调节 HIF-1α 表达，在 HCC 中形成缺氧介导的 MAPKAPK5-AS1/PLAGL2/HIF-1α 信号环。
我们的研究结果揭示了 HCC 进展中的 MAPKAPK5-AS1/PLAGL2/HIF-1α 信号环，并表明 MAPKAPK5-AS1 可能成为 HCC 的潜在新型治疗靶点。
