Emerging evidence suggest the critical role of circular RNAs (circRNAs) in disease development especially in various cancers. However, the oncogenic role of circRNAs in hepatocellular carcinoma (HCC) is still largely unknown. RNA sequencing was performed to identify significantly upregulated circRNAs in paired HCC tissues and non-tumor tissues. CCK-8 assay, colony formation, transwell, and xenograft mouse models were used to investigate the role of circRNAs in HCC proliferation and metastasis. Small interfering RNA (siRNA) was used to silence gene expression. RNA immunoprecipitation, biotin pull-down, RNA pull-down, luciferase reporter assay and western blot were used to explore the underlying molecular mechanisms. Hsa_circ_0095868, derived from exon 5 of the MDK gene (named circMDK), was identified as a new oncogenic circRNA that was significantly upregulated in HCC. The upregulation of circMDK was associated with the modification of N6-methyladenosine (m6A) and poor survival in HCC patients. Mechanistically, circMDK sponged miR-346 and miR-874-3p to upregulate ATG16L1 (Autophagy Related 16 Like 1), resulting to the activation of PI3K/AKT/mTOR signaling pathway to promote cell proliferation, migration and invasion. Poly (β-amino esters) (PAEs) were synthesized to assist the delivery of circMDK siRNA (PAE-siRNA), which effectively inhibited tumor progression without obvious adverse effects in four liver tumor models including subcutaneous, metastatic, orthotopic and patient-derived xenograft (PDX) models. CircMDK could serve as a potential tumor biomarker that promotes the progression of HCC via the miR-346/874-3p-ATG16L1 axis. The PAE-based delivery of siRNA improved the stability and efficiency of siRNA targeting circMDK. The PAE-siRNA nanoparticles effectively inhibited HCC proliferation and metastasis in vivo. Our current findings offer a promising nanotherapeutic strategy for the treatment of HCC.

中文翻译：

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M6A介导的circMDK上调促进肿瘤发生并作为肝细胞癌的纳米治疗靶点

新出现的证据表明环状 RNA (circRNA) 在疾病发展中的关键作用，尤其是在各种癌症中。然而，circRNA 在肝细胞癌 (HCC) 中的致癌作用仍然很大程度上未知。进行 RNA 测序以鉴定成对的 HCC 组织和非肿瘤组织中显着上调的 circRNA。CCK-8 测定、集落形成、transwell 和异种移植小鼠模型用于研究 circRNA 在 HCC 增殖和转移中的作用。小干扰 RNA (siRNA) 用于沉默基因表达。RNA 免疫沉淀、生物素下拉、RNA 下拉、荧光素酶报告基因测定和蛋白质印迹用于探索潜在的分子机制。Hsa_circ_0095868，来源于MDK基因的外显子5（命名为circMDK），被鉴定为一种新的致癌环状RNA，在HCC中显着上调。circMDK 的上调与 N6-甲基腺苷 (m6A) 的修饰和 HCC 患者的低生存率有关。机制上，circMDK 海绵化 miR-346 和 miR-874-3p 上调 ATG16L1（自噬相关 16 Like 1），从而激活 PI3K/AKT/mTOR 信号通路，促进细胞增殖、迁移和侵袭。合成聚（β-氨基酯）（PAEs）以辅助递送circMDK siRNA（PAE-siRNA），在皮下、转移性、原位和患者来源的异种移植物四种肝肿瘤模型中有效抑制肿瘤进展且无明显不良反应(PDX) 模型。CircMDK 可以作为一种潜在的肿瘤生物标志物，通过 miR-346/874-3p-ATG16L1 轴促进 HCC 的进展。基于 PAE 的 siRNA 递送提高了 siRNA 靶向 circMDK 的稳定性和效率。PAE-siRNA纳米颗粒在体内有效抑制HCC增殖和转移。我们目前的研究结果为治疗 HCC 提供了一种有前景的纳米治疗策略。