M6A-mediated upregulation of circMDK promotes tumorigenesis and acts as a nanotherapeutic target in hepatocellular carcinoma

Abstract

Background 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. Methods 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. Results 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. Conclusions 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. Graphical Abstract

Comprehensive Analysis of the Transcriptome-wide m6A Methylome in Lung Adenocarcinoma by MeRIP Sequencing

“…m6A modification is a dynamic and reversible methylation modification regulated by the m6A regulators, which is mainly composed of "writers" (METTL3, METTL14), and "erasers" (ALKBH5, FTO), and "readers" (YTHDFs, YTHDCs, IGF2BPs) (10). Increasing studies have confirmed that m6A modification plays an important role in malignant tumors (11,12). For instance, m6A reader YTHDF1 promotes the proliferation, migration, invasion, and cell cycle of hepatocellular carcinoma cells by activating the PI3K/AKT/mTOR signaling pathway (13).…”

The role of N6-methyladenosine-modified non-coding RNAs in the pathological process of human cancer

“…In recent years, researchers have found that m6A-modified ncRNAs are involved in cancer metastasis. For example, m6A-modified circMDK was significantly upregulated in HCC and could promote cancer metastasis in vivo and in vitro [ 122 ]. Therefore, we believe that m6A-modified ncRNAs play a role in the process of cancer metastasis, which suggests that m6A-modified ncRNAs may be used in clinical diagnosis to predict cancer metastasis.…”

Emerging Role of Noncoding RNAs in EGFR TKI-Resistant Lung Cancer

“…Apart from miRNAs, lncRNAs such as H19 and LINC00152 regulate the phosphorylation of AKT to restore erlotinib resistance [ 40 , 41 ]. Furthermore, dysregulated circRNAs serve as miRNA sponges to inactivate PI3K/AKT proteins [ 42 , 43 ], but their mechanisms remain unclear.…”