Ying-Qiao Wang's research while affiliated with First Affiliated Hospital of China Medical University and other places

Background Advanced hepatocellular carcinoma (HCC) can be treated with sorafenib, which is the primary choice for targeted therapy. Nevertheless, the effectiveness of sorafenib is greatly restricted due to resistance. Research has shown that exosomes and circular RNAs play a vital role in the cancer’s malignant advancement. However, the significance of exosomal circular RNAs in the development of resistance to sorafenib in HCC remains uncertain. Methods Ultracentrifugation was utilized to isolate exosomes (Exo-SR) from the sorafenib-resistant HCC cells’ culture medium. Transcriptome sequencing and differential expression gene analysis were used to identify the targets of Exo-SR action in HCC cells. To identify the targets of Exo-SR action in HCC cells, transcriptome sequencing and analysis of differential expression genes were employed. To evaluate the impact of exosomal circUPF2 on resistance to sorafenib in HCC, experiments involving gain-of-function and loss-of-function were conducted. RNA pull-down assays and mass spectrometry analysis were performed to identify the RNA-binding proteins interacting with circUPF2. RNA immunoprecipitation (RIP), RNA pull-down, electrophoretic mobility shift assay (EMSA), immunofluorescence (IF) -fluorescence in situ hybridization (FISH), and rescue assays were used to validate the interactions among circUPF2, IGF2BP2 and SLC7A11. Finally, a tumor xenograft assay was used to examine the biological functions and underlying mechanisms of Exo-SR and circUPF2 in vivo. Results A novel exosomal circRNA, circUPF2, was identified and revealed to be significantly enriched in Exo-SR. Exosomes with enriched circUPF2 enhanced sorafenib resistance by promoting SLC7A11 expression and suppressing ferroptosis in HCC cells. Mechanistically, circUPF2 acts as a framework to enhance the creation of the circUPF2-IGF2BP2-SLC7A11 ternary complex contributing to the stabilization of SLC7A11 mRNA. Consequently, exosomal circUPF2 promotes SLC7A11 expression and enhances the function of system Xc- in HCC cells, leading to decreased sensitivity to ferroptosis and resistance to sorafenib. Conclusions The resistance to sorafenib in HCC is facilitated by the exosomal circUPF2, which promotes the formation of the circUPF2-IGF2BP2-SLC7A11 ternary complex and increases the stability of SLC7A11 mRNA. Focusing on exosomal circUPF2 could potentially be an innovative approach for HCC treatment. Graphical Abstract

Exosomes contribute substantially to the communication between tumor cells and normal cells. Benefiting from the stable structure, circular RNAs (circRNAs) are believed to serve an important function in exosome-mediated intercellular communication. Here, we focused on circRNAs enriched in starvation-stressed hepatocytic exosomes and further investigated their function and mechanism in hepatocellular carcinoma (HCC) progression. Differentially expressed circRNAs in exosomes were identified by RNA sequencing, and circTGFBR2 was identified and chosen for further study. The molecular mechanism of circTGFBR2 in HCC was demonstrated by RNA pulldown, RIP, dual-luciferase reporter assays, rescue experiments and tumor xenograft assay both in vitro and vivo. We confirmed exosomes with enriched circTGFBR2 led to an upregulated resistance of HCC cells to starvation stress. Mechanistically, circTGFBR2 delivered into HCC cells via exosomes serves as a competing endogenous RNA by binding miR-205-5p to facilitate ATG5 expression and enhance autophagy in HCC cells, resulting in resistance to starvation. Thus, we revealed that circTGFBR2 is a novel tumor promoter circRNA in hepatocytic exosomes and promotes HCC progression by enhancing ATG5-mediated protective autophagy via the circTGFBR2/miR-205-5p/ATG5 axis, which may be a potential therapeutic target for HCC.