Exosomal circRNA-MANBA mediates sorafenib resistance of hepatocellular carcinoma via miR-1290/CD109/p-STAT3 (Ser727) axis

Circular RNAs (circRNAs) are increasingly gaining importance and attention due to their diverse potential functions. Our study aims to explore the novel mechanisms by which exosome-contained circRNAs promote sorafenib resistance in hepatocellular carcinoma (HCC). Here we report that a circular RNA, circRNA-MANBA (a circular RNA upregulated in exosomes derived from sorafenib-resistant HCC cells), plays a significant role in sorafenib resistance in HCC. We identified that circRNA-MANBA is increased in sorafenib-resistant HCC cells, their exosomes, and tumor samples from sorafenib-treated HCC patients. Depletion of circRNA-MANBA substantially increases the cell-killing ability of sorafenib. Co-culture experiments revealed that exosomes from sorafenib-resistant HCC cells carrying large amounts of circRNA-MANBA could transmit drug resistant capacity to parental cells. Further studies revealed that circRNA-MANBA acted as ‘miRNAs sponge’ to absorb miR-1290, which prevented miR-1290 interaction with CD109 and thus upregulated STAT3 phosphorylation subsequently. Using different HCC mouse models, we demonstrated that silencing circRNA-MANBA by injection of siRNA could substantially overcome sorafenib resistance. Our study provides a proof-of-concept demonstration for a potential strategy to overcome sorafenib resistance in HCC patients by targeting circRNA-MANBA. Exosomes of parental HCC cells (Hep3B, PLC/PRF/5, Huh7) and sorafenib-resistant HCC cells (Hep3B-R, PLC/PRF/5-R, Huh7-R) were isolated by standard centrifugation steps. Total RNAs from exosomes of parental and sorafenib-resistant HCC cells were transcribed into fluorescent cRNA utilizing a random priming method (Arraystar Super RNA Labeling Kit; Arraystar). The labeled cRNAs were hybridized onto the Arraystar Human circRNA Array V2 (8x15K, Arraystar). After having washed the slides, the arrays were scanned by the Agilent Scanner G2505C.