Fig. 5

CircRNA-SORE transmits sorafenib resistance by exosomes. a Exosomes were extracted from the blood of nine HCC patients prior to sorafenib treatment, and exosomal circRNA-SORE expressions were evaluated by qPCR assays. Lower and higher circRNA-SORE expressions were stratified by the average expression among the nine patients. Response to sorafenib was defined as once achieved complete response, partial response or stable disease for >3 months. b Negative staining electron micrograph of exosomes isolated from HepG2-SR culture media. Scale bar, 200 nm. c Size distribution of exosomes by NanoSight NS300 instrument. d Western blot analysis for positive exosome markers (HSP70, TSG101, CD9 and CD63) and negative exosome marker (Calnexin). e qPCR analysis of exosomal circRNA-SORE isolated from sorafenib-resistant and parental cell culture media. f qPCR analysis of circRNA-SORE isolated from sorafenib-resistant cell culture media (M) and cells (C). g Schematic showing that exosomes were isolated from parental and sorafenib-resistant cells (P-exo and SR-exo, respectively) and used to treat (30 μg) parental cells for 24 h. The exosome-treated parental cells were then transfected with si-NC or si-circRNA-SORE and treated with sorafenib for 48 h. h, i Exosomes were isolated from parental and sorafenib-resistant cells (P-exo and SR-exo, respectively) and used to treat parental cells for 24 h. The exosome-treated parental cells were then transfected with si-NC or si-circRNA-SORE and treated with sorafenib for 48 h. Charts show h qPCR results of circRNA-SORE expression and i cell viability in exosome-treated parental cells. j Schematic showing that HepG2-SR cells were treated with si-NC or si-circRNA-SORE before the culture media were harvested for exosome isolation and subsequent exosome treatments (30 μg) on HepG2 parental cells. k HepG2-SR, SKhep1-SR and LM3-SR cells were treated with si-NC or si-circRNA-SORE before the culture media were harvested for exosome isolation and subsequent exosome treatments on parental cells. The chart shows the cell viability in exosome-treated parental cells. l BALB/c nude mice (4- to 6-week-old males) were subcutaneously injected with SKhep1-P cells. On week 4, the mice were treated with sorafenib (30 mg/kg/day) by oral gavage and exosomes (80 μg twice a week for 4 weeks) from SKhep1-SR or SKhep1-P cell culture media by injection at the implantation site twice a week for 4 weeks. Animals were sacrificed on week 8 and xenografts were isolated and measured. Three independent experiments with three technical repetitions were performed. Data are expressed as mean ± SEM (error bars). Statistical analyses used Student’s t test. *p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001