Fig. 1

Exosomal circSCP2 was enriched in CRC patients serum and tumor tissues. (A) Morphology and size of exosomes obtained from serum of patients with colorectal cancer under scanning electron microscope (SEM). Scale bar, 200 μm. (B) Heat maps of differentially expressed circular RNAs obtained from exosomes of three pairs of patients with early and advanced colorectal cancer. (C) qRT-PCR analysis of circSCP2 mRNA expression in serum from healthy donors, patients before, after surgery as well as patients undergo relapse (N = 10 patients/group). (D) Correlation analysis of circSCP2 mRNA expression between patient plasma exosomes and tissues. (E) qRT-PCR analysis of circSCP2 mRNA expression within 50 pairs of normal and tumor tissues. (F) qRT-PCR analysis of circSCP2 mRNA expression within tissues from CRC patients under different stages. (N = 50 patients) (G) The schematic showed the circularization and back-splicing mode of SCP2 exon 1 to form circSCP2. The back-to-back splice junction site was confirmed by Sanger sequencing using the divergent primer. (H) Agarose gel electrophoresis of PCR product amplified from cDNA and gDNA of RKO cells using convergent and divergent primers. GAPDH was used as the negative control. (I) qRT-PCR analysis of circSCP2, linear SCP2 in RKO, HCT116 and LOVO cells with or without RNase R treatment. (J) CircSCP2 and linear SCP2 expression levels were detected after actinomycin D treatment in RKO cells. (K) FISH assays showed that the spatial distribution of circSCP2 was mostly present in tumor tissues and tumors with last stages and metastatic tumors such as liver metastases also showed extremely high expression of circSCP2. Scale bar, 50 μm. (L) FISH assays showed that the sub-cellular distribution of circSCP2 was mostly present in the cytoplasm. Scale bar, 50 μm. The data were independently repeated at least three times. Differences between two groups were analyzed using Student’s t-tests