PTPRC and colorectal carcinoma: To determine the source of circRHOBTB3 in serum exosomes, we detected circRHOBTB3 expression in CRC cell lines (RKO, HCT116, HCT8, DLD1 and SW480), a normal intestinal epithelial cell line (NCM460), a fibroblast cell line (HELF), immune-related cell lines (THP-1 and Jurkat), and CD45+ cells from a healthy donor.