TABLE 1.
Biological functions of exosomal circRNAs in cancers.
| Exosomal circRNA | Producer cell | Expression | Target miRNA (Target gene) | Function | References |
| circRNA_100284 | Arsenite-transformed hepatic epithelial cell | Upregulated | miR-271 (EZH2) | Accelerates cell cycle and promotes cell proliferation | Dai et al., 2018 |
| CDR1-AS | Hepatocellular carcinoma | Upregulated | miR-1270 (AFP) | Accelerates cell proliferation and migration | Su et al., 2019 |
| circ0000284 | Cholangiocarcinoma | Upregulated | miR-637 (LY6E) | Accelerates proliferation and migration | Wang J. et al., 2019 |
| circ-DB | Adipocyte | Upregulated | miR-34a (USP7, CCNA2) | Promotes HCC proliferation and decreases DNA damage | Zhang et al., 2019a |
| circ0051443 | Normal hepatic cells | Downregulated | miR-331-3p (BAK1) | Causes tumor cell apoptosis and cell cycle arrest | Chen W. et al., 2020 |
| circPDE8A | Pancreatic cancer | Upregulated | miR-338 (MACC1) | Promotes EMT Prognostic biomarker | Li Z. et al., 2018 |
| circRanGAP1 | Gastric cancer | Upregulated | miR-877-3p (VEGFA) | Promotes migration and invasion | Lu et al., 2020 |
| circPTGR1 | Hepatocellular carcinoma | Upregulated | miR-339a (MET) | Promotes migration and invasion | Wang G. et al., 2019 |
| circIARS | Pancreatic cancer | Upregulated | miR-122 (RhoA) | Upregulates the permeability of HUVEC cells | Li J. et al., 2018 |
| circRNA-100338 | Hepatocellular carcinoma | Upregulated | Unknown (directly bind to NOVA2) | Upregulates the permeability of HUVEC cells | Huang et al., 2020 |
| circPRMT5 | Urothelial carcinoma of the bladder | Upregulated | miR-30c (SNAIL1) | Biomarker for metastasis | Chen et al., 2018 |
| circNRIP1 | Gastric cancer | Upregulated | miR-149-5p (AKT1) | Promotes metastasis | Zhang et al., 2019 |
| circWHSC1 | Ovarian cancer | Upregulated | miR145, miR1182 (MUC1, TERT) | Promotes peritoneal dissemination | Zong et al., 2019 |
| ciRS-122 | Colorectal cancer | Upregulated | miR-122 (PKM2) | Induces chemoresistance | Wang Y. et al., 2020 |
| ciRS-133 | Gastric cancer | Upregulated | miR-133 (PRDM16) | Adipocyte browning | Zhang et al., 2019 |
| circ-0051443 | Hepatocellular carcinoma | Downregulated | miR-331-3p (BAK1) | Diagnostic biomarker (AUC 0.8089) | Chen W. et al., 2020 |
| hsa_circ_0065149 | Gastric cancer | Downregulated | Unknown | Diagnostic biomarker (AUC 0.64) | Shao et al., 2020 |
| circ-KIAA1244 | Gastric cancer | Downregulated | Unknown | Diagnostic and prognostic biomarker (AUC 0.7481) | Tang et al., 2018 |
| circ_0000419 | Gastric cancer | Downregulated | Unknown | Diagnostic biomarker (AUC 0.84) | Tao et al., 2020 |
| hsa_circ_0001946 and hsa_circ_0043603 | Esophageal squamous cell cancer | Downregulated | Unknown | Diagnostic biomarker (Sensitivity: 84%, Specificity: 98%) | Fan et al., 2019 |
| hsa-circ-0004771 | Colorectal cancer | Upregulated | Unknown | Diagnostic biomarker (AUC 0.86–0.88) | Pan et al., 2019 |
| hsa_circ_0014235 and hsa_circ_0025580 | Lung squamous cell carcinoma | Upregulated | Unknown | Diagnostic biomarker (AUC 0.8) | Wang Y. et al., 2020 |
| hsa_circRNA_0056616 | Lung adenocarcinoma | Downregulated | Unknown | Diagnostic biomarker for lymph node metastasis (AUC 0.812) | He et al., 2020 |
| FECR1 | Small cell lung carcinoma | Upregulated | miR-584 (ROCK1) | Biomarker for prognosis and response to chemotherapy | Li et al., 2019 |
| circPDAC | Pancreatic cancer | Upregulated | Unknown | Diagnostic biomarker (Sensitivity: 0.45, Specificity: 0.90) | Seimiya et al., 2020 |
| CDR1-AS | Ovarian cancer | Downregulated | miR-1270 (SCAI) | Biomarker for cisplatin resistance | Zhao Z. et al., 2019 |
| circNFIX | Glioma | Upregulated | miR-132 (ABCG2) | Induces chemoresistance Diagnostic biomarker (0.885) and prognostic biomarker | Ding et al., 2020 |
| circ_0044516 | Prostate cancer | Upregulated | miR-29a-3p (Unknown) | Diagnostic biomarker (AUC not shown) | Li et al., 2020 |
| circFNDC3B | Papillary thyroid cancer | Upregulated | miR-1178 (TLR4) | Diagnostic biomarker (AUC not shown) | Wu et al., 2020 |
| Other circRNAs determined by bioinformatic analysis | Breast cancer, endometrial cancer, pancreatic ductal adenocarcinoma, lung adenocarcinoma, papillary thyroid carcinoma | Upregulated and downregulated | Diagnostic biomarker (AUC not shown) | Xu et al., 2018; Li et al., 2019a; Wang J. et al., 2019; Yang et al., 2019; Chen F. et al., 2020 |